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346 PART IV Noncoronary Diseases: Diagnosis and Management
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BOX 33.2 CHD-Related Etiologies of
Myocardial Ischemia
1. Anomalous left coronary artery arising from a pulmonary artery (ALCAPA)
with late presentation or with complications resulting after repair in infancy
2.
A left coronary artery arising from the right sinus of Valsalva or the right
coronary artery arising from the left sinus of Valsalva when these malformations are associated with an interarterial course between the aorta and the
pulmonary artery
3.
Coronary arteries transposed in the arterial switch operation for transposition
of the great vessels, with subsequent compromise
4.
Coronary aneurysm, with congenital or inflammatory etiology, such as
Kawasaki disease or panarteritis nodosa with associated thrombosis
5. Coronary artery compressed by myocardial muscle bridge
6. Coronary arteriovenous or coronary-cameral fistula
7. Aortic stenosis with myocardial ischemia or pulmonary stenosis with right
ventricular ischemia
Prior to surgical repair, when the entire coronary circulation is
dependent on the right coronary artery and collaterals, patients
can develop progressive ischemia with growth, resulting in angina
or heart failure. If there are symptoms or signs consistent with
myocardial ischemia, the patient should have an assessment of
ventricular function by echocardiography or radionuclide scanning
and some measure of myocardial viability by positron emission
tomography, dobutamine echocardiography, or resting thallium-201
scanning. If ischemic myocardium is found, then revascularization
should be performed.
An uncommon condition causing myocardial ischemia is the
left coronary artery arising from the right sinus of Valsalva. This
lesion may not, and probably usually does not, cause myocardial
ischemia in most patients. However, in some patients, sudden
and usually transient occlusion of the left coronary artery can
occur; the typical setting is in a young adult during or just after
exercise. This causes profound ischemia of the LV and is usually
manifested by sudden death or syncope and, occasionally, by
profound angina, with or without MI. The reason for the sudden
ischemic episode is not known. The usual course of such a vessel
is obliquely posterior, between the RV outflow tract and the
aortic root. This could result in a kinking or compression of the
artery during exercise, or possibly in collapse of the orifice of
the coronary ostium. However, coronary spasm cannot be ruled
out. This type of event may occur after a long history of
asymptomatic exercise and with inability to precipitate ischemia
with similar exercise after the event.
Less commonly, the right coronary artery arises from the left
sinus of Valsalva and causes sudden death, syncope, or inferior
MI. This is less often a cause of sudden death because sudden
occlusion of the right coronary artery generally leads to inferior
MI that is more likely to be hemodynamically tolerated.
Any patient under age 30 years who has presyncope or syncope
during exercise or a life-threatening ventricular arrhythmia with
an apparently normal heart on ECG should be suspected of
having an anomalous origin of the left or right coronary artery
from the opposite sinus of Valsalva.
20
Coronary CT or MRI is
the recommended imaging modality to define coronary course
in this patient group.21 Definitive identification with invasive
18
catheterization may be required. If such an anomaly is identified,
bypass grafting should be considered.
HEART FAILURE IN THE ADULT WITH
CONGENITAL HEART DISEASE
The underlying mechanisms for the development of congestive
heart failure in the setting of congenital heart disease are similar
to those in acquired disease. The causes of congestive heart failure
are as follows:
1. Primary pump failure involving either the RV or LV
2. Ventricular hypertrophy and fibrosis leading to diastolic
dysfunction
3. Mechanical dysfunction, usually on the basis of valvular disease
or failure of a palliative procedure
The onset of heart failure in adults with congenital heart
disease is generally gradual; thus, patients usually have chronic
or subacute symptoms. Acute presentations are most common
in those with sudden valvular incompetence, ischemia (discussed
previously), new onset of arrhythmia, or sudden exacerbations of
chronic congestive heart failure. Identifying the cause of congestive
heart failure in these patients requires an accurate and detailed
clinical history and physical examination, a systematic noninvasive
evaluation and, frequently, a referral for an invasive hemodynamic
evaluation when information remains incomplete.
The clinical history is essential in diagnosing the cause of heart
failure in adults with congenital heart disease. Critically important
are knowledge of the primary lesion and the presence of associated
lesions. One example is coexistence of a bicuspid aortic valve that
becomes clinically manifest with stenosis or insufficiency many years
following a repair for aortic coarctation. Second, the timing and
nature of both palliative procedures and surgical repairs strongly
influence late manifestations. Often, a palliative procedure may result
in late complications; for example, congenital aortic stenosis treated
with surgical valvotomy or balloon valvuloplasty may have recurrent
stenosis or progressive aortic regurgitation. Third, the specific
procedure performed to achieve the primary repair influences late
outcome; for example, a patch placed across the pulmonary annulus
(i.e., transannular) to alleviate pulmonary stenosis in teratology of
Fallot is associated with progressive pulmonary insufficiency, whereas
other procedures, such as RV-to-PA conduit placement, are more
likely to be associated with residual stenosis. Finally, the development
of acquired disease may influence the natural history of congenital
heart disease, such as accelerated atherosclerotic coronary disease
in patients with coarctation of the aorta.
The physical examination should be directed toward identify-
ing signs of systemic venous congestion (e.g., elevated jugular
venous pressure, leg edema, ascites, pleural effusion) and pulmonary venous congestion (e.g., pulmonary rales). Evidence of
ventricular enlargement will be evident on precordial palpation,
but the RV and LV may be transposed. Murmurs of valvular
stenosis and insufficiency should be carefully noted. Findings
of peripheral cyanosis or clubbing in patients with palliated
single ventricles may represent the development of venovenous
collateral vessels (desaturated systemic venous blood draining
directly into the left atrium or pulmonary venous circulation).
These collaterals represent a right-to-left intrapulmonary shunt
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and may cause both hypoxemia and ventricular dysfunction
due to chronic volume overload. Hypoxia should also increase
suspicion of a pleural effusion or a thromboembolic event in
patients with a Fontan circuit, who are more prone to these
complications. The absence of a continuous murmur in a
patient with a Blalock-Taussig shunt may indicate obstruction
or pulmonary vascular disease and explain worsening cyanosis.
The approach to noninvasive diagnosis of heart failure in the
adult with congenital heart disease is similar to that for patients
with acquired disease, except that knowledge of the anatomy
unique to the primary congenital lesion and to surgical repairs
is required. Inspection of the ECG for conduction defects and
arrhythmias occasionally reveals the cause of heart failure.
Echocardiography should be considered early in the presentation
of these individuals, with the specific goals as follows:
1. Establishing or confirming the primary and secondary
diagnoses
2. Establishing the adequacy of prior surgical repairs, including
patch competency and shunt patency
3. Evaluating ventricular systolic and diastolic function
4. Identifying hemodynamically significant valvular dysfunction,
either native or prosthetic, and intracardiac shunts
TEE may be superior to transthoracic imaging, especially in
evaluation of the atria, interatrial septum, conduits, and prosthetic
valves. Although it is a semi-invasive procedure, TEE has been
proven safe in critically ill patients once respiratory status is
stabilized. Cardiac magnetic resonance imaging (MRI) and
computed tomography (CT) may be helpful as well, providing
both a cardiac assessment and helping delineate extracardiac
pulmonary anatomy. However, both procedures may be impractical in unstable patients.
When the clinical and noninvasive data are inconclusive,
cardiac catheterization may be necessary. It is important that
the goals of the study be predetermined and that the catheterization be performed by personnel familiar with congenital heart
disease. Incomplete information can lead to inappropriate
treatment.
Etiologies of Pump Failure
There are several causes of pump failure unique to the population
of adults with congenital heart disease. The RV functioning in
the systemic circulation is encountered in two groups of patients:
those with congenitally corrected transposition of the great arteries
(L-transposition) and those with transposition of the great vessels
palliated with an interatrial baffle operation (i.e., Mustard or
Senning procedures). Although the systemic RV undergoes
hypertrophy and is thus able to pump against the increased
afterload for many years, late failure is a feature of the natural
history of the patient population usually presenting in the fourth
or fifth decade of life.
pulmonary congestion and occasionally low output. It is necessary
to exclude obstruction of the pulmonary venous limb of the
interatrial baffle, which may also lead to pulmonary venous
congestion and may be confused with failure of the systemic
ventricle. Likewise, systemic venous congestion may occur in
the presence of obstruction to the systemic venous limb of the
baffle. These structural lesions may require percutaneous
22
The signs and symptoms are those of
intervention or surgery. Precipitants such as incessant atrial
tachyarrhythmias should be identified, which can lead to ventricular dysfunction.
Another group of patients who are likely to develop “pump”
failure are those whose anatomy falls within the broad category
of single ventricles. These include hypoplastic left heart syndrome and patients with double-outlet RV, double-inlet LV,
tricuspid atresia, and pulmonary atresia with intact ventricular
septum. By adulthood, these patients have been treated with a
variety of palliative procedures, in most cases to increase
pulmonary blood flow, usually through a series of staged surgeries leading to a cavopulmonary connection (i.e., Fontan or
Glenn procedure), although adults may infrequently present
who have a systemic-pulmonary arterial connection (i.e., Potts
or Waterston procedure). Single-ventricle physiology patients
who underwent the Fontan procedure have improved survival
rates and are presenting with complications in adulthood with
increasing frequency, ventricular failure being one fairly inevitable complication. Failure is often multifaceted. The Fontan
circulation directly connects systemic venous return to the
pulmonary arteries, thereby creating a pumpless, portal-like
system. As such, pulmonary venous return is hindered by
pulmonary impedance, which creates a state of chronic systemic
venous congestion and compromised cardiac preload with
chronically low cardiac output.23 Impairment of any of the
components comprising the Fontan system listed here may
greatly affect the overall circuit function.
(A) The venoarterial Fontan connection itself: At risk of
obstruction by thrombus formation, rising systemic
venous pressures and increasing coronary sinus pressures
causing decreased coronary perfusion pressures
(B) Pulmonary arteries: Often prone to recurrent stenosis
and related to the underlying congenital defect or
thromboembolic obstruction
(C) Pulmonary capillary network: Resistance being the primary
modulator of cardiac output with resultant compromise
from any elevation in pressure
(D) Pulmonary veins: May be at risk of obstruction over time
owing to an enlarging atrium with septal shift
(E) Atrioventricular valvar function: Regurgitation being a
main risk factor for late mortality
24
(F) Systemic ventricular function
Other potential causes of late systolic failure seen in ACHD
patients include lesions that lead to chronic volume overload of
the systemic ventricle. Included in this group are unrepaired
shunts—such as ASD, VSD, or a PDA—and congenital causes
of aortic and AV valve regurgitation (mitral in the systemic LV
and tricuspid in the systemic RV). Congenital defects leading to
pressure-overloaded ventricles also contribute to etiologies of
systolic heart failure presenting in adulthood, such as residual
LV or RV outflow tract obstruction, aortic or pulmonic valve
stenosis, or coarctation of the aorta.
Abnormalities of Diastolic Function
Diastolic dysfunction as the cause of RV or LV failure is less
common in patients with congenital heart disease than in those
with acquired heart disease, but its incidence will increase as
348 PART IV Noncoronary Diseases: Diagnosis and Management
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congenital patients continue to age. Symptoms of pulmonary
congestion may occur in the setting of LV hypertrophy and fibrosis
due to long-standing LV outflow tract obstruction, congenital
valvular aortic stenosis, or aortic coarctation. Once obstruction
is relieved, the hypertrophy regresses, but fibrosis may persist,
producing late arrhythmias and even sudden death. A wellrecognized consequence of impairment in LV diastolic function
that occurs with age is increased left-to-right shunting across
an ASD. The increased shunting may contribute to the almost
ubiquitous atrial arrhythmias in patients older than 60 years
with ASD and ultimately RV failure from volume overload.
RV hypertrophy is most common in the setting of pulmonary
valve stenosis. The overwhelming success of surgical and balloon
valvuloplasty for this condition in childhood has resulted in
normal survival. Patients with repaired tetralogy of Fallot
demonstrate LV and RV fibrosis by late gadolinium enhancement
on MRI that correlates with ventricular dysfunction, exercise
intolerance, and arrhythmia.25 Similarly increased fibrosis after
atrial switch procedures correlates with aging, declining function,
and clinical events.
26
Abnormalities of Valve Function
The sudden development of left-sided valvular regurgitation is
most likely to present as acute heart failure. Acute aortic regurgitation associated with congenital heart disease is most likely from
destruction of a bicuspid valve owing to endocarditis or from
dissection of the aorta in Marfan syndrome. Aortic valve endocarditis may also occur in the setting of discrete fibromuscular
subaortic stenosis and may complicate a so-called supracristal
(subarterial) VSD. An acute manifestation of the latter is rare.
Acute mitral regurgitation may also occur in the setting of
endocarditis or as a result of chordal rupture in the presence of
mitral valve prolapse. Prosthetic valve dysfunction is discussed
later in this chapter.
Failed Palliative Procedures
Systemic-Pulmonary Arterial Shunts. Systemic-pulmonary
shunts (Table 33.3) are employed in cyanotic patients with severely
reduced pulmonary arterial blood flow, usually due to outflow
obstruction. The three most commonly used shunts were the
Waterston procedure, which connects the ascending aorta to the
right pulmonary artery; the Potts procedure, which connects
the descending aorta to the left pulmonary artery; and the
Blalock-Taussig shunt, which connects the subclavian artery
directly (classic) or indirectly via a Gore-Tex graft (modified)
to the pulmonary artery. The Waterston and Potts procedures
are no longer performed because they are associated with a high
incidence of congestive heart failure and pulmonary vascular
disease. Blalock-Taussig shunts are still routinely performed in
infants with complex congenital heart disease, although their
creation is nearly always followed by a more extensive palliative
or completely reparative surgery that involves take-down of the
initial shunt. Therefore, their presence in today’s ACHD population is exceedingly rare. If encountered, congestive heart failure,
endocarditis, brain abscess, and severe cyanosis due to outgrowing
of the shunt or development of pulmonary vascular disease are
potential sequelae in these patients. A continuous murmur is a
TABLE 33.3 Palliative Shunts
Anatomy Comment
Systemic Arterial–Pulmonary Arterial
Classic BT Subclavian artery to PA Absent ipsilateral radial
pulse; continuous
murmur
Modified BT Subclavian to PA conduit Preserved pulse;
continuous murmur
Central shunt Aorta to PA conduit Continuous murmur
Waterston Ascending aorta to RPA Continuous murmur
Potts Descending aorta to LPA Continuous murmur
Systemic Venous–Pulmonary Arterial
Glenn Superior vena cava to PA No murmur; arrhythmias
uncommon
Fontan Total cavopulmonary
shunt
Other
Rastelli Right ventricle to PA Valve degeneration may
a
Continuous murmur may disappear in presence of pulmonary
hypertension.
BT, Blalock-Taussig; LPA, left pulmonary artery; PA, pulmonary artery;
RPA, right pulmonary artery.
No murmur; atrial
arrhythmias common
lead to pulmonary
insufficiency murmur.
a
a
normal finding; its absence indicates obstruction of the shunt.
Thus worsening cyanosis and a diminished murmur should
prompt urgent catheterization and intervention. Endarteritis
may also complicate this type of shunt.
Cavopulmonary Connections. Cavopulmonary connections
(see Table 33.3) consist of a group of palliative procedures com-
monly performed in patients with tricuspid atresia and other
single-ventricle lesions, broadly categorized into the Glenn and
Fontan procedures. In the Glenn procedure, the superior vena
cava is anastomosed to the right pulmonary artery. However, in
older children and adults, the blood supply from the head and
neck is rarely adequate for relief of cyanosis. Thus many patients
proceed to a total cavopulmonary connection (i.e., Fontan
procedure), which is accomplished through a variety of surgical
techniques. Supplemental systemic-pulmonary arterial shunts
are also used. Pulmonary blood flow is predominantly passive;
thus systemic venous pressures are chronically elevated.
The family of Fontan procedures is associated with frequent
multiorgan complications, including chylous pleural effusions,
liver failure, protein-losing enteropathy, and pulmonary thromboembolic disease. Although they are more likely to present
chronically, these complications may occasionally result in an
acute decompensation, especially in patients with limited cardiopulmonary reserve, and may be triggered by arrhythmia or
a pulmonary thromboembolic event. In addition, increasing
pleural effusions compromise respiratory status through atelectasis, exacerbating cyanosis. Ascites from liver failure and
hypoalbuminemia may also reduce lung volumes by elevating
the diaphragm. Thrombi arising in the deep venous system and
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right atrium can result in pulmonary emboli, with a rise in
pulmonary artery pressures and consequent reduction in pulmonary blood flow. Acutely, TEE and catheterization with
angiography may be necessary to exclude conduit obstruction
and thromboembolic disease. Acute management may include
thoracentesis, paracentesis, and anticoagulation or thrombolytic
therapy.
Heart Failure Management Considerations
In general, initial management of the patient in heart failure
should be aimed at acute stabilization by reducing preload using
diuretics and nitrates, reducing afterload using vasodilators, and
providing inotropic support when necessary. However, therapies
for heart failure in the patient with congenital disease must be
tailored to the individual. For example, in patients with Eisenmenger syndrome or unrepaired tetralogy of Fallot, excessive
diuresis can result in a severe fall in cardiac output and afterload
reduction with systemic vasodilators may worsen right-to-left
shunts. Patients with outflow tract obstruction and secondary
hypertrophy are highly dependent on adequate preload and,
therefore, are subject to hypotension with diuresis. Thus, the
degree of diastolic dysfunction and obstruction necessitates
extreme caution with diuresis and avoidance of hypovolemia;
slowing of the heart rate is also necessary, when appropriate.
Prompt correction of inciting or aggravating conditions, such
as arrhythmias and fever, may benefit the patient. For patients
in atrial fibrillation or other atrial tachycardia, restoration of
sinus rhythm may significantly improve cardiac output. Once
the patient is acutely stabilized, further diagnostic procedures
can be performed to determine definitive therapy.
Heart failure management for patients with a failing systemic
RV requires some special consideration but is generally treated
in the same manner as the failing systemic LV. Treatment with
inotropic agents may be indicated acutely until adequate afterload
reduction can be instituted. The use of β-blocker therapy in the
failure of the systemic RV may be of long-term benefit by analogy
to LV failure, but only limited studies have been performed in
this patient group. The same can be said for angiotensinconverting enzyme inhibitors or angiotensin receptor blockers.
There are emerging data demonstrating hemodynamic benefit
of cardiac resynchronization therapy in patients with a systemic
RV who have evidence of refractory heart failure and ventricular
dyssynchrony, though the benefit is smaller than seen with the
systemic LV.
for heart transplantation.
The failing single-ventricle patient who has undergone either
the Glenn or Fontan palliation requires a thoughtful diagnostic
evaluation and therapeutic approach. Similar to patients with a
systemic RV, there is a paucity of large, multicenter, longitudinal
studies demonstrating benefits with traditional heart failure
medications in this patient group.28 However, these medications
continue to be frequently used. There is growing evidence
demonstrating benefit of agents such as sildenafil that reduce
pulmonary vascular resistance to augment pulmonary blood
flow, cardiac filling, and cardiac output in this patient population.29 Hence, inhaled nitric oxide could be considered in a critical
care setting in a patient with Fontan physiology who presents
27
Patients with intractable cases should be considered
with hypoxia and ventricular dysfunction of uncertain etiology.
Fontan conversion to an extracardiac conduit may be considered
for refractory atrial tachyarrhythmias thought secondary to
atriopulmonary Fontan types. When combined with a Maze
procedure, this operation may help control atrial arrhythmias.
Catheter ablation has reduced recurrence.
30
The literature regarding mechanical circulatory support use
in ACHD patients who are in heart failure is somewhat limited.
In most patients, the principles of utilization are the same as in
noncongenital patients, with some exceptions. Ventricular assist
device (VAD) placement requires additional consideration in
these patients who have already undergone prior—and sometimes
multiple—thoracotomies, which increases the surgical complexity
of placement. Extracorporeal membrane oxygenation (ECMO)
support or intraaortic balloon pump (IABP) use during postoperative care after a repeat cardiac operation in high-risk ACHD
patients has been shown in some studies to be associated with
significant inpatient mortality.31 The most challenging patients
for VAD placement are adults who have undergone the Fontan
procedure. They have severely limited options among existing
devices due to their single-ventricle anatomy and the required
decision to support either the pulmonic circulation or the systemic circulation. However, few studies have described success
with temporary use of such support as a bridge to transplant.
There are even fewer studies describing use of Impella devices
(Abiomed, Danvers, MA) for such temporary support in acute
ventricular dysfunction, and this approach may be seen with
increasing frequency until new devices exist for this unique
population.
32
Prosthetic Valve and Prosthetic Material Failure. The pre-
sentation of prosthetic valve dysfunction in adults with congenital
heart disease is generally similar to that in patients who have
had valve replacement for acquired heart disease; however, there
are several important differences in patients who had valve
replacement during childhood. First, the size of the valve may
be an important factor because growth of the patient produces
increased requirements for higher stroke volumes. Thus the
patient with prosthetic valve mismatch may have diminished
exercise tolerance and heart failure. Second, the rate of degeneration of bioprostheses or homografts is faster in young patients;
leaflet thickening and tearing may occur as early as 5 years
following implantation instead of the expected 10 to 15 years
in adult patients.
33
Third, prosthetic valves are more frequently
combined with a conduit that can also become obstructed through
a process known as pseudointimal thickening.
Other complications of prosthetic valves common in those
with acquired and congenital valve disease include endocarditis
and thrombosis; the latter is confined primarily to mechanical
prostheses. Primary failure is rare in the types of mechanical
valves (most frequently, St. Jude bileaflet valves) usually encountered in this population.34 Prosthetic materials are also used for
patch closures of ASDs and VSDs. Operations performed before
1970 were more prone to patch leaks. Although these persistent
defects are rarely hemodynamically significant, they represent
an important nidus for endocarditis at the site of the jet lesion
and are a potential cause of hemolysis.
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OTHER CATASTROPHIC EMERGENCIES
Cerebrovascular Disease
Among the neurologic complications of congenital heart disease
is subarachnoid hemorrhage as a result of rupture of an aneurysm
of the circle of Willis in association with aortic coarctation.
Although rupture is more common in those with unrepaired
coarctation, patients with repairs remain at risk, especially in
the presence of persistent hypertension. Patients with coarctation
of the aorta are also at increased risk of thrombotic strokes as
a result of long-standing hypertension.
Additional neurologic complications of congenital heart disease
include brain abscesses and embolic stroke in the presence of a
right-to-left shunt. Brain abscesses may be indicated by new
onset of seizures, headache, or unexplained fever. The diagnosis
can be made by CT or MRI. In young patients with acute cerebral
ischemia, an intracardiac communication responsible for rightto-left shunting should be suspected. Many patients have been
shown to have a patent foramen ovale by transthoracic echocardiography or TEE. An ASD may also predispose to a cerebral
ischemic stroke.
Thrombotic strokes are rare in patients with cyanotic heart
disease and secondary erythrocytosis.35 Secondary erythrocytosis
is a physiologic response to chronic hypoxia in these patients.
Prophylactic phlebotomy is not indicated in the absence of
symptoms and may, in fact, be harmful. However, the patient
with decompensated erythrocytosis (hematocrit >65%), particularly in the context of iron-deficiency anemia, may have moderate
to severe hyperviscosity symptoms—including headaches, lethargy,
and, less frequently, seizures.36 Phlebotomy is indicated in these
patients only for temporary relief of severe symptoms or preoperatively. Phlebotomy should be limited to removal of one
unit of blood at any one time in conjunction with volume
replacement with saline. Additionally, these patients benefit from
iron replacement in the event of iron-deficiency states, which
are common and often overlooked.
Pulmonary Hemorrhage
Pulmonary hemorrhage can occur in patients with Eisenmenger
syndrome as a result of pulmonary infarction and pulmonary
arteriolar rupture. These life-threatening events may complicate
pregnancy and are potentially fatal. However, the differential
diagnosis of hemoptysis includes pulmonary edema (which
may respond to diuretic therapy) and pulmonary infections.
When chest radiography is nondiagnostic, bronchoscopy may
be required.
Pulmonary artery hemorrhage may complicate right heart
catheterization with a flow-directed, balloon-tipped catheter,
especially in the presence of severe pulmonary vascular disease.
When it is necessary to perform invasive monitoring, care should
37
be taken not to inflate the balloon in a small pulmonary branch
artery but rather to inflate it in a larger branch, then float it out
to a smaller branch to obtain the pulmonary capillary wedge
pressure.
Control of hemoptysis may be thwarted by the bleeding
diathesis that accompanies the polycythemia of cyanotic heart
disease. These management issues are beyond the scope of this
chapter.
Eisenmenger Syndrome
In Eisenmenger syndrome, irreversible pulmonary vascular disease
develops in response to a left-to-right shunt (e.g., VSD, ASD,
PDA).38 There is consequent reversal of shunt flow from right
to left and cyanosis. The oxygen saturation is markedly decreased
and polycythemia is present. There is ECG and radiographic
evidence of RV hypertrophy. These patients have tenuous
hemodynamics and are susceptible to severe hypotension in the
setting of dehydration or hypovolemia from many causes, including diuretic treatment. Because of fixed pulmonary vascular
resistance, there is limited ability to increase cardiac output.
Systemic vasodilators are contraindicated because they may result
in hypotension and worsening cyanosis with increased right-to-left
shunting. Pregnancy is poorly tolerated; a high fetal and maternal
mortality is associated with Eisenmenger syndrome.39 Pulmonary
thrombosis, hemorrhage, or both may complicate pregnancy.
Endocarditis and arrhythmias are common. As mentioned
previously, brain abscess may occur in this setting. Advanced
pulmonary vasodilator therapy in this very sick cohort is showing
increasing promise as large studies demonstrate greater survival
with their use.
40
CONCLUSION
The numbers of adult patients with congenital heart disease are
increasing at a steady rate. These patients require ongoing surveillance for potential residual complications related both to the
natural history of their primary lesion and to the palliative and
reparative procedures performed. They are not likely to present
frequently to emergency departments and cardiac intensive care
units; however, appropriate treatment requires an understanding
of how the physiology of the particular congenital heart lesion
influences clinical presentation and the response to conventional
therapies. Awareness of the likely complications to expect with
common lesions coupled with a consciousness of the unique
anatomy of each individual will improve diagnostic accuracy
and help determine the best treatment plan, often based on
analogies to general cardiac care.
The full reference list for this chapter is available at
ExpertConsult.com.
CHAPTER 33 Hemodynamically Unstable Presentations 350.e1
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Dis. 2017;12(1):17–23.
13. Murphy JG, Gersh BJ, Mair DD, et al. Long-term outcome in
patients undergoing surgical repair of tetralogy of Fallot. N Engl
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14. Gatzoulis MA, Balaji S, Webber SA, et al. Risk factors for
arrhythmia and sudden death late after tetralogy of Fallot: a
mulitcentre study. Lancet. 2000;356:975–981.
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complications in tetralogy of fallot? JACC Cardiovasc Imaging.
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16. Babu-Narayan SV, Kilner PJ, Li W, et al. Ventricular fibrosis
suggested by cardiovascular magnetic resonance in adults with
repaired tetralogy of Fallot and its relationship to adverse
markers of clinical outcome. Circulation. 2006;113(3):
405–413.
17. Therrien J, Siu SC, Harris L, et al. Impact of pulmonary valve
replacement on arrhythmia propensity late after repair of
tetralogy of Fallot. Circulation. 2001;103(20):2489–2494.
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the American College of Cardiology/American Heart Association
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33. Laks H, Marello D, Drinkwater DC, et al. Prosthetic materials:
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OUTLINE
https://t.me/medicina_free
Calcium Channel Antagonists, 352
Pharmacology, 352
Pathophysiology, 352
Clinical Manifestations, 352
Management, 353
β-Adrenergic Antagonists, 354
Pharmacology, 354
Pathophysiology, 354
Clinical Manifestations, 354
Management, 354
Digoxin, 355
Pharmacology, 355
Pathophysiology, 355
Clinical Manifestations, 355
Management, 355
Sodium Channel Blocking Agents, 356
Pathophysiology, 356
Pharmacology and Clinical
Manifestations, 356
Class Ia Antidysrhythmics, 356
Class Ib Antidysrhythmics, 358
Class Ic Antidysrhythmics, 358
Class III Antidysrhythmics, 358
34
Overdose of Cardiotoxic Drugs
Richard Koch,* Christie Sun, Alicia Minns, Richard F. Clark
Cyclic Antidepressants, 359
Pharmacology, 359
Pathophysiology, 359
Antipsychotics (Phenothiazines, Butyrophenones, and
Atypical Agents), 360
Antihistamines, 360
Management of Sodium Channel Blocking Drug
Toxicity, 361
Illicit Drugs, 362
Cocaine, 362
Pharmacology, 362
Pathophysiology, 363
Clinical Manifestations, 363
Novel Psychoactive Substances, 364
Pharmacology, 364
Pathophysiology, 364
Clinical Manifestations, 364
Synthetic Cannabinoids, 365
Pharmacology, 365
Pathophysiology, 365
Clinical Manifestations, 365
Management, 365
Conclusion, 366
Cardiac arrhythmias, myocardial depression, and vasodilation
are the major cardiovascular effects observed in poisonings. A
large number of therapeutic and nontherapeutic agents can cause
toxicity directed toward the cardiovascular system, whether in
the setting of an actual overdose or merely a therapeutic misadventure. This chapter addresses some of the most significant
and most common cardiovascular toxins. These toxicants are
briefly described, including a review of relevant pharmacology,
known pathophysiology, clinical manifestations of poisoning,
and current management recommendations. In all such cases,
consultation with a medical toxicologist or a certified regional
poison control center should be considered.
*The views expressed in this article are those of the author and do not
necessarily reflect the official policy or position of the Department of
the Navy, Department of Defense, or the United States Government.
This chapter begins with a review of poisoning due to
calcium channel antagonists and β-adrenergic receptor
antagonists (β-blockers). These two primary cardiovascular
drug classes account for well over half of the life-threatening
events and deaths due to cardiovascular agents reported to the
American Association of Poison Control Centers each year.
Digitalis poisoning is also discussed. Finally, agents that produce
cardiotoxicity primarily through sodium channel blockade
and those with prominent sympathomimetic toxicity are
reviewed.
Not included in this chapter are a number of other cardiotoxic
agents that are less commonly encountered or that demonstrate
unique mechanisms of toxicity that are beyond the scope of this
general discussion. The reader is referred elsewhere for review
of these agents, which include clonidine and other antihypertensive agents, antidysrhythmics not noted earlier, cyclosporine,
1
351
CHAPTER 34 Overdose of Cardiotoxic Drugs 351.e1
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Keywords
cardiotoxicity
poisoning
overdose
dysrhythmia
352 PART IV Noncoronary Diseases: Diagnosis and Management
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colchicine, chemotherapeutic agents (doxorubicin; anthracyclines
such as daunorubicin and idarubicin), and certain metals
(selenium, cobalt, copper, and arsenic).
CALCIUM CHANNEL ANTAGONISTS
Pharmacology
The calcium channel blocking drugs (CCBs) are a heterogeneous class of drugs that block the movement of calcium from
extracellular sites through “slow channels” into cells.2 There
are two major categories of these agents: nondihydropyridines, which include phenylalkylamines (e.g., verapamil) and
benzothiazapines (e.g., diltiazem); and dihydropyridines (e.g.,
nifedipine, amlodipine, nicardipine, nimodipine). They are
used in a variety of disease states and clinical settings, including
coronary vasospasm, supraventricular arrhythmias, hypertension,
migraine headache, Raynaud phenomenon, and subarachnoid
hemorrhage.3 In general, CCBs are rapidly absorbed from the
gastrointestinal tract and, while the majority undergo extensive
first-pass hepatic metabolism yielding low systemic bioavailability,
taken in overdose, hepatic enzymes are saturated, reducing the
first-pass effect.4 The volume of distribution of these agents is
large, except for nifedipine, and protein binding is high (>90%
for all but diltiazem). Additionally, interactions through CYP3A4
or inhibition of P-glycoprotein–mediated drug transport may
change clearance or bioavailability.
not affect clearance of CCBs with the exception of a somewhat
pharmacologically active metabolite of verapamil that is renally
excreted.8 Terminal half-lives are generally from 3 to 10 hours,
but all three classes of CCBs are available in sustained-release
preparations, which can result in greatly prolonged half-lives
and clinical effects.
Pathophysiology
CCBs can exert profound effects on the cardiovascular system,
particularly in overdose. They work by antagonizing L-type or
long-acting voltage-gated ion channels in the cardiac pacemaker
cells and decreasing phase 2 calcium ion flux in smooth muscle
cells of blood vessels. Sinus node depression, impaired atrioventricular (AV) conduction, depressed myocardial contractility, and
peripheral vasodilation may result.
Electrophysiologic effects are most prominent with nondihydropyridines and are seen much less often with the dihydropyridines, which work primarily on peripheral vasculature. Sinus
node function may be significantly altered by nondihydropyridines
in patients with underlying sinus node disease; in excess, these
agents may prolong AV nodal conduction sufficient to produce
high-grade heart block. The effect of decreased myocardial
contractility is most pronounced in overdose or in patients who
already have depressed myocardial function from underlying
disease or concomitant drugs. Contraction of vascular smooth
muscle, particularly arterial, can also be affected by CCBs through
inhibition of calcium influx. In overdose, the effect of vasodilation
on systemic blood pressure may be profound. However, in some
cases, especially those involving the dihydropyridines, vasodilation
may be ameliorated by a reflex increase in sympathetic activity,
with increased heart rate and cardiac output.
4–7
Impaired renal function does
BOX 34.1 Clinical Features of Calcium
Antagonist and β-Blocker Overdose
Cardiovascular
Hypotension, shock
Dysrhythmias
Sinus bradycardia
Second- and third-degree atrioventricular block with nodal or ventricular
escape
Sinus arrest with atrioventricular nodal escape
Asystole
Prolonged QRS, ventricular ectopy/tachycardia (propranolol)
Hypertension, tachycardia (pindolol)
Central Nervous System
Lethargy, confusion, coma
Respiratory arrest
Seizures (especially from propranolol)
Gastrointestinal
Nausea, vomiting
Metabolic
Hyperglycemia (verapamil, diltiazem)
Lactic acidosis
Clinical Manifestations
The most serious consequences of calcium antagonist toxicity
result from the pharmacodynamic effects of the specific agent
on the cardiovascular system, although unique features of the
different agents’ specificity profiles may be lost in overdose.9
Clinical features are summarized in Box 34.1. Bradycardia and
conduction defects are among the most frequent electrocardiogram (ECG) findings in overdose of the nondihydropyridines.
Additionally, hypotension is present in most significant exposures
to any CCB. These features generally develop within 1 to 2 hours
of exposure, but the onset of moderate to severe cardiovascular
manifestations may be delayed for more than 12 hours when a
sustained-release preparation has been ingested.
Patients at particular risk for toxicity from calcium antagonists
include those with sinus node dysfunction, AV nodal conduction
disease, severe myocardial dysfunction, obstructive valvular
disease, hypertrophic cardiomyopathy, hepatic failure (leading
to impaired elimination), and concomitant use of β-blockers or
digoxin.11 In addition, verapamil may dangerously accelerate
conduction through accessory pathways when administered
intravenously to patients with accessory or anomalous AV connections, such as in Wolff-Parkinson-White syndrome.12 It should
not be given to patients with atrial fibrillation and evidence of
preexcitation on ECG.
Profound hypotension is the major manifestation of overdose
with nifedipine and may produce reflex tachycardia, flushing,
and palpitations. Conduction defects are rare unless there is
underlying conduction disease, a very large ingestion with loss
of receptor specificity, or the presence of coingestants such as
β-blockers.
9,11
10
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