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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3063_Библиотеки_им_академика_М_И_Перельмана
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CCS NOTE
“Fluttering” or “palpitations” in a case is not a sign of hemodynamic instability, but it
does mean you should order an EKG.
Initial Management
Setting: emergency room
Diagnostic/Therapeutic Plan
Test Results
Assessment
The presentation of palpitations and a rapid pulse is suggestive of a cardiac arrhythmia. Sinus
tachycardia is due to underlying medical disorders such as fever, pain, anxiety, dyspnea, and
many other causes.
Thyrotoxicosis6.
Sinus tachycardia with ectopy7.
Hypoglycemia8.
Electrocardiogram
Irregular tachycardia with absent P waves
Ventricular response 140/min
Pulse irregularly irregular
271
CCS NOTE
If the EKG does not reveal the etiology of the palpitations, order telemetry monitoring
or ambulatory Holter monitoring.
The irregularly irregular pulse should make you suspect atrial fibrillation. Prompt evaluation of
the patient’s hemodynamic status is crucial. An electrocardiogram will confirm the diagnosis.
By itself, the sensation of “fluttering in his chest” or palpitations is extremely nonspecific.
Many patients with palpitations are never found to have a cardiac problem of any kind. Any
form of arrhythmia may give palpitations. Atrial flutter and supraventricular tachycardia will
generally not give an irregularly irregular heart rhythm.
The tests described below represent a systematic evaluation to determine the etiology of atrial
fibrillation.
Further management plan Results
Thyroid function tests
1.
Normal
1.
Cardiac enzymes
2.
Normal
2.
Echocardiogram
3.
Normal ejection fraction; left atrial enlargement; no pericardial
disease
3.
Arterial blood gases
4.
Normal
4.
272
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CCS NOTE
The cases in this course give groups of diagnostic tests because each case is meant to
cover a whole area of medicine. You might not have to order all these tests if the
diagnosis on the CCS case is obvious.
Treatment Plan
Discussion
Atrial fibrillation (“a-fib”) is most commonly due to hypertension. Chronic hypertension leads
to increased afterload and as a result the heart has to increase contractility to maintain the
stroke volume. This increase in contractility places the heart under a high pressure state which
leads to concentric hypertrophy. Concentric hypertrophy causes a stiff, non-compliant left
ventricle. This causes left atrial dilatation.
Mitral stenosis and mitral regurgitation may also cause atrial fibrillation. A-fib may also occur
in the setting of any underlying heart disease, lung disease, or hyperthyroidism. The differential
diagnosis includes multifocal atrial tachycardia, which most often can be distinguished by the
presence of 3 distinct P-wave morphologies on the electrocardiogram. Paroxysmal
supraventricular tachyarrhythmias have a regular rhythm and more commonly must be
distinguished from atrial flutter. Precipitating conditions such as thyrotoxicosis, pulmonary
embolus, pericarditis, alcohol intoxication, the use of catecholamine-like drugs, and
myocardial infarction should be excluded.
IV diltiazem
Admit to telemetry unit
273
CCS NOTE
On the CCS, you must order drugs by a specific name, not just by class.
There are 3 things to consider with a-fib:
Treatment is directed at restoring normal sinus rhythm, and preventing the paroxysms and
slowing conduction through the atrioventricular node (with agents like digoxin, beta-adrenergic
blocking agents, and CCBs). When a patient presents with a-fib and rapid ventricular response,
the first step is to determine stability. Emergency cardioversion is indicated for patients with
hemodynamic instability or angina. For patients who are stable, rate control should be
achieved with an AV nodal blocking agent (i.e., a beta-blocker such as metoprolol or esmolol,
or a non-dihydropyridine CCB such as diltiazem or verapamil). Digoxin is a good option for a
patient with decompensated systolic heart failure, but not good for a normal cardiac patient
who is ambulatory. It will only control the resting HR.
Rate control is usually preferred. Rhythm control is used when patients cannot tolerate the
symptoms of atrial fibrillation (shortness of breath or palpations) or cannot be rate-controlled.
For rhythm control, elective DC cardioversion is preferred. Chemical cardioversion may also
be used. Amiodarone, sotalol, dofetilide, ibutilide, propafenone, and flecainide may all be
used. In most case these agents will have to be continued for maintenance. Once rate control is
achieved, the next step is to decide whether to continue with rate control or to proceed with
rhythm control.
Rate control
Anticoagulation
Rhythm control
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Long-term success of maintaining sinus rhythm is less likely if the arrhythmia has been present
for a long period of time or if the left atrial size >45 mm. Anticoagulation should be given for 3
wks before elective cardioversion if the arrhythmia has been present for several days or if the
patient is at increased risk for stroke (cardiomyopathy, rheumatic mitral valve disease,
prosthetic valves, left atrial enlargement, or a previous stroke). Another option before elective
cardioversion is to perform a trans-esophageal echocardiogram to exclude the presence of a
thrombus.
Routine cardioversion of atrial fibrillation is not indicated. The vast majority of those who
develop atrial fibrillation will not be successfully converted to sinus rhythm because they will
slip back into atrial fibrillation. Therefore, rate control and anticoagulation with warfarin is the
standard of care.
For a patient with non-valvular a-fib, we use the CHADS2 score to determine if an
anticoagulant is needed.
Each condition gets 1 point, except for stroke/TIA which gets 2 points.
Score of 0 in lone a-fib Give aspirin
Score of 1 Give aspirin or anticoagulant
Score of 2+ Give anticoagulant
There are a few options for anticoagulation:
C is for CHF
H is for HTN
A is for age >75
D is for DM
S is for stroke or TIA
275
These new agents have been clinically compared to warfarin. Results have shown that they are
non-inferior or superior for stroke prevention, with less intracranial hemorrhaging (though
more GI bleeding).
Long-term rate control with anticoagulation is equal in efficacy to elective cardioversion with
either medication or electrical shock. Digoxin is preferable for rate control in patients with
poor ventricular function. Diltiazem is just as rapid as verapamil with fewer adverse effects.
Verapamil produces a rapid effect but because of its profoundly negative
inotropic/dromotropic activity, it must not be used when there is evidence of ventricular
dysfunction or conduction block. Beta-blockers such as metoprolol and propranolol are
options, as well, to control rate; similar to calcium blockers, they are relatively
contraindicated with atrioventricular block.
Most patients will go back into atrial fibrillation and will require anti-arrhythmic agents for
maintenance, and anti-coagulation indefinitely. Amiodarone is superior for maintaining the
patient in sinus rhythm after conversion when there is systolic dysfunction. The only 2 agents
that are safe for rhythm control in systolic dysfunction are amiodarone and dofetilide.
Ablation is the answer for patients who cannot tolerate anti-arrhythmic agents and have
symptoms while in atrial fibrillation. If they have a high CHADS2 score, they will require
anticoagulation after ablation indefinitely.
Final Diagnosis
Atrial fibrillation with a rapid ventricular response
Warfarin with goal INR 2–3
Dabigatran is an oral direct thrombin inhibitor
Rivaroxaban and abixaban are oral factor Xa inhibitors
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CCS NOTE
Patients with atrial rhythm disorders do not have to go to the intensive care unit if the
rate has been controlled to <100/min. They can go to the ward with telemetry
monitoring.
Basic Science Correlate
Let’s understand the drugs used to target the different phases of the action potential, and
their mechanisms of action. Antiarrhythmic drugs are useful not only for treatment of
atrial fibrillation but also for the other cardiac arrhythmias. The 4 main classes of
antiarrhythmic drugs are detailed below:
Class I: Na
+
channel
blockers
Class 1A
Class 1B
Increase action potential duration (APD) and effective refractory
period (ERP)
Also blocks K+ channels (prolongs repolarization)
e.g., quinidine, procainamide
Cautions and contraindications:
Prolongation of QRS and increased QT interval—
Block inactivated channels — increase threshold for excitation
277
Class II: beta blockers
Class III: K
+
channel
blockers
Class IV: Ca
2+
channel
blockers
Decrease APD due to block of slow Na + currents
e.g., lidocaine, mexiletine
Lidocaine is safe in ischemic tissue
Class 1C
No effect on APD
No ANS effects
e.g., flecainide
Cautions and contraindications:
Limited use due to proarrhythmogenic effects
—
Prevent β-receptor activation
Decrease SA and AV nodal activity
Decrease slope of phase 4 of AP in pacemaker cells
e.g., propranolol (nonselective), acebutolol and esmolol
(cardioselective)
Slows phase 3 (repolarization) of AP
Increase APD and ERP
e.g., amiodarone, sotalol
Cautions and contraindications:
Long QT syndrome
Decrease phase 0 and phase 4
Decrease SA and AV nodal activity
e.g., verapamil, diltiazem
Cautions and contraindications:
Additive AV block with β-blockers and digoxin
Verapamil displaces digoxin from tissue binding sites
278
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CLINICAL PEARL
Class IA and III antiarrhythmic drugs block K
+
channels, prolonging repolarization and
increasing the QT interval on EKG. QT prolongation leads to Torsades de pointes.
Hypokalemia, hypomagnesemia, and hypocalcemia may also inhibit the opening of the
delayed rectifying potassium channels and prolong the refractory period, leading to QT
prolongation. Other drugs such as macrolides, fluoroquinolones, and antipsychotics
such as haloperidol have the same effect.
279
Case 9
Chief Complaint
“I’m having palpitations.”
History and Physical Examination
A 65-year-old man, recently discharged from the hospital after being treated for an
anterior-wall myocardial infarction, is brought to the emergency room by his family
because of palpitations. As you are examining him, he becomes unresponsive and loses
his pulse.
Differential Diagnosis
Initial Management
Setting: emergency department
Diagnostic/Therapeutic Plan
Ventricular fibrillation
1.
Ventricular tachycardia
2.
Acute myocardial infarction
3.
Asystole
4.
Electromechanical dissociation
5.
Pulmonary embolus
6.
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