Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3793_Библиотеки_им_академика_М_И_Перельмана
.pdf
CHAPTER 22 Cardiorenal Syndrome Type 1 222.e3
https://t.me/medicina_free
without persistent ST-segment elevation: the Task Force for the
Management of Acute Coronary Syndromes (ACS) in Patients
Presenting without Persistent ST-Segment Elevation of the
European Society of Cardiology (ESC). Eur Heart J.
2011;32:2999–3054.
70. Jneid H, Anderson JL, Wright RS, et al. 2012 ACCF/AHA focused
update of the guideline for the management of patients with
unstable angina/non-ST-elevation myocardial infarction
(updating the 2007 guideline and replacing the 2011 focused
update): a report of the American College of Cardiology
Foundation/American Heart Association Task Force on Practice
Guidelines. J Am Coll Cardiol. 2012;60:645–681.
71. Steg PG, James SK, Atar D, et al. ESC guidelines for the
management of acute myocardial infarction in patients
presenting with ST-segment elevation: the Task Force on the
Management of ST-Segment Elevation Acute Myocardial
Infarction of the European Society of Cardiology (ESC). Eur
Heart J. 2012;33:2569–2619.
72. KDIGO Group. KDIGO clinical practice guideline for acute
kidney injury. Kidney Int Suppl. 2012;2:1–115.
73. Davenport A, Anker SD, Mebazaa A, et al. ADQI 7: the clinical
management of the Cardio-Renal syndromes: work group
statements from the 7th ADQI Consensus Conference. Nephrol
Dial Transplant. 2010;25:2077–2089.
74. McCullough PA, Haapio M, Mankad S, et al. Prevention of
cardiorenal syndromes: work group statements from the 7th
ADQI Consensus Conference. Nephrol Dial Transplant.
2010;25:1777–1784.
75. Hunt SA. ACC/AHA 2005 guideline update for the diagnosis and
management of chronic heart failure in the adult: a report of the
American College of Cardiology/American Heart Association
Task Force on Practice Guidelines (Writing Committee to
Update the 2001 Guidelines for the Evaluation and Management
of Heart Failure). J Am Coll Cardiol. 2005;46:e1–e82.
76. Mehran R, Aymong ED, Nikolsky E, et al. A simple risk score for
prediction of contrast-induced nephropathy after percutaneous
coronary intervention: development and initial validation. J Am
Coll Cardiol. 2004;44:1393–1399.
77. Thakar CV, Arrigain S, Worley S, Yared JP, Paganini EP. A clinical
score to predict acute renal failure after cardiac surgery. J Am Soc
Nephrol. 2005;16:162–168.
78. Drawz PE, Miller RT, Sehgal AR. Predicting hospital-acquired
acute kidney injury—a case-controlled study. Ren Fail.
2008;30:848–855.
79. Cruz DN. Cardiorenal syndrome in critical care: the acute
cardiorenal and renocardiac syndromes. Adv Chronic Kidney Dis.
2013;20:56–66.
80. Kiernan MS, Udelson JE, Sarnak M, Konstam M. Cardiorenal
syndrome: prognosis and treatment. Gottlieb SS, ed. UpToDate.
Waltham, MA: UpToDate Inc. http://www.uptodate.com
(Accessed on October 25, 2017.).
81. House AA, Anand I, Bellomo R, et al; for the Acute Dialysis
Quality Initiative (ADQI) Consensus Group. Definition and
classification of cardio-renal syndromes: workgroup statements
from the 7th ADQI Consensus Conference. Nephrol Dial
Transplant. 2010;25:1416–1420.
82. Testani JM, Brisco MA, Chen J, et al. Timing of
hemoconcentration during treatment of acute decompensated
heart failure and subsequent survival: importance of sustained
decongestion. J Am Coll Cardiol. 2013;62:516–524.
83. Greene SJ, Gheorghiade M, Vaduganathan M, et al.
Haemoconcentration, renal function, and post-discharge
outcomes among patients hospitalized for heart failure with
reduced ejection fraction: insights from the EVEREST trial. Eur J
Heart Fail. 2013;15:1401–1411.
84. Yancy CW, Jessup M, Bozkurt B, et al. 2013 ACCF/AHA
guideline for the management of heart failure: executive
summary: a report of the American College of Cardiology
Foundation/American Heart Association Task Force on practice
guidelines. Circulation. 2013;128:1810–1852.
85. Howard PA, Dunn MI. Aggressive diuresis for severe heart failure
in the elderly. Chest. 2001;119:807–810.
86. Salvador DR, Rey NR, Ramos GC, Punzalan FE. Continuous
infusion versus bolus injection of loop diuretics in congestive
heart failure. Cochrane Database Syst Rev. 2005;(3):CD003178.
87. Felker GM, Lee KL, Bull DA, et al. Diuretic strategies in patients
with acute decompensated heart failure. N Engl J Med.
2011;364:797–805.
88. Costanzo MR, Guglin ME, Saltzberg MT, et al. Ultrafiltration
versus intravenous diuretics for patients hospitalized for acute
decompensated heart failure. J Am Coll Cardiol.
2007;49:675–683.
89. Bart BA, Goldsmith SR, Lee KL, et al. Ultrafiltration in
decompensated heart failure with cardiorenal syndrome. N Engl
J Med. 2012;367:2296–2304.
90. Costanzo MR, Johannes RS, Pine M, et al. The safety of
intravenous diuretics alone versus diuretics plus parenteral
vasoactive therapies in hospitalized patients with acutely
decompensated heart failure: a propensity score and
instrumental variable analysis using the Acutely Decompensated
Heart Failure National Registry (ADHERE) database. Am Heart
J. 2007;154:267–277.
91. O’Connor CM, Starling RC, Hernandez AF, et al. Effect of
nesiritide in patients with acute decompensated heart failure. N
Engl J Med. 2011;365:32–43.
92. Chen HH, Anstrom KJ, Givertz MM, et al. Low-dose dopamine
or low-dose nesiritide in acute heart failure with renal
dysfunction: the ROSE acute heart failure randomized trial.
JAMA. 2013;310:2533–2543.
OUTLINE
https://t.me/medicina_free
Definition, 223
Epidemiology, 224
Demographics, 225
Pathophysiology, 225
Mechanisms of Ventricular Fibrillation, 225
Pathologic Substrates, 225
Functional Modulators, 226
Transient Ischemia, 226
Hemodynamic Deterioration, 226
Metabolic Disturbances, 226
Altered Systemic Autonomic Balance, 226
Drug Toxicity, 227
Etiologies, 227
Coronary Artery Disease, 227
Nonatherosclerotic Coronary Artery Disease, 227
Coronary Artery Anomalies, 228
Vasculitis, 228
Myocardial Bridging, 228
Coronary Artery Spasm, 228
Coronary Artery Dissection, 228
Myocardial Disease, 228
Hypertrophic Cardiomyopathy, 228
Nonischemic Dilated Cardiomyopathy, 228
Arrhythmogenic Right Ventricular Cardiomyopathy, 229
Valvular Heart Disease, 230
Inflammatory and Infiltrative Disorders, 230
Congenital Heart Disease, 230
Wolff-Parkinson-White Syndrome, 231
Cardiac Conduction System Abnormalities, 231
Inherited Arrhythmic Disorders, 231
Long QT Syndrome, 231
Short QT Syndrome, 234
Brugada Syndrome, 234
23
Sudden Cardiac Death
Jodi Zilinski, Masood Akhtar
Catecholaminergic Polymorphic Ventricular
Tachycardia, 234
Clinical Presentation, 235
Initial Management of the Sudden Cardiac Arrest
Survivor, 235
Evaluation of the Sudden Cardiac Arrest Survivor, 235
Immediate Evaluation, 236
History and Physical, 236
Electrocardiogram, 236
Laboratory Testing, 236
Evaluation for Structural Heart Disease, 236
Cardiac Catheterization, 236
Echocardiography, 236
Cardiac Magnetic Resonance Imaging, 236
Evaluation for a Primary Electrical Disorder, 236
Signal-Averaged Electrocardiography, 236
Exercise Stress Testing, 237
Pharmacologic Challenge, 237
Ambulatory Electrocardiogram Monitoring, 237
Electrophysiology Study, 237
Genetic Testing, 237
Therapy, 238
Pharmacologic Therapy, 238
Myocardial Revascularization and Arrhythmia
Surgery, 238
Catheter Ablation, 239
Automated External Defibrillator, 239
Implantable Cardioverter Defibrillator, 239
Indications for Implantable Cardioverter
Defibrillators, 240
Wearable Automatic Defibrillator, 242
Conclusion, 242
Cardiovascular disease is one of the most common causes of
death, accounting for approximately 1 of every 2.9 deaths in the
United States1 and approximately 17 million deaths worldwide
each year.2 Of deaths due to a cardiovascular cause, more than
50% occur suddenly, making sudden cardiac death (SCD) one of
the most common causes of death in the United States.3 Despite
advances in the understanding of cardiac pathophysiology,
the implementation of primary and secondary prevention of
sudden cardiac death, and improvements in resuscitation and
postresuscitation care, SCD remains a major clinical and public
health concern.
DEFINITION
There are multiple purported definitions for SCD; however, it
is generally defined as the sudden cessation of cardiac activity
223
CHAPTER 23 Sudden Cardiac Death 223.e1
https://t.me/medicina_free
Keywords
sudden cardiac death
arrhythmia
cardiac arrest
implantable cardioverter defibrillator
ventricular fibrillation
ventricular tachycardia
224 PART IV Noncoronary Diseases: Diagnosis and Management
6:02 A.M.
https://t.me/medicina_free
associated with rapid hemodynamic collapse within 1 hour of
the onset of symptoms in the absence of an apparent extracardiac
cause.4 Although sudden cardiac arrest (SCA) is used to describe
a nonfatal cardiac event, SCD is conventionally used in the literature to define both fatal and nonfatal cardiac arrests. A limitation of this definition is that events are rarely witnessed, thus
the duration of symptoms is not known in approximately
one-third of cases. If the death is not witnessed, the term SCD
still applies when the victim was observed to be in his or her
usual state of health 24 hours before the event.
2
EPIDEMIOLOGY
Estimates of the incidence of SCD vary widely depending on the
source of data, definition used, and methods for extrapolation,
ranging from 180,000 to greater than 450,000.
rates further limit the ability to determine the true incidence
and cause of SCD. As the majority of out-of-hospital SCAs occur
in individuals not monitored, the exact mechanism leading to a
cardiovascular collapse is often difficult to establish. A cause is
thus assigned on the basis of presentation and the earliest available
rhythm recordings. In monitored victims and cases with a short
5,6
Low autopsy
delay between the time of collapse and rhythm identification,
ventricular fibrillation (VF) or ventricular tachycardia (VT)
historically have been identified as the most common initial
rhythms (observed approximately 75% to 80% of the time).7 With
advances in the treatment of coronary artery disease (CAD) and
an increase in the use of prophylactic implantable cardioverter
defibrillators (ICDs), VT/VF presently account for less than 30% of
the initial rhythms identified during out-of-hospital cardiac arrests
(OHCA). Rather, pulseless electrical activity (PEA) is increasingly
identified as the initial rhythm, with some series observing PEA
in 25% of OHCA events.8 Another proposed explanation for
the declining rates of VF being identified as the initial rhythm
is that the aging population has increased comorbidities and
modern treatments have increased the prevalence of end-stage
cardiovascular disease. This results in older, sicker patients who
are more likely to have acute triggers for PEA (i.e., metabolic,
respiratory) and are less likely to sustain VT/VF until emergency
medical services (EMS) arrival.9 In the setting of unmonitored
collapse, asystole is the most common initial rhythm. However,
the initial rhythm correlates with the duration of the event as
VF is seen early after collapse and degenerates to asystole as
time passes (Fig. 23.1).
6:05
6:07
6:11
Fig. 23.1 Fortuitous Holter recording from a patient who experienced sudden cardiac death
outside the hospital documents the usual and typical sequence of events. The initial rapid ventricular tachycardia continues into the second panel with widening of the QRS, probably owing
to myocardial metabolic changes. Subsequent degeneration to ventricular fibrillation is shown
in the third panel, followed by asystole in the fourth panel. The prognosis depends on the initial
documented rhythm and how soon emergency personnel arrive to treat the individual. (Modified
from National Heart, Lung, and Blood Institute. What Is An Implantable Cardioverter Defibrillator?
https://www.nhlbi.nih.gov/health/health-topics/topics/icd.)
CHAPTER 23 Sudden Cardiac Death 225
https://t.me/medicina_free
Recent advances in cardiopulmonary resuscitation (CPR) and
postresuscitation care have improved survival rates from OHCA.
A prospective clinical registry of OHCA survivors in the United
States reported an increased survival rate to hospital discharge
from 5.7% in 2005 to 8.3% in 2012.10 Even with advances in the
treatment of cardiovascular disease and improvements in the
performance and availability of CPR, the long-term outcome of
SCA victims remains poor, with the prognosis strongly influenced
by the initial rhythm at the time of cardiac arrest. Survival rates
are higher for individuals in whom VF is the initial rhythm, with
approximately 30% surviving to hospital discharge. Nonshockable
rhythms—such as PEA, bradycardia, or asystole—have been
associated with poor long-term survival rates (8% for PEA).
DEMOGRAPHICS
The risk of suffering an SCA varies with a number of factors,
increases dramatically with age, and is overwhelmingly more
common in the setting of underlying structural heart disease.
The majority of SCDs occur in adults, with approximately 1%
occurring in individuals younger than age 35 years.5 However,
the proportion of deaths that are sudden is elevated in younger
age groups. The presence of underlying structural heart disease
results in a 6- to 10-fold increase in the risk of SCA. Furthermore,
SCD is the mechanism of death in approximately 60% of patients
with known coronary heart disease (CHD)
initial clinical manifestation of CHD in 15% of patients.13 Autopsy
studies suggest that 21% to 45% of victims of SCD have a normal
cardiac postmortem examination.
The incidence of SCD also varies by sex and race. Men are 2
to 3 times more likely to experience SCA than women, even
when adjusting for predisposing conditions.16 Compared to men,
women who experience a cardiac arrest are more likely to be
older, to present with PEA, and to have a cardiac arrest at home.17
In regard to survival from SCA, women—especially younger
women—have increased rates of successful resuscitation and
survival from shockable rhythms than men.
Variations in rates of SCD and survival from SCA have been
observed in different racial and ethnic populations. African
Americans, as opposed to whites, have been documented to have
higher rates of SCD and worse rates of survival from SCA, in
part owing to their increased likelihood of suffering an unwitnessed cardiac arrest or documentation of PEA as the initial
rhythm at the time of cardiac arrest.
completely account for worsened survival rates, as the rate of
survival to hospital discharge in African-American SCA victims
with VT/VF documented as the initial rhythm is 27% lower than
the survival rate in white patients.22 Possible contributing factors
for worsened survival rates include African-American patients
receiving treatment at hospitals with worse outcomes and a
decreased likelihood that patients in low-income AfricanAmerican neighborhoods will receive bystander-initiated CPR
than victims in high-income, white neighborhoods.
PATHOPHYSIOLOGY
The epidemiology of SCD is intertwined with the pathophysiology
underlying the event. SCD may be considered as the outcome
11,12
and SCA is the
14,15
17,18
19–21
However, this does not
22,23
of an interaction between an abnormal cardiac substrate and a
transient functional disturbance that triggers the arrhythmia at
a specific point in time. In the absence of demonstrable structural
heart disease, inheritable arrhythmic conditions are more commonly being identified as potential substrates for SCA. With the
increased availability of genetic testing, genetic mutations are
increasingly demonstrated as the etiology for SCA, with a decreasing proportion of SCA being classified as idiopathic.
Mechanisms of Ventricular Fibrillation
VF has been postulated to be the result of multiple localized areas
of microreentry in the absence of any organized electrical activity24
7
and is often depicted as rotating spiral waves.25 It has also been
proposed that in the setting of structural heart disease or abnormal
depolarization and/or repolarization from a channelopathy, there
is diffuse, heterogenous myocardial depolarization and dispersion
of electrical activity that creates the electrophysiologic substrate
for reentry. Although the structure to accommodate reentry may
be present in a heart, a trigger event is typically required to
initiate an arrhythmia in the vulnerable heart.
26
The aforementioned myocardial heterogeneity results in
fragmentation of impulse conduction with multiple focal spiral
wavelets of myocardial activation. On the electrocardiogram
(ECG), this localized reentry is depicted by high-frequency
undulating waves that are irregular in amplitude, morphology,
and cycle length. These uncoordinated localized wavelets do not
result in organized electrical activity; thus no myocardial depolarization or contraction is generated, resulting in an absence
of cardiac output and presence of global ischemia. With prolonged
VF, there is worsened ischemia and acidosis, which is manifested
on the ECG by an increase in fibrillation cycle length, and the
fibrillation waves may ultimately become so fine that electrical
activity is not apparent.
27,28
Pathologic Substrates
The common thread to the underlying mechanism of VT/VF is
the concept of heterogeneity in myocardial structure resulting in
abnormal depolarization and/or repolarization. There are multiple
different etiologies that result in heterogeneous myocardial structure and function, creating a potential pathologic substrate for
SCA. When a person experiences SCD, especially in the setting
of preexisting structural heart disease, the presumed mechanism
is electrical instability with a trigger of ischemia or some other
arrhythmogenic stimulus that induces a lethal arrhythmia that
leads to hemodynamic collapse. However, as PEA has become
increasingly identified as the initial rhythm at time of OHCA,
proportion of SCDs may be the result of abrupt hemodynamic
collapse without a preceding lethal arrhythmia.
While variations in the reporting of SCD events and the rarity
of autopsy limits the reliability of estimates on the etiology of
SCD, CHD remains the most common contributing factor in
SCA cases (present in 70% to 75%).3 Other structural cardiac
abnormalities, such as dilated cardiomyopathy (DCM) and
hypertrophic cardiomyopathy (HCM), are responsible for the
second largest proportion of SCA cases. Despite extensive clinical
evaluation in SCA survivors or autopsy in SCD victims, no
significant cardiac abnormality is identified in approximately
5% of SCA cases.
29,30
8
a
226 PART IV Noncoronary Diseases: Diagnosis and Management
https://t.me/medicina_free
Coronary lesions have been identified in up to 90% of SCD
victims,31 although CHD may present as an acute, chronic, or
acute-on-chronic process. Acutely, in the setting of plaque erosion,
platelet aggregation, and thrombosis, individuals with the rapid
onset of ischemia may present with a lethal arrhythmia. Only
20% of SCD victims are identified as suffering from an acute
myocardial infarction (MI) at the time of cardiac arrest.32 In the
setting of chronic CHD, myocardial scars from previous MIs are
more reflective of the source pathology in SCA.
33
DCM represents the underlying pathology in approximately
10% to 19% of SCD victims depending on the population
evaluated. In DCM, interstitial patchy fibrosis, myocyte degeneration, and necrosis contribute to the formation of heterogeneous
areas of electrical conduction involved in the mechanism of
reentry in VT/VF. Left ventricular hypertrophy (LVH) is an
independent risk factor for SCD and the majority of SCA victims
with CHD have coexisting LVH. The pathophysiology underlying
this increased risk is related to altered membrane electrophysiology
(EP) with delayed inactivation of slow inward Ca2+ currents and
delayed activation of K+ rectifier currents affecting the action
potential in hypertrophied ventricular myocytes. Furthermore,
transient ischemia increases the susceptibility of hypertrophied
myocytes to delayed afterdepolarizations and triggered arrhythmias. In HCM, pathologic examination demonstrates myofibrillar
disarray that also contributes to myocardial heterogeneity.
Infiltrative, inflammatory valvular diseases and congenital
cardiac lesions account for a minority of SCA events in patients
with structural heart disease. Infiltrative diseases, such as sarcoidosis and amyloidosis, are associated with an increased risk
of SCD due to both arrhythmia and pump failure. In the case
of sarcoidosis, EP studies in patients with cardiac sarcoidosis
have demonstrated multiple inducible VTs. The mechanism is
felt to be consistent with scar-mediated reentry, with possible
contributions from inflammation triggering ventricular ectopy
or slowed conduction in granulomatous scar.34 In young adults,
acute viral myocarditis is among the more common causes of
SCD,35 with high-grade inflammatory processes in the myocardium contributing to diffuse fibrosis36 that acts as a substrate
for arrhythmia. Congenital cardiac lesions, such as anomalous
coronary arteries, are associated with an increased risk of SCD.
In addition, SCD is also one of the leading causes of death in
adults with congenital heart disease, accounting for 7% of all
deaths in one series.
37
Structural abnormalities of the cardiac conducting tissue are
best exemplified by the Wolff-Parkinson-White (WPW) syndrome
and diseases of the His-Purkinje system. Patients with WPW
syndrome who have pathways with short refractory periods are
susceptible to VF during atrial fibrillation/flutter. There is an
increased risk of SCD in individuals with disease within the
His-Purkinje system related to an increased risk of VT rather
than bradyarrhythmic events.
38
While genetically determined disorders account for a small
proportion of SCDs (1%–3%),35 they are more likely than
CHD to be the cause of SCD in young adults. Some of the
inheritable arrhythmic disorders include long QT syndrome,
short QT syndrome, Brugada syndrome, arrhythmogenic right
ventricular cardiomyopathy (ARVC), HCM, and catecholaminergic
polymorphic ventricular tachycardia (CPVT).39 Identification
of these inheritable arrhythmic conditions is important in the
event of SCA or SCD, as it can provide valuable information
and affect clinical management of the survivor of an SCA plus
prevent future events in family members.
Functional Modulators
While a pathologic substrate is typically required to sustain an
arrhythmia, the initiation of a fatal arrhythmia often is the result
of the interaction between the underlying structural abnormality
and a functional modulator converting stable abnormalities in
electrical conduction to an unstable state. Functional modulators,
such as transient ischemia or acquired long QT, can even initiate
a fatal arrhythmia in the absence of structural heart disease,
particularly in the setting of an intense stimulus or profoundly
abnormal disturbances. While possible, clinically fatal arrhythmias
less commonly present in the structurally normal heart. Some
of the functional abnormalities that can contribute to initiation
of a potentially fatal arrhythmia are described next.
Transient Ischemia. Ischemia plays a major role in producing
fatal arrhythmias. Some of the contributing factors at the cellular
level resulting from acute ischemia include dispersion of both
conduction patterns and refractoriness, providing the environment
for reentrant arrhythmias and generating abnormal automatic
activity. Ischemia contributes to heterogeneity in the myocardium
by preferentially opening the ATP-sensitive K+ channels in the
epicardial cells as opposed to the endocardial cells. The resulting
heterogeneous refractoriness increases the susceptibility of the
myocardium to arrhythmias. Reperfusion events also may
contribute to arrhythmias as, during reperfusion, an inward flux
of calcium results in calcium overload and correlates with a
burst of spontaneous ventricular ectopy, possibly resulting from
automaticity or triggered activity.
Hemodynamic Deterioration. A cardiac arrest may be precipi-
tated by acute hemodynamic deterioration, possibly as a result
of ischemia and/or alteration of metabolic substrates. In the
setting of hemodynamic deterioration, cardiac arrest carries a
high short-term mortality rate. Hypoxemia can also result in
ischemia and alteration of metabolic substrates contributing to
SCD. Furthermore, a hypoxemic event often precedes a bradycardic and/or asystolic arrest.
Metabolic Disturbances. Hypokalemia and hyperkalemia have
been implicated in an increased risk of SCD and total cardiovascular mortality. Both hypokalemia and hypomagnesemia play
a role in the genesis of torsades de pointes (TdP) and other
polymorphic VT. Similarly, acidosis has been shown to be a
contributing factor to SCD and correction of acidosis is one of
the central tenets in the resuscitation of PEA.
Altered Systemic Autonomic Balance. Structural abnormalities,
particularly those resulting in cardiomyopathy and systolic heart
failure, affect the neurohormonal milieu generating autonomic
disturbances that result in altered β-adrenergic receptor content,
coupling proteins, and adenylate cyclase activity. The resulting
CHAPTER 23 Sudden Cardiac Death 227
CAD
&
General population
×
300
https://t.me/medicina_free
dispersion of quantitative and qualitative responses to sympathetic
stimulation predisposes the structurally abnormal heart to
arrhythmias. Clinically, altered systemic autonomic balance is
manifested as a loss of the normal diurnal variation of heart
rate variability, which is considered a marker for risk of SCA
among MI and SCA survivors.
40
Drug Toxicity. Drug toxicity as a cause of SCA has been
documented in connection with a variety of both cardiac (antiarrhythmic) and noncardiac drugs, particularly those resulting in
QT prolongation (e.g., psychotropic drugs and antibiotics, such
as erythromycin and fluoroquinolones). However, a variety of
electrophysiologic mechanisms are operative in the genesis of
lethal ventricular tachyarrhythmias induced by various drugs.
There may be concurrent structural and functional abnormalities
that act in concert to initiate a potentially fatal arrhythmia. Combination of drugs and toxins may also predispose an individual
to SCA. Recent reports have demonstrated an increased risk
of SCA with concomitant use of cocaine and alcohol, possibly as a result of the generation of a cardiotoxic metabolite,
cocaethylene.
41
ETIOLOGIES
To predict SCA, it is important to recognize the conditions
described in greater detail later that can potentially lead to abrupt
cessation of cardiac output. Fig. 23.2 shows data derived from
various studies demonstrating the predominant pathologic
substrates of SCD. The relative risk of SCD is dependent on the
underlying substrate and is graphically demonstrated for various
populations in Fig. 23.3. These substrates are outlined in greater
detail later.
Coronary Artery Disease
CAD is the most common underlying substrate in SCD events,
accounting for 60% to 75% of all cases.
of a coronary event is more common in men than women as
3,11,12
SCD in the setting
well as in African Americans than whites. The majority (40%
to 75%) of SCA events attributed to CAD occur in individuals
with evidence of a prior MI; however, approximately 15% of SCA
victims initially present during a new ST elevation myocardial
infarction (STEMI).13 Many of the risk factors for CAD are also
predictors for SCA, including, but not limited to, hypertension, diabetes, smoking, obesity, and left bundle branch block
on ECG.
2
Nonatherosclerotic Coronary Artery Disease
Nonatherosclerotic CAD also poses a significant risk for
SCA, especially in the younger population. Common nonatherosclerotic coronary artery abnormalities include congenital
anomalies, embolism, vasculitis, myocardial bridging, vasospasm,
and dissection.
3%
7%
CM
10%
Valvular
13%
67%
Fig. 23.2 Prevalence of underlying heart disease in adult patients
who have experienced sudden cardiac death, based on data
derived from several studies.
are coronary artery disease (CAD), cardiomyopathies (CM), valvular
and hypertensive heart disease (HHD), and inheritable arrhythmia
syndromes. LQTS, Long QT syndrome; SVT, supraventricular
tachycardia. (Modified from Deshpande S, Vora A, Axtell K, Akhtar
M. Sudden cardiac death. In Brown DL, editor. Cardiac Intensive
Care. Philadelphia: Saunders, 1998, 391–404.)
9,198–202
The predominant substrates
HHD
LQTS
SVT
Others
Fig. 23.3 The incidence and number of patients with sudden cardiac death (SCD) in various
subgroups of patients. Left, SCD incidence percent per year in each subgroup. Right, Total
number of SCDs per year (n × 1000). CAD, Coronary artery disease; EF, ejection fraction; MI,
myocardial infarction; SCA, sudden cardiac arrest; VT/VF, ventricular tachycardia/ventricular fibrillation. (Modified from Myerburg RJ, Kessler KM, Castellanos A. Sudden cardiac death: structure,
function and time-dependence of risk. Circulation. 1992;85[Suppl I]:I-2–I-10.)
High CAD risk
History of CAD
EF < 30%
History of SCA
Post MI VT/VF
05
10
15 20 25 30 35 050100
SCD incidence (%/year)
150 200250
Total SCD / year
1000
228 PART IV Noncoronary Diseases: Diagnosis and Management
https://t.me/medicina_free
Coronary Artery Anomalies. Although hemodynamically
significant coronary artery anomalies are uncommon (prevalence
ranging from 0.21% to 5.79%),42 they are the second most
common cause of SCD in young adults.43 The anomaly most
commonly associated with SCD occurs when an anomalous
coronary artery originates from the opposite sinus of Valsalva
and the course of the artery traverses between the aorta and the
pulmonary trunk. However, other coronary artery anomalies
with an interarterial course as well as variants of coronary artery
anatomy (e.g., hypoplastic right coronary or anomalous origin
from pulmonary trunk) have also been implicated in SCD.44
SCD events that occur in individuals with this anomaly typically
occur during or shortly after vigorous exercise, with the proposed
mechanism entailing compression of an acutely angulated
proximal coronary artery (possibly with a slit-like ostium) and/
or compression of the left main as it courses against the root of
the pulmonary trunk during exercise when the great vessels dilate,
compromising coronary blood flow, resulting in myocardial
ischemia.45 Antemortem diagnosis of this coronary artery anomaly
is rare despite a significant number of patients experiencing
prodromal symptoms (e.g., syncope, exertional chest pain). The
index of suspicion for a coronary artery anomaly in patients,
especially athletes who present with exertional syncope, needs
to be high so that the diagnosis can be made with appropriate
diagnostic imaging, such as a cardiac computed tomography
(CT) scan that can identify not only the origin of the artery but
also its course.
Vasculitis. During the acute phase of Kawasaki disease, coronary
artery aneurysms and ectasia develop in 10% to 25% of patients.46
In later years, shrinkage of the aneurysm, intimal proliferation,
and coronary calcification contribute to stenosis, which may
result in SCD from cardiac arrhythmia and acute MI.47 Other
vasculitides, such as polyarteritis nodosa48 and syphilitic aortitis,49
can affect the coronary circulation and SCA may be a rare sequelae.
Myocardial Bridging. Myocardial bridging is a rare (0.5% to
4.5% of the general population) congenital variant in which
a segment of an epicardial coronary artery traverses through
the myocardium during a portion of its course, with a typically affected region being the mid-portion of the left anterior
descending coronary artery.50 During exertion, a critical degree
of systolic compression on the tunneled segment may occur,
resulting in myocardial ischemia. SCA has been reported to occur,
especially during exertion, in patients with severe myocardial
bridging.
51
Coronary Artery Spasm. Coronary artery vasospasm is a sudden
narrowing of the coronary artery caused by the contraction of
smooth muscle tissue in the vessel wall. Coronary artery spasm
can occasionally trigger ventricular arrhythmias and culminate
in SCA, possibly as a result of abrupt reperfusion after a period
of ischemia.
cocaine abuse.
52,53
Vasospastic angina may also occur as a result of
41
Coronary Artery Dissection. Another rare cause of acute coro-
nary syndrome and, potentially, SCA is a spontaneous dissection
of the coronary arteries that results from separation of the media
layer of the artery wall by hemorrhage with or without an
associated intimal tear.54 Coronary artery dissection is associated
with a variety of conditions, including Marfan syndrome,55 the
peripartum period of pregnancy,56 coronary involvement with
any type I aortic dissection from other causes, or a rupture of
the sinus of Valsalva aneurysm involving the coronary ostia, all
of which can potentially cause SCA.
57
Myocardial Disease
Hypertrophic Cardiomyopathy. Despite a relatively low incidence
in the general population, HCM is the most common cause of
SCD in young adults and the second largest cause of SCD overall,58
with an annual mortality rate ranging from less than 1% in
asymptomatic patients to 6% in patients with multiple risk
59,60
factors.
HCM declines with age.61 HCM is inherited as an autosomaldominant condition. Patients with HCM have asymmetric, diffuse
LV hypertrophy without compensatory dilatation of the LV
chamber and in the absence of any known cardiac or systemic
cause. On histologic examination, there is gross disorganization
of muscle bundles and myofibrillar architecture, altered gap
junctions, increased basal membrane thickness, and interstitial
fibrosis.62 These microscopic abnormalities manifest in patients
as both electrical instability and myocardial hypertrophy with
altered hemodynamics.
ventricular arrhythmias arising within the hypertrophied LV,
syncope from abrupt hemodynamic deterioration with LV outflow
tract obstruction, and ischemia, most commonly manifested as
VT/VF.
interplay of electrophysiologic and hemodynamic abnormalities,
primarily from electrophysiologic derangement of hypertrophied
and heterogeneous muscle.
HCM patients; thus, it is implicated as the substrate explaining
lethal arrhythmias in young adults or athletes. Major risk factors
for SCD include LV maximum wall thickness greater than or
equal to 30 mm, previous episode of SCA, left ventricular outflow
tract gradient of 30 mm Hg or greater at rest or 50 mm Hg or
greater with provocation, nonsustained VT, and inducible VT
at EP study.58 Additional incremental risk factors include young
age, LV dilatation with depressed EF, presence of fibrosis (delayed
enhancement on cardiac magnetic resonance imaging), and
reduced functional flow reserve.
hypertension or owing to valvular or congenital heart disease is
also associated with an increased risk for SCA.69 The risk is
proportionate to the level of severity of the hypertrophy.
Nonischemic Dilated Cardiomyopathy. Nonischemic dilated
cardiomyopathy (NIDCM) is defined by the presence of LV or
biventricular dilatation and impaired systolic function in the
absence of any ischemia or abnormal loading conditions. Primary
causes include familial cardiomyopathies, myocardial injuries
from infections, autoimmune disorders, metabolic conditions,
or exposure to toxins (e.g., alcohol, chemotherapy, heavy metals,
Unlike most other heart diseases, the risk of SCA in
Possible mechanisms for SCA in HCM include malignant
63–66
The genesis of these arrhythmias is found in a complex
SCA may often be the first manifestation of heart disease in
63,67,68
Ventricular hypertrophy secondary to systemic or pulmonary
70
CHAPTER 23 Sudden Cardiac Death 229
IV1V
https://t.me/medicina_free
or other drugs).71 In many patients with NIDCM, no causative
agent is identified; thus, the cause is labeled as idiopathic. Genetic
mutations are identified in up to 40% of patients with no other
identifiable etiology, with mutations in genes encoding titin
(TTN), myosin heavy chain (MYH7), sarcomere of cardiac
troponin T (TNNT2), and lamin A/C (LMNA) among the most
commonly reported.
9
A phenotypically distinct form of NIDCM is defined by
noncompaction of the ventricular myocardium (NVM) and is
presumed to be caused by the arrest of normal embryogenesis
of the endocardium and myocardium. Three major clinical
manifestations include heart failure, embolic events, and arrhythmias.72 Both atrial and ventricular tachyarrhythmias have been
observed with VT in 47% of patients. SCD accounted for 50%
of deaths in some reported series of NVM patients.
73,74
Overall survival is poor following a clinical diagnosis of
NIDCM: approximately 70% survival at 1 year and 50% survival
at 2 years, with the majority of deaths being sudden in nature.75
NIDCM is responsible for 10% of all adult SCD cases76 and SCD
can be the initial presentation of NIDCM. Risk factors for SCD
in the setting of NIDCM include reduced left ventricular ejection
fraction (EF), prior sustained VT, syncope, symptomatic heart
failure, and family history of SCD. Syncope is a poor prognostic
factor and is associated with a 44% incidence of SCD in 4-year
77
Ventricular tachyarrhythmias78 are the most common
mode of death, but bradyarrhythmias79 also occur, especially in
patients with severe LV dysfunction. The arrhythmia most commonly implicated in SCA is primary polymorphic VT or VF.
Furthermore, rapidly sustained monomorphic VT, in some cases
resulting from bundle branch reentry, has been observed.38 The
recognition of bundle branch reentry is critical because these
patients can be successfully cured by catheter ablation of the
right bundle branch.38 Monomorphic VT, unrelated to bundle
branch reentry, is likely associated with the presence of smaller
reentrant circuits within the myocardium. In most instances,
the triggering mechanism for the onset of primary polymorphic
VT or VF is unclear. In some cases, triggers such as electrolyte
abnormalities or the use of antiarrhythmic medications are more
easily identifiable.
Arrhythmogenic Right Ventricular Cardiomyopathy. ARVC is
an inherited cardiomyopathy with the characteristic histologic
appearance of transmural loss of right ventricular (RV) myocytes
with replacement by adipose and fibrous tissue. The hallmark
on ECG is the presence of epsilon (ε) waves, although inverted
T waves, notched S wave, and widening of QRS (>110 ms) in
the right precordial leads have also been observed (Fig. 23.4).80
Often, the signal-averaged ECG is markedly abnormal, with
late potentials being commonly seen in ARVC.81 Diagnostic
findings on imaging include regional RV akinesia, dyskinesia,
or aneurysmal dilatation on echocardiography or cardiac
magnetic resonance (CMR) imaging. Intramyocardial fat, RV
wall thinning, and delayed enhancement on CMR imaging are
complementary radiologic findings but are no longer considered
diagnostic.
82
The estimated prevalence of ARVC is 1 in 2000 to 5000 and
it is typically inherited in an autosomal dominant fashion,
although due to incomplete penetrance the disease occurs in
only 30% to 50% of offspring. Multiple genetic mutations have
been discovered that result in ARVC, with more than 60% of
mutations occurring in genes encoding desmosomal proteins
(e.g., plakoglobin, plakophilin 2, desmoglein 2, desmocollin 2,
and desmoplakin), which anchor intermediate filaments to the
cytoplasmic membrane in adjoining cells in the gap junction.
83
aVR
aVLII V2 V5
aVFIII
II
Fig. 23.4 Electrocardiograph morphology of arrhythmogenic right ventricular dysplasia with inverted
T waves, ε waves, notched S wave, and widening of QRS (>
(V1–V3). (From Nasir K, Bomma C, Tandri H, et al. Electrocardiographic features of arrhythmogenic
right ventricular dysplasia/cardiomyopathy according to disease severity: a need to broaden
diagnostic criteria. Circulation. 2004;110:1527–1534.)
V3 V6
Epsilon
wave
4
Prolonged S
wave upstroke
110 ms) in the right precordial leads
T wave inversions
until V5
230 PART IV Noncoronary Diseases: Diagnosis and Management
https://t.me/medicina_free
Patients are generally asymptomatic; unexplained syncope or
SCD may be the initial clinical manifestation, with SCD being
the first arrhythmic event in up to 50% of cases.84 In ARVC
patients treated with an ICD, the annual rate of death or VF
ranges from 1.5% to 4% in observational studies. Predictors of
delivery of ICD therapy include prior SCA or hemodynamically
significant VT, younger age, LV involvement, unexplained syncope,
presence of nonsustained VT, and VT induced during an electrophysiologic study (EPS).
85,86
Valvular Heart Disease. Disease of the heart valves poses an
increased risk for future SCA, usually as a result of LV dilatation
and/or hypertrophy. In 1% and 5% of victims of SCD, the cause
of death is attributed to valvular heart disease.
5,6
Rheumatic
valvular heart disease can, in rare cases, result in SCD due to
arrhythmias, ball valve thrombosis in the left atrium obstructing
the mitral orifice, embolization to the coronary arteries, or acute
low output circulatory failure. In aortic stenosis (AS), hypertension
and low cardiac output in the setting of LVH provoke coronary
hypotension and contribute to VT that leads to SCD.87 Prior to
aortic valve replacement (AVR), asymptomatic patients with
severe AS have an annual SCD rate of 13%.
88,89
However, this
risk is not completely mitigated by surgery, as SCD is one of the
most common modes of death in AS patients after AVR (especially
within the first 2 years), primarily attributable to arrhythmias
and thromboembolism.90 Although mitral valve prolapse (MVP)
is often described as a risk factor for SCD, there is no well-defined
mechanism for MVP causing SCD. While MVP is typically benign,
certain characteristics—such as leaflet thickness, redundancy,
fibrosis of the papillary muscles and inferobasal wall, and LV
dilation—are associated with increased ventricular tachyarrhythmias.
this may not contribute to SCD risk.
91,92
Although VT is associated with these characteristics,
93
Inflammatory and Infiltrative Disorders. Inflammatory dis-
orders, such as myocarditis, are an important cause of SCD in
the young. Myocarditis can be acute or chronic and is defined
by inflammation of the myocardium that has an infectious
origin (e.g., viral, bacterial, or parasitic infections). Patients are
typically asymptomatic and SCD (resulting from either lethal
ventricular arrhythmias or damage to the specialized conduction system) can be the only presenting sign in up to 12% of
adult myocarditis patients.
94
Initially, there is direct myocardial
injury producing edema, necrosis, and contractile dysfunction.
Scarring after the acute myocarditis has resolved may contribute
to SCA.
Noninfectious inflammatory conditions—such as collagen
vascular diseases, progressive systemic sclerosis, and granulomatous disorders (i.e., sarcoidosis)—can also cause SCA.95 Cardiac
sarcoidosis is defined by the development of sarcoid granulomas
in the heart muscle that can affect the conduction system, causing
complete heart block; create granulomatous scar, contributing
to the development of macro-reentrant ventricular arrhythmias;
or impair myocardial contractility, resulting in heart failure.
96,97
Patients with cardiac sarcoidosis are at risk for SCD and limited
data are available to aid in risk stratification. ICDs are generally
indicated when the patient has experienced sustained VT or
survived SCA; when the EF remains less than or equal to 35%
despite optimal medical therapy and immunosuppression; and
when the patient has an indication for a permanent pacemaker,
unexplained syncope presumed to be arrhythmic in etiology, or
sustained VT induced at EP study.96 Compared to other patients
with NIDCM, patients with cardiac sarcoidosis appear to receive
more frequent appropriate ICD therapies.
98,99
Infiltrative diseases, such as hemochromatosis and amyloidosis,
also can increase a patient’s risk of SCA. Amyloidosis cardiomyopathy results from the deposition of amyloid protein in
the myocardial interstitium, ultimately contributing to diffuse
myocardial thickening with impaired ventricular contractility
and/or diastolic dysfunction with restrictive physiology.
setting of cardiac amyloidosis, SCD can result from pump failure
owing to progressive diastolic and subsequent systolic biventricular
dysfunction, ventricular tachyarrhythmias, or embolization of
intracardial thrombus.
101,102
Prognosis for patients with cardiac
amyloidosis in the presence of symptomatic heart failure is
extremely poor, with a median survival of approximately 4 to 6
months.
100
In cardiac amyloidosis patients with ICDs, appropriate
ICD therapies for ventricular arrhythmias are common (27%
in one series).
103
Congenital Heart Disease. SCD is a major cause of mortality
in adults with congenital heart disease (ACHD), affecting 7%
to 19% of the population.
37,104
The underlying cardiac lesions
can be mild but the majority of cases involve complex congenital
heart disease. Arrhythmias are the most common cause of SCD
in the ACHD population; aortic dissection, cerebrovascular
accident, pulmonary embolus/hemorrhage and MI also contribute
to SCD in this population, however. Factors that were associated
with SCD in adults with congenital heart disease include supraventricular tachycardia (SVT), moderate to severe dysfunction
of the systemic ventricle, and increased QRS duration.
Various congenital lesions have been associated with SCA.
Congenital aortic stenosis
105
can predispose to SCA. The risk for
SCA correlates with the severity of the stenosis; AVR does not
eliminate the risk but has been shown to reduce it. Both cyanotic
and noncyanotic Eisenmenger syndrome
106
can predispose to
SCA. Patients who have undergone surgical procedures for
correction of transposition of the great arteries (TGA) may be
at increased risk for SCA resulting from bradycardia (e.g., sick
sinus syndrome) and tachycardias (e.g., atrial flutter).
standing right ventricular strain, abnormal electrophysiologic
architecture secondary to general and physical stress, and sequelae
of the surgical corrective procedure all contribute to the increased
risk of SCD in TGA patients.
108
The incidence of late SCD is
approximately 50% but has been reduced with the arterial switch
operation.
107
Up to 5% of patients with surgically repaired
tetralogy of Fallot (ToF) may experience potentially fatal arrhythmias as a late complication. Some of the risk factors in adults
with ToF include LV systolic or diastolic dysfunction, nonsustained
VT, QRS duration greater than 180 ms, extensive RV scarring
(particularly in the right ventricular outflow tract [RVOT]) or
inducible sustained VT at EP study. The mechanism for sustained
monomorphic VT in ACHD patients is generally macro-reentrant
with a critical isthmus located within an extensively scarred RVOT
100
104
107
Long-
In the
Соседние файлы в папке Библиотека им академика М.И. Перельмана