Definition

Cardiomyopathies are diseases of the myocardium that are characterized by myocardial dysfunction. They ultimately affect contractile function, and life-threatening congestive heart failure (CHF) is common to all cardiomyopathies.

Etiology

Cardiomyopathies can be classified according to their pathophysiologic basis in the categories of dilated (congestive), restrictive, and hypertrophic.

Pathophysiology

The cause of dilated cardiomyopathies can be inflammatory or noninflammatory. The inflammatory type or myocarditis usually results from infection. The noninflammatory variety results from idiopathic, toxic, degenerative, or infiltrative processes that destroy the myocardium or cardiac cytoskeleton. The primary clinical symptom is myocardial failure, which presents as ventricular dilation, elevated filling pressures, and pulmonary edema. Dilated cardiomyopathies can be acute or chronic and can lead to a decrease in myocardial contractility, often involving both ventricles. Alcoholic cardiomyopathy is an example of noninflammatory cardiomyopathy that is associated with tachycardia, premature ventricular contractions that progresses to left ventricular (LV) failure and valvular disease.

Clinical symptoms are characterized as “forward” failure or “backward” failure. Symptoms of forward failure may include fatigue, hypotension, and oliguria caused by a decreased organ perfusion.

Symptoms of backward failure may include elevated filling pressures and ventricular failure. The LV dilation and mitral regurgitation (MR) result in orthopnea, paroxysmal nocturnal dyspnea, and pulmonary edema. Symptoms of right-sided failure include hepatomegaly, jugular venous distention, and peripheral edema.

Treatment

Patients with dilated cardiomyopathy (DCM) must avoid unnecessary physical activity and must exhibit total abstinence from alcohol. Patients with CHF are treated with digoxin and diuretics. Vasodilator treatment or an inotrope with vasodilator properties (amrinone or milrinone) may also be helpful. Ventricular arrhythmias are treated with procainamide or quinidine. Because of the increased risk of pulmonary embolism, these patients may be treated with anticoagulants (not proved to be of benefit). Patients with associated collagen vascular disease, sarcoidosis, or inflammation on endocardial biopsy are treated with corticosteroids preoperatively. Tachyarrhythmias can be treated with β-blockers. Patients with CAD and DCM may benefit from coronary revascularization to improve LV function. With advanced CHF, these patients may be candidates for heart transplantation, provided pulmonary hypertension does not exist.

Anesthetic considerations

Excess cardiovascular depression on induction of anesthesia in patients with a history of alcohol abuse may reflect undiagnosed DCM; however, failure of this expected response to intravenous induction agents may reflect a slow circulation time.

During maintenance, myocardial depression produced by volatile agents must be considered. Opiates exhibit benign effects on cardiac contractility but may not produce unconsciousness. In addition, an opioid, nitrous oxide, benzodiazepine technique may cause unexpected cardiac depression. Increases in heart rate associated with surgical stimulation may be treated with β-blockers. Nondepolarizing muscle relaxants that exhibit few cardiovascular effects are advised.

Cardiac filling pressures should guide intravenous fluids; therefore, a pulmonary artery (PA) catheter aids in early recognition of the need for inotropes or vasodilators. Prominent “v” waves reflect mitral or tricuspid regurgitation (TR).

Intraoperative hypotension is treated with ephedrine. Phenylephrine could adversely affect afterload as a result of increased systemic vascular resistance (SVR).

Regional anesthesia may be used in selected patients, although caution is indicated in avoiding abrupt sympathetic blockade as seen in spinal or epidural anesthesia.

Prognosis

The prognosis for patients with DCM is poor, with a 5-year survival rate of 25% to 40%. The cause of death in 75% of these patients is CHF. Pulmonary embolism or sudden death from arrhythmia is found in more than 50% of these patients on autopsy.