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CARDIOLOGY CASEBOOK |
A 76-year-old retired, decorated police officer consulted his family physician because of palpitations 1 day in duration. He had been feeling well and physically active doing household chores and yard work: he was not taking any medications. Although uncomfortable because of the palpitations; he was not dyspneic and had no chest pains. On physical examination, his blood pressure was 130/75 mm Hg in the right arm, and the lungs were clear on auscultation. The point of maximal cardiac impulse was in the 5th intercostal space at the midclavicular line. The ventricular rate was 98 beats/min and very irregular. An electrocardiogram (ECG) confirmed the physician’s impression of a diagnosis of atrial fibrillation (AF). There were no acute repolarization changes (ST-T) and no abnormal Q waves. The jugular venous pulses were not elevated and there was no hepato-jugular reflux, thus eliminating the possibility of congestive heart failure. The patient was reassured that the arrhythmia could be managed and he would be able to return to full activity.
QUESTIONS
ANSWERS
1. f. any of the above in addition to "c."
Atrial fibrillation is a chaotic atrial rhythm with an atrial rate so fast (350–600 discharges/min) that it makes it difficult to discern P waves on an ECG (Figure 1
). Many atrial impulses encounter refractory tissue at the AV node, and as a result only some of the depolarizations are conducted to the ventricle in a very irregular rhythm. Atrial fibrillation, the most common sustained arrhythmia is found in 0.5% of the general population, affects over 2 million patients in the United States, and is more prevalent in males.1,2 The incidence of AF is approximately 1% in patients under 60 years of age and over 8% in those more than 80 years of age.3 Seventy percent of patients with AF are 65 to 80 years of age. The increased prevalence of AF in the elderly may be the result of the longer life span currently experienced in patients with chronic diseases. AF is associated with cardiac diseases (eg, hypertensive heart disease, rheumatic mitral stenosis, coronary artery disease, congestive heart failure) and noncardiac diseases (eg, hyperthyroidism, hypoxic pulmonary lesions, surgery, alcohol intoxication, sleep apnea, and obesity). There is a 5-fold increased risk of stroke and a 2-fold increase in mortality in patients with AF, even after adjustments are made for preexisting cardiovascular diseases.2,4 Lone AF is a diagnosis in patients less than 60 years of age who have no evidence of other cardiovascular diseases, hypertension, or diabetes. Echocardiography can confirm the lack of structural heart disease. In lone AF, the risk of stroke is low and anticoagulation for stroke prevention is considered unnecessary; nevertheless, low-dose aspirin is still used because epidemiologically aspirin lessens the risk of stroke and acute myocardial infarction (MI) in patients with lone AF. The incidence of stroke in patients with lone AF is low; nevertheless, the occurrence of a cerebral vascular accident can be devastating.5
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2. b. rhythm control
c. anticoagulation
Pharmacological conversion therapy aimed at rhythm control (reestablishing sinus rhythm) has been achieved with any of the following agents: ibutilide, flecainide, dofetilide, propafenone, or amiodarone; moderate efficacy has been observed with quinidine therapy. The chief drawbacks in antiarrhythmic drug therapy are the adverse reactions to these drugs and the potential hazards of torsades de pointes that can occur in the presence of a prolonged QT interval. Torsades de pointes translates to "twisting of the points" and is a polymorphic ventricular tachycardia presenting as varying amplitudes of the QRS as if the complexes are "twisting" about the baseline. The dangers of torsades de pointes are syncope and ventricular fibrillation (Figure 2).
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3. e. all of the above
Treatment of persistent AF aimed at rate control is clinically simple and less hazardous than therapy for rhythm control. Atenolol, metoprolol, diltiazem, and verapamil have been used with varying degrees of effectiveness in the control of the ventricular response rate in AF. Rate control can be achieved with the combined use of digoxin, and a ß-blocker titrated to a targeted ventricular response rate appropriate at rest and during moderate exercise, for example, walking 30 yards at a brisk pace (L.L., personal observation). Age, the physical state, and the clinical state influence the optimal resting and exercise ventricular response rate in AF. Rate control is appropriate when the ventricular response with moderate exertion is not excessive. As a general rule, with normal left ventricular function, a resting heart rate of 60 to 70 beats/min and rates of 80 to 90 beats/min with moderate exertion are appropriate.
AV nodal blockade may often lead to secondary bradycardia and subsequent pacemaker implantation for rate support. Hemodynamically significant breakthrough rapid ventricular rates, or the occurrence of disabling symptoms despite adequate AV nodal blocking agents, may require AV node ablation. Following AV node ablation, implantation of a permanent pacemaker (rate responsive VVI or DDD) is required to provide physiological rate support. As with any therapeutic regimen in AF, anticoagulation is standard therapy.
Summary
AF is the most commonly sustained clinical arrhythmia, with an incidence that increases 2-fold with every decade after 55 years of age. There is an estimated prevalence of about 2 million Americans with AF. AF is the most frequent principal diagnosis of cardiac arrhythmias, responsible for approximately 265 000 hospital admissions annually.7 These statistics make managing AF a major issue. The therapeutic goal in the past was to restore and maintain sinus rhythm. Cardioversion was successful and often used; however, maintaining sinus rhythm following conversion required the use of antiarrhythmic drugs that were potentially proarrhythmic. The AFFIRM trial proved that rhythm control of AF has no mortality benefits over rate control therapy.7 In fact, in elderly patients, rhythm control was associated with a higher mortality than rate control.9 The quality of life substudy of the AFFIRM trial revealed no differences in the quality of life between the rate- and rhythm-controlled patients.
Current therapy recommends that patients with AF can be successfully managed and will experience an equal quality of life when treated to control the heart rate or to maintain a sinus rhythm following conversion of AF. However, rate control especially in the elderly is preferable.
ACKNOWLEDGMENT
Supported in part by a grant from the Applebaum Foundation in loving memory of Joseph Applebaum.
Request for reprints: Louis Lemberg, MD, University of Miami School of Medicine, Division of Cardiology (D-39), P.O. Box 016960, Miami, FL 33101.
Conti CR. Stroke and atrial fibrillation: to anticoagulate or not. Clin Cardiol. 1993;16:29–30.
Gronefeld GC, Lilienthal J, Kuck KH, et al. Impact of rate versus rhythm control on quality of life in patients with persistent atrial fibrillation. Eur Heart J. 2003;24:1430–1436.
Hagens VE, Ranchor AV, Van Sonderen E, et al. Effect of rate or rhythm control on quality of life in persistent atrial fibrillation. J Am Coll Cardiol. 2004;43:241–247.
Marshall DA, Levy AR, Vidaillet H, et al. Cost-effectiveness of rhythm versus rate control in atrial fibrillation. Ann Intern Med. 2004;141:653–661.
Newman D. Atrial fibrillation and quality of life: Clarity or evidence-based confusion? Am Heart J. 2005;149:4–6.[Medline]
Opolski G, Torbicki A, Kosior D, et al. Rhythm control versus rate control in patients with persistent atrial fibrillation: results of the HOT CAFE Polish Study. Kardiol Pol. July 2003;59:1–16.[Medline]
Singh BN, Singh SN, Reda DJ, et al. Amiodarone versus sotalol for atrial fibrillation. N Engl J Med. 2005;352:1861–1872.
The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) Investigators. A comparison of rate control and rhythm control in patients with atrial fibrillation. N Engl J Med. 2002;347:1825–1833.
Wyse DG. Rhythm versus rate control trials in atrial fibrillation. J Cardiovasc Electrophysiol. 2003;14:S35–S39.[Medline]
VanGelder IC, Hagens VE, Bosker HA, et al. A comparison of rate control and rhythm control in patients with recurrent persistent atrial fibrillation. N Engl J Med. 2002;347:1834–1840.
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