Arrhythmias

Both tachy- and bradyarrhythmia may be observed in HIV-infected patients in rela­tion to structural alterations of the endo­cardium (infective endocarditis), of the myocardium (myocarditis, dilated cardiomy­opathy), and of the pericardium (infective and neoplastic pericarditis and myoperi­carditis).

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Fig.4 Dilated cardiomyopathy in an HIV-infected patient (four-cham­ber apical view). Left ventriculalr ejection fraction: 25%. Note the dilatation of both left and right cardiac chambers. RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle

Side effects of both antiretroviral drugs or drugs used in the treatment and/or prophylaxis of opportunistic infections and neoplasms. Gan­ciclovir, amphotericin B, Cotrimoxazole (trimethoprim-sulfamethoxazole), and pen­tamidine may cause Torsades de pointes (TdP) that can degenerate into ventricular fibrilla­tion and sudden cardiac death (Fig. 5). Torsades de pointes (TdP) is related to pro­longation of the ventricular action potential duration (QTc interval of the electrocardio­gram >0.45 s) and it has also been described in relation to the administration of macrolide antibiotics (erythromycin, clarithromycin). Uncorrected electrolyte alterations (e.g., hy­pokalemia, hypomagnesemia, hypocalcemia) related to malnutrition and/or to chronic di­arrhea or electrolyte imbalances induced by diuretics are also associated. These alter­ations, which should be evaluated and treat­ed as early as possible, may further contribute to prolonging the QTc interval.

Use of central nervous system stimulant drugs (e.g., cocaine, amphetamines). Cocaine abuse has been associated with myocarditis, myocardial infarction, and dilated car­diomyopathy even in HIV-negative subjects, possibly because of intermittent microvas- cular spasm resulting from catecholamine surges associated with a high risk of ventric­ular arrhythmia.

Particularly in the ED, the first line of therapy for TdP is to stop medications sus­pected of prolonging the QT interval and to correct electrolyte imbalances. Intravenous­ly administered magnesium sulfate is imme­diately indicated (loading dose of 1-2 g, mixed in 50-100 ml of saline, over 5-10 min followed by a continuous infusion of 1.0-2.0 g/h over 4-6 h), whereas i.v. infu­sion of isoproterenol (0.01-0.02 mcg/kg per minute) in the absence of known or suspect­ed coronary artery disease may accelerate the heart rate and suppress ventricular arrhythmias while temporary ventricular pacing (overdrive pacing) is initiated [1].

In HIV-infected patients, hemodynami- cally stable sustained monomorphic wide- QRS complex tachycardia is another diag­nostic challenge for the emergency physi­cian, as ventricular tachycardia (VT) must be distinguished from supraventricular tachycardia (SVT). In particular, SVT with an accessory pathway, preexisting bundle­branch block, or rate-dependent bundle­branch block should be considered. SVT with aberrant conduction is frequently observed in HIV-infected patients with dilated cardiomyopathy and histological diagnosis of myocarditis [1] (Fig. 6). In patients that are hemodynamically stable with no symptoms or clinical evidence of tis­sue hypoperfusion or shock, initial manage­ment should proceed under the presump­tion that the arrhythmia is VT, and electric cardioversion is the preferred therapy. If electrical cardioversion is not possible, empiric pharmacological therapy may be necessary with agents such as procainamide or amiodarone, which possess efficacy against VT and SVT and are also acceptable in patients with accessory pathway conduc­tion [1].

Fig. 5 Run of Torsade de pointes in an HIV-infected subject receiving pentamidine as prophylaxis for Pneumocystis carinii pneumonia during Holter electrocardiographic monitoring (lead CM5). Note the prolongation of the QT interval of the QRS complex following the arrhythmic run (0.50 s). (From [1], with permission from Elsevier)

Procainamide is administered in an infu­sion of 20 mg/min until the arrhythmia is suppressed or hypotension ensues, or when a total of 17 mg/kg of the drug has been given. Amiodarone is administered as 150 mg over 10 min, followed by 150 mg over the next 30 min, and then 1 mg/min infu­sion for 6 h followed by 0.5 mg/min, to a maximum daily dose of 2 g. If the patient is in shock or in congestive heart failure (hemodynamically unstable), a wide-QRS complex tachycardia should be presumed to be VT, which requires immediate termina­tion of synchronized cardioversion [1].