eMedicine Specialties > Cardiology > Myocardial Disease and Cardiomyopathies

Cardiomyopathy, Hypertrophic: Differential Diagnoses & Workup

Author: Michael E Zevitz, MD, Assistant Professor of Medicine, Finch University of the Health Sciences, The Chicago Medical School; Consulting Staff, Private Practice
Contributor Information and Disclosures

Updated: Aug 27, 2009

Differential Diagnoses

Aortic Stenosis
Cardiomyopathy, Restrictive
Glycogen Storage Disease, Type II

Other Problems to Be Considered

Aortic stenosis, supravalvular

Workup

Laboratory Studies

  • No specific laboratory blood tests are required in the workup of HCM.
  • Genetic testing is not widely available at this time but is becoming increasingly available in this disease setting. In research situations or in larger pedigrees, genotyping is informative for the identification of additional family members once the proband's genotype has been determined.

Imaging Studies

  • Two-dimensional echocardiography and Doppler studies
    • Two-dimensional echocardiography is diagnostic for HCM. Color Doppler flow studies typically reveal mitral regurgitation.12
    • Spectral continuous-wave Doppler studies in patients with obstructive HCM reveal an elevated flow velocity across the LV outflow tract. Severe obstructive HCM typically has a flow velocity greater than 4 m/s, and a gradient across the LV outflow tract of greater than 50 mm Hg is considered severe.
    • Echocardiography also typically reveals diastolic dysfunction with reduced LV compliance and a mitral valve ratio of E wave to A wave of less than 1 (usually <0.8). Systolic function is good, and, in fact, the LV ejection fraction usually is high to normal at the time of diagnosis. The LV diameter is at the lower limit of normal or smaller than normal.
    • The hallmarks of the obstructive type of HCM consist of systolic anterior motion of the anterior mitral valve leaflet and asymmetric septal hypertrophy with a ratio of septal wall thickness to posterior wall thickness of greater than 1.4:1.
    • The septum not only is relatively thicker than the posterior wall, it is also typically at least 4-6 mm thicker than normal for each age group. Massive hypertrophy with septal wall thickness of greater than 25 mm has been noted in rare cases, particularly in infants with glycogen storage defects, as are observed in patients with Pompe disease.
    • An unusual echocardiographic pattern consisting of a ground-glass appearance has been noted in portions of the hypertrophied myocardium in some patients. This pattern may be related to the abnormal cellular architecture and myocardial fibrosis that have been observed in pathological studies.
    • A narrowing of the LV outflow tract occurs in many patients with HCM. This contributes to the creation of a pressure gradient in a small number of patients.
    • The hallmark of HCM associated with a pressure gradient is the abnormal systolic motion of the anterior leaflet of the mitral valve (ie, systolic anterior motion) and, in rare cases, the systolic motion of the posterior leaflet. Three explanations for the systolic anterior motion of the mitral valve have been offered, as follows:
      • The mitral valve is pulled against the septum by contraction of the papillary muscles, which occurs because of the valve's abnormal location and septal hypertrophy altering the orientation of the papillary muscles.
      • The mitral valve is pushed against the septum because of its abnormal position in the outflow tract.
      • The mitral valve is drawn toward the septum because of the lower pressure that occurs as blood is ejected at high velocity through a narrowed outflow tract (Venturi effect).
    • Several other echocardiographic findings may be present, as follows:
      • A small LV cavity may be present secondary to marked hypertrophy of the myocardium and encroachment into the LV cavity.
      • Reduced septal motion and thickening during systole may occur, particularly of the upper septum, resulting from disarray of the myofibrillar architecture and abnormal contractile function.
      • The motion of the posterior wall may be normal or increased.
      • The rate of closure of the mitral valve in mid diastole may be reduced secondary to a decrease in LV compliance or abnormal transmitral flow during diastole.
      • Mitral valve prolapse, a rare echocardiographic occurrence in HCM, may be present.
    • Partial systolic closure or, more commonly, coarse systolic fluttering of the aortic valve related to turbulent blood flow in the outflow tract may occur. Abnormalities in diastolic function may be demonstrated by echocardiography and Doppler recordings in approximately 80% of patients with HCM, independent of the presence or absence of a systolic pressure gradient.
    • The presence of mitral regurgitation virtually always is confirmed by Doppler echocardiography in patients with HCM who have a systolic gradient.
    • In general, a summary of echocardiography findings includes abnormal systolic anterior leaflet motion of the mitral valve, LV hypertrophy, left atrial enlargement, small ventricular chamber size, septal hypertrophy with septal-to-free wall ratio greater than 1.4:1, mitral valve prolapse and mitral regurgitation, decreased mid aortic flow, and partial systolic closure of the aortic valve in mid systole.
  • Chest radiograph
    • Chest radiograph (CXR) findings are variable. The cardiac silhouette may range from normal to markedly increased.
    • Left atrial enlargement frequently is observed, especially when significant mitral regurgitation is present. This is manifested by a "double-density" appearance on CXR.
  • Radionuclide imaging
    • Radionuclide imaging with thallium or technetium may show reversible defects, mostly in the absence of coronary artery disease.
    • Thallium or technetium scintigraphy may reveal defects in myocardial perfusion, even in the setting of angiographically normal coronary arteries.
  • These reversible defects evident on radionuclide scanning are more common in children and adolescents with a history of sudden death or syncope, which suggests that myocardial ischemia is a significant factor in the mechanism of the demise of younger patients with HCM.

Other Tests

  • Electrocardiography
    • Common findings include ST-T wave abnormalities and LV hypertrophy. Other findings observed on ECG include axis deviation (right or left), conduction abnormalities (P-R prolongation, bundle-branch block), sinus bradycardia with ectopic atrial rhythm, and atrial enlargement. One mutation has been identified that is associated with both HCM and Wolff-Parkinson-White syndrome.
    • Uncommon findings include an abnormal and prominent Q wave in the anterior precordial and lateral limb leads, short P-R interval with QRS suggestive of preexcitation, atrial fibrillation (poor prognostic sign), and a P-wave abnormality, including left atrial enlargement.
  • Holter monitoring and event electrocardiography: Findings commonly include atrial and ventricular ectopy, sinus pauses, wandering atrial pacemaker, atrial tachycardia, atrial fibrillation and/or flutter, and nonsustained ventricular tachycardia.

Procedures

  • Cardiac catheterization
    • Although not required for the diagnosis of hypertrophic cardiomyopathy, a diagnostic cardiac catheterization is useful to determine the degree of outflow obstruction, cardiac hemodynamics, diastolic characteristics of the left ventricle and LV anatomy, and, of particular importance, the coronary anatomy. Cardiac catheterization is also reserved for situations when invasive modalities of therapy, such as a pacemaker or surgery, are being considered.
    • Therapeutic cardiac catheterization interventions, utilized in well selected cases of hypertrophic cardiomyopathy, include transcatheter septal alcohol ablation to relieve the LV outflow obstruction by intentional infarction of a portion of the interventricular septum.
    • Cardiac catheterization frequently discloses diminished diastolic left ventricular compliance, and in cases of obstructive hypertrophic cardiomyopathy, a systolic pressure gradient within the body of the left ventricle which is separated from a subaortic chamber by the second septum and anterior leaflet of the mitral valve and abuts the septum. The subaortic pressure gradient may be quite labile and may very between 0 and 175 mm Hg in the same patient under different conditions.
    • The arterial pressure tracing found on cardiac catheterization may demonstrate a "spike and dome" configuration similar to the carotid pulse recording. As a consequence of diminished left ventricular compliance, the mean left atrial pressure and, particularly, the a wave, in the left atrial pressure pulse and left ventricular end-diastolic pressures are usually elevated.
    • Artifactual outflow gradients may occur if the left ventricular catheter becomes entrapped in the trabeculae of a markedly hypertrophied left ventricle. 
    • Cardiac output may be depressed in patients with long-standing severe gradients, but, in the majority of patients, it is normal. Occasionally, cardiac output is elevated in patients with markedly hyperdynamic left ventricular systolic function.
    • Hemodynamic abnormality in hypertrophic cardiomyopathy is not limited to the left side of the heart. Approximately one fourth of patients demonstrate pulmonary hypertension. It is usually mild, but, in some cases, it can be moderate to severe, due (at least in part) to elevated mean left atrial pressures as a consequence of diminished left ventricular compliance. A pressure gradient in the right ventricular outflow tract occurs in approximately 15% of patients who have obstruction to left ventricular outflow and appears to result from markedly hypertrophied right ventricular tissue. Right atrial and right ventricular end-diastolic pressures may be slightly elevated.
    • A feature characteristic of hypertrophic cardiomyopathy is the variability and lability of the left ventricular outflow gradient.  A patient may demonstrate a large gradient on one occasion and have none at another time. In some patients without a resting gradient, it may be temporarily provoked.
    • Three basic mechanisms involved in the production of dynamic gradients include increased contractility, decreased preload, and decreased afterload. In many patients with hypertrophic cardiomyopathy, the gradient is mid-ventricular and may be intensified by increased contractility, which exerts a direct muscular sphincter action. The stimuli that provoke or intensify left ventricular outflow tract gradients in hypertrophic cardiomyopathy generally improve myocardial performance in normal subjects and in patients with most other forms of heart disease. Conversely, reductions in contractility or increases in preload or afterload, which increased left ventricular dimensions, reduce or abolish the left ventricular outflow gradient.
    • One of the most potent stimuli for enhancing the left ventricular outflow gradient is postextrasystolic potentiation, which may occur after a spontaneous premature contraction or be induced by mechanical stimulation with a catheter.  The resultant increase in contractility in the beat after the extrasystole is so marked that it produces an increase in the outflow gradient. A characteristic change often occurs in the directly recorded arterial pressure tracing, which, in addition to displacing a more marked spike and dome configuration, exhibits a pulse pressure that fails to increase as expected or actually decreases (the so-called Brockenbrough-Braunwald phenomenon). This is one of the more reliable signs of dynamic obstruction of the left ventricular outflow tract. In some patients, the postextrasystolic murmur is attenuated despite an increase in the outflow gradient, apparently because, in this setting, the murmur mirrors to a greater degree changes in the severity of mitral regurgitation than changes in the outflow tract gradient.
    • Left ventriculography typically shows a hypertrophied ventricle and the presence of an outflow gradient. The anterior leaflet of the mitral valve moves anteriorly during systole and encroaches on the outflow tract. Associated with this motion is mitral regurgitation, which is a constant finding in patients with gradients.  The left ventricular cavity is often small, and systolic ejection is typically vigorous, resulting in virtual obliteration of the ventricular cavity at end systole.  In patients with apical involvement, the extensive hypertrophy may convey a spade-like configuration to the left ventricular angiogram.
    • In patients older than 45 years of age, obstructive coronary artery disease may be present, although the symptoms of ischemic pain are indistinguishable from those of patients with normal coronary angiograms and hypertrophic cardiomyopathy. The left anterior descending and septal perforator coronary arteries may demonstrate phasic narrowing and associated abnormalities of flow during systole
  • Electrophysiology studies
    • A diagnostic electrophysiology study using programmed electrical stimulation may identify conduction abnormalities, sinus node dysfunction (SND), and the potential for inducible arrhythmias.
    • The prognostic correlation of inducible arrhythmias with spontaneous clinical arrhythmias and/or sudden death is not entirely clear. Several studies have shown a relationship between electrophysiology results and risk stratification for sudden cardiac death, but other studies have not been able to demonstrate a direct relationship.

Histologic Findings

Myocardial hypertrophy and gross disorganization of the muscle bundles result in a characteristic whorled pattern; cell-to-cell disarray and disorganization of the myofibrillar architecture within a given cell occur in almost all patients with HCM. Fibrosis is prominent and may be extensive enough to produce grossly visible scars. Abnormal intramural coronary arteries, with a reduction in the size of the lumen and thickening of the vessel wall, are common in patients with HCM and occur in more than 80%. This abnormality most frequently occurs in the ventricular septum and accompanies extensive fibrosis in the affected walls of the heart.

More on Cardiomyopathy, Hypertrophic

Overview: Cardiomyopathy, Hypertrophic
Differential Diagnoses & Workup: Cardiomyopathy, Hypertrophic
Treatment & Medication: Cardiomyopathy, Hypertrophic
Follow-up: Cardiomyopathy, Hypertrophic
Multimedia: Cardiomyopathy, Hypertrophic
References
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Further Reading

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Keywords

hypertrophic cardiomyopathy, HCM, hypertrophic obstructive cardiomyopathy, idiopathic hypertrophic subaortic stenosis, IHSS, muscular subaortic stenosis, asymmetric septal hypertrophy, ASH, sudden death, sudden cardiac death, SCD, arrhythmogenic sudden death, myocardial hypertrophy, cardiomyopathy

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Contributor Information and Disclosures

Author

Michael E Zevitz, MD, Assistant Professor of Medicine, Finch University of the Health Sciences, The Chicago Medical School; Consulting Staff, Private Practice
Michael E Zevitz, MD is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Medical Association, and Michigan State Medical Society
Disclosure: Nothing to disclose.

Medical Editor

Gary E Sander, MD, PhD, Professor, Department of Internal Medicine, Division of Cardiology, Tulane University Health Sciences Center
Gary E Sander, MD, PhD is a member of the following medical societies: Alpha Omega Alpha, American College of Cardiology, American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, American Heart Association, American Society of Hypertension, Heart Failure Society of America, Louisiana State Medical Society, and Southern Society for Clinical Investigation
Disclosure: Nothing to disclose.

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Disclosure: eMedicine Salary Employment

Managing Editor

Frank M Sheridan, MD, Cardiology, Providence Everett Medical Center
Frank M Sheridan, MD is a member of the following medical societies: American College of Cardiology, American Heart Association, and Society for Cardiac Angiography and Interventions
Disclosure: Nothing to disclose.

CME Editor

Amer Suleman, MD, Consultant in Electrophysiology and Cardiovascular Medicine, Department of Internal Medicine, Division of Cardiology, Medical City Dallas Hospital
Amer Suleman, MD is a member of the following medical societies: American College of Physicians, American Heart Association, American Institute of Stress, American Society of Hypertension, Federation of American Societies for Experimental Biology, Royal Society of Medicine, and Society of Cardiac Angiography and Interventions
Disclosure: Nothing to disclose.

 
 
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