Cardiomyopathy calcium channel blockers

In addition to angina, calcium channel blockers have well-documented efficacy in hypertension (see Chapter 11) and supraventricular tachyarrhythmias (see Chapter 14). They also show moderate efficacy in a variety of other conditions, including hypertrophic cardiomyopathy, migraine, and Raynaud s phenomenon. Nifedipine has some efficacy in preterm labor but is more toxic and not as effective as atosiban, an investigational oxytocin antagonist (see Chapter 17). 

Severe conduction disturbances can also occur if calcium channel blockers are used in hypertrophic cardiomyopathy (46), but these drugs are used in this condition (47). 

Severe recurrent, but usually reversible hjrpertrophic cardiomyopathy has been infrequently reported, both in adults and children (SEDA-19, 352) (SEDA-20, 346). Based on experimental data and one additional case report, the interaction of tacrolimus with calcium channel blockers in the cardiac muscle has been suggested as a possible mechanism (SEDA-21, 390). However, the role of tacrolimus in the development of cardiomyopathy is still hjrpothetical. Echocardiographic abnormalities were relatively common before and after liver transplantation in 12 adult patients, and there was no clear evidence that oral tacrolimus specifically alters cardiac function (13). Other investigators did not show differences in heart weight, ventricular thickness, or valve circumferences between 67 Uver transplant recipients treated with tacrolimus and 72 non-transplanted patients who died from end-stage liver disease (14). In addition, more than 80% of patients in both groups had left ventricular hypertrophy. 

Verapamil, proprietaiy name Calan, is a calcium channel blocker that is effective in the treatment of various cardiovascular disorders, including angina (classical and variant), arrhythmias (paroxysmal supraventricular tachycardia), atrial flutter, atrial fibrillation, hypertrophic cardiomyopathy (idiopathic hypertrophic subaortic stenosis), hypertension, congestive heart failure, and Raynaud s phenomenon, along with the preservation of ischemic myocardium and the treatment of migraine headaches. 

Udelson JE, Bonow RO. Left ventricular diastolic function and calcium channel blockers in hypertrophic cardiomyopathy. In Gaasch WH, Le Winter MM, eds. Left Ventricular Diastolic Dysfunction and Heart Failure. Philadelphia, Lea Febiger, 1994 465. 

Treatment recommendations cannot be derived firom such limited experience. Individual cases have been treated with calcium channel blockers and diuretics (26), nifedipine and diuretics (27), or sildenafil (27). Nifedipine decreased echo estimated RV systolic pressures from 90 to 84 mmHg (27). Median survival for all reported cases was 157 days (range 19-1036 days). Calcium channel blockers (28) and digoxin (29) avidly bind amyloid fibrils, producing locally toxic drug-myocardial interaction. Calcium channel blockers can worsen CHF in patients with amyloid cardiomyopathy and should be used cautiously (30). 

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