The Cardiomyopathies: Diagnosis and ICU Management

G. William Dec

I. BACKGROUND

A. Cardiomyopathies are a diverse group of diseases characterized by primary myocardial involvement.

B. Classified by anatomic appearance and physiologic abnormalities (Table 26-1).

1. Dilated cardiomyopathies (DCMs).

2. Hypertrophic cardiomyopathies (HCMs).

3. Restrictive cardiomyopathies (RCMs).

II. DILATED CARDIOMYOPATHIES

A. Background.

1. Cardiac enlargement (left ventricular [LV] end-diastolic dimension >55 mm) and decreased contractile function (left ventricular ejection fraction [LVEF] < 45%) are disease hallmarks.

2. Reversible causes should always be excluded (Table 26-2).

3. A familial pattern is present in approximately 25% of cases; clinical clues are the following:

a. Concomitant skeletal myopathy, often mild.

b. Sensorineural hearing loss.

B. Pathophysiology.

1. Impaired systolic contractile function leads to ventricular dilatation via the Frank-Starling mechanism.

2. Functional mitral and/or tricuspid regurgitation is common as annular displacement occurs secondary to progressive ventricular dilatation.

3. Chronic dyspnea due to elevated filling pressures is the most frequent symptom. Acute pulmonary edema is uncommon except during periods of stress (e.g., infection, change in cardiac rhythm, surgical procedures).

4. Physical findings.

a. Jugular venous distension and hepatojugular reflux.

b. S4 and S3 gallops may wax and wane in intensity.

c. Mitral or tricuspid regurgitation murmurs (1-3/6 in intensity) are often audible.

d. Clear lungs are most commonly due to enhanced pulmonary lymphatic drainage.

e. Liver enlargement and peripheral edema are seen in fewer than 50% of cases.

TABLE 26-1 Hemodynamic and Morphometric Features of the Cardiomyopathies

Features	Dilated	Hypertrophic	Restrictive
LV ejection fraction	<45%	65%-90%	50%-70% <40% (late)
LV cavity size	Increased	Normal or decreased	Normal Increased (late)
Stroke volume	Markedly decreased	Normal or increased	Normal or decreased
Volume to mass ratio	Increased	Decreased	Markedly decreased
Diastolic compliance	Normal to decreased	Markedly decreased	Markedly decreased
Other features	Mild/moderate MR/TR are common	Dynamic obstruction	Often mimics constrictive pericarditis
DCM: dilated cardiomyopathy; HCM, hypertrophic cardiomyopathy; LV, left ventricular; MR, mitral regurgitation; TR, tricuspid regurgitation. Adapted from DeSanctis RW, Dec GW. The cardiomyopathies. Section 1, Subsection XIV, in Scientific American Medicine, Dale DC and Federman D (eds). Copyright 1995, Scientific American, Inc. (Table 1), with permission.

C. Diagnosis.

1. Echocardiography is the most useful noninvasive modality to assess systolic and diastolic function, chamber size, and ventricular wall thickness and to exclude significant valvular pathology (Table 26-3).

2. Patients with known DCM and stable symptoms require little additional diagnostic testing.

a. Serum electrolytes, Mg²⁺, and B-type natriuretic peptide (BNP) may help direct treatment and risk stratification.

b. 12-lead ECG and CXR.

c. Preoperative echocardiography is generally unnecessary in patients who have been clinically stable at home and are ambulatory.

d. Preoperative pharmacologic stress testing with cardiac perfusion imaging should be considered for patients with known or suspected ischemic cardiomyopathy and either worsening heart failure or anginal symptoms or in whom a major surgical procedure is planned.

D. Treatment.

1. Elective surgery should be postponed for patients with newly diagnosed DCM to initiate pharmacologic therapy and allow time (6 to 12 weeks) for spontaneous recovery of systolic function.

2. Heart failure decompensation is the most frequent complication during ICU hospitalization.

3. Individuals whose LVEF <20% are at increased risk for developing perioperative heart failure, atrial fibrillation, ventricular arrhythmias, and cardiorenal syndrome.

TABLE 26-2 Causes of Potentially Reversible DCM

Toxins Ethanol Cocaine Antiretroviral agents (AZT, ddI, ddC) Phenothiazines, clozapine Chemotherapeutic agents (anthracyclines, trastuzumab) Metabolic abnormalities Nutritional (thiamine, selenium, carnitine, and taurine deficiencies) Endocrinologic (hypothyroidism, acromegaly, thyrotoxicosis, pheochromocytoma) Electrolyte disturbances (hypocalcemia, hypophosphatemia) Inflammatory/infectious/infiltrative Infectious
	Viral (coxsackievirus, adenovirus, cytomegalovirus, parvovirus) Parasitic (toxoplasmosis) Spirochetal (Lyme disease)
Inflammatory/Infiltrative
	Collagen vascular disorders (sarcoidosis) Hypersensitivity myocarditis Hemochromatosis Sarcoidosis
Miscellaneous Tachycardia induced Idiopathic Peripartum
AZT, zidovudine (azidothymidine); ddI, didanosine (dideoxyinosine); ddC, zalcitabine (dideoxycytidine).

4. The cornerstones of pharmacologic therapy should include:

a. A loop diuretic (furosemide, bumetanide, or torsemide).

b. An ACE inhibitor or angiotensin receptor blocker (ARB).

c. A β-blocker.

d. Digoxin and aldosterone antagonists are generally reserved for patients with chronic advanced (New York Heart Association [NYHA] class III or IV) symptoms.

5. Acute volume expansion should be avoided as it will exacerbate atrioventricular (AV) valvular regurgitation and lead to decreased forward stroke volume and cardiac index.

6. Hemodynamic monitoring with a pulmonary artery catheter should be considered for major surgical procedures in DCM patients who have

a. Recent decompensation in heart failure symptoms.

b. Myocardial infarction within the previous 3 months.

c. Moderate/severe stenotic valvular heart disease.

TABLE 26-3 Diagnostic Evaluation of New-Onset DCM

Class I studies (usually indicated, always acceptable)

CBC and urinalysis

Electrolytes, renal function, glucose, phosphorus, calcium, albumin, TSH level

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