Hypertrophic cardiomyopathy other diagnostic studies

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Soroush Seifirad, M.D.[2]

Overview

Left heart catheterization can be a useful diagnostic study to ascertain the severity of the dynamic outflow obstruction and its location. Among patients who have chest discomfort or an anginal equivalent, coronary angiography carries a class I recommendation to evaluate for the presence of obstructive coronary artery disease.The prognostic value of electrophysiologic testing of patients with HOCM in the absence of spontaneous, sustained ventricular tachycardia is limited, and in fact, the study itself may be dangerous. Paced electrogram fractionation in hypertrophic cardiomyopathy may helpful in determining which patients are at risk for ventricular fibrillation.

Cardiac Cathetererization

Left heart catheterization can be a useful diagnostic study to ascertain the severity of the dynamic outflow obstruction and its location.

Left Heart Catheterization

Upon cardiac catheterization, catheters can be placed in the left ventricle and the ascending aorta, to measure the pressure difference between these structures. In normal individuals, during ventricular systole, the pressure in the ascending aorta and the left ventricle will equalize, and the aortic valve is open. In individuals with aortic stenosis or with HCM with an outflow tract gradient, there will be a pressure gradient (difference) between the left ventricle and the aorta, with the left ventricular pressure higher than the aortic pressure. This gradient represents the degree of obstruction that has to be overcome in order to eject blood from the left ventricle.

The Brockenbrough–Braunwald–Morrow sign is observed in individuals with HCM with outflow tract gradient. This sign can be used to differentiate HCM from aortic stenosis. In individuals with aortic stenosis, after a premature ventricular contraction (PVC), the following ventricular contraction will be more forceful, and the pressure generated in the left ventricle will be higher. Because of the fixed obstruction that the stenotic aortic valve represents, the post-PVC ascending aortic pressure will increase as well. In individuals with HCM, however, the degree of obstruction will increase more than the force of contraction will increase in the post-PVC beat. The result of this is that the left ventricular pressure increases and the ascending aortic pressure decreases, with an increase in the LVOT gradient.

Pressure tracings demonstrating the Brockenbrough–Braunwald–Morrow sign
AO = Descending aorta; LV = Left ventricle; ECG = Electrocardiogram.
After the third QRS complex, the ventricle has more time to fill. Since there is more time to fill, the left ventricle will have more volume at the end of diastole (increased preload). Due to the Frank–Starling law of the heart, the contraction of the left ventricle (and pressure generated by the left ventricle) will be greater on the subsequent beat (beat #4 in this picture). Because of the dynamic nature of the outflow obstruction in HCM, the obstruction increases more that the left ventricular pressure increase. This causes a fall in the aortic pressure as the left ventricular pressure rises (seen as the yellow shaded area in the picture).

While the Brockenbrough–Braunwald–Morrow sign is most dramatically demonstrated using simultaneous intra-cardiac and intra-aortic catheters, it can be seen on routine physical examination as a decrease in the pulse pressure in the post-PVC beat in individuals with HCM.

Coronary Angiography

Among patients who have chest discomfort or an anginal equivalent, coronary angiography carries a class I recommendation to evaluate for the presence of obstructive coronary artery disease.

Detection of Concomitant Coronary Disease (DO NOT EDIT)

Class I

"1. Coronary arteriography (invasive or computed tomographic imaging) is indicated in patients with HCM with chest discomfort who have an intermediate to high likelihood of CAD when the identification of concomitant CAD will change management strategies. (Level of Evidence: C) "

Stress Test

Stress testing can be used to assess a hypertrophic obstructive cardiomyopathy patient's functional capacity and response to therapy, their risk of sudden cardiac death, and the magnitude of dynamic outflow obstruction on stress echocardiography.

2011 ACCF/AHA Guideline for the Diagnosis and Treatment of Hypertrophic Cardiomyopathy (DO NOT EDIT)

Stress Testing (DO NOT EDIT)

Class IIa

"1. Treadmill exercise testing is reasonable to determine functional capacity and response to therapy in patients with HCM. (Level of Evidence: C) "

"2. Treadmill testing with monitoring of an ECG and blood pressure is reasonable for SCD risk stratification in patients with HCM. (Level of Evidence: B) "

"3. In patients with HCM who do not have a resting peak instantaneous gradient of greater than or equal to 50 mm Hg, exercise echocardiography is reasonable for the detection and quantification of exercise-induced dynamic LVOT obstruction. (Level of Evidence: B) "

Electrophysiologic Stress Test

The prognostic value of electrophysiologic testing of patients with HOCM in the absence of spontaneous, sustained ventricular tachycardia is limited, and in fact, the study itself may be dangerous. Sustained ventricular tachyarrhythmias, predominantly rapid polymorphic ventricular tachycardia, have been induced in 27 to 43 percent of patients with HOCM at electrophysiologic study, but their prognostic significance is controversial. The predictive value of asymptomatic nonsustained ventricular tachycardia is also limited. Paced electrogram fractionation in hypertrophic cardiomyopathy may helpful in determining which patients are at risk for ventricular fibrillation.

The absence of inducible, sustained monomorphic ventricular tachyarrhythmias, absence of nonsustained ventricular tachycardia on ambulatory ECG, and no history of impaired consciousness (i.e., cardiac arrest or syncope) identified a subset (22 percent) of patients with HCM with a low (<1 percent) risk for sudden cardiac death.