Assessment of Coronary Flow with Transthoracic Color Doppler Echocardiography in Patients with Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy-Septal Perforator Arteries Doppler Flow Dynamics

BACKGROUND

Patients with hypertrophic cardiomyopathy (HCM) have been shown to exhibit abnormal diastolic vessel flow; however, flow pattern profiles and their possible association with different grades of diastolic dysfunction have not been studied. Color Doppler two-dimensional echocardiography permits visualization of the septal perforator arteries, and pulsed-wave Doppler allows recording of diastolic septal artery flow (SAF). Through routine visualization of the septal perforator arteries and acquisition of SAF, we noticed 3 patterns of SAF in patients with HCM. In this study, we aimed to assess the feasibility of the acquisition of SAF and to describe types of SAF in an HCM cohort and their associations with diastolic function.

METHODS

We reviewed two-dimensional echocardiograms and the electronic records of 108 patients with HCM in whom septal artery color and spectral Doppler had been performed. The peak diastolic and end-diastolic velocities, diastolic slope, diastolic flow time-velocity integral, and systolic flow reversal of the septal perforator arteries were recorded with pulsed-wave Doppler. Echocardiographic and clinical characteristics were analyzed.

RESULTS

A reproducible pulsed-wave Doppler tracing was recorded in 54% of patients with HCM. Three distinct patterns of SAF were identified: type 1-smooth, linear holodiastolic velocity decrease; type 2-with presence of an atrial dip; and type 3-biphasic velocity decrease with an early, rapid diastolic slope and a mid-to-late gentle slope. These 3 SAFs correlated with different grades of diastolic dysfunction.

CONCLUSION

Septal artery flow could be detected in more than 50% of patients with HCM. Three distinct types of SAF were identified, correlating with different grades of diastolic dysfunction. These 3 types of SAF can provide additional information about left ventricular end-diastolic pressure and diastolic function in patients with HCM in whom diastolic function may be difficult to determine.

Microvascular Dysfunction in Hypertrophic Cardiomyopathy

Myocardial ischemia is an established pathophysiological feature of hypertrophic cardiomyopathy (HCM) that impacts various clinical features, including heart failure (HF) and sudden cardiac death (SCD). The major determinant of myocardial ischemia in HCM is coronary microvascular dysfunction (CMD) in the absence of epicardial coronary artery abnormalities. Despite the impossibility to directly visualize microcirculation in vivo, a multimodality approach can allow a detailed assessment of microvascular dysfunction and ischemia. Accordingly, the non-invasive assessment of CMD using transthoracic Doppler echocardiography, positron emission tomography, and cardiac magnetic resonance should now be considered mandatory in any HCM patient. Noteworthy, a complete diagnostic work-up for myocardial ischemia plays a major role in the approach of the patients with HCM and their risk stratification. Chronic and recurrent episodes of ischemia can contribute to fibrosis, culminating in LV remodeling and HF. Ischemia can potentially constitute an arrhythmic substrate and might prove to have an added value in risk stratification for SCD. Accordingly, strategies for the early diagnosis of CMD should now be considered an important challenge for the scientific community.

Coronary microvascular dysfunction in hypertrophic cardiomyopathy: Pathophysiology, assessment, and clinical impact

Myocardial ischemia constitutes one of the most important pathophysiological features in hypertrophic cardiomyopathy. Chronic and recurrent myocardial ischemia leads to fibrosis, which may culminate in myocardial dysfunction. Since the direct visualization of coronary microcirculation in vivo is not possible, its function must be studied indirectly. Invasive and noninvasive techniques allow microcirculatory dysfunction to be evaluated, including echocardiography, magnetic resonance, positron emission tomography, and cardiac catheterization. Blunted myocardial blood flow and coronary flow reserve have been suggested to associate with unfavorable prognosis. Microcirculatory dysfunction may be one additional important parameter to take into account for risk stratification beyond the conventional risk factors.

Noninvasive study of coronary microcirculation response to a cold pressor test

BACKGROUND

The aims of this study were to noninvasively (i) assess the coronary microcirculation changes in response to a cold pressor test (CPT) in control subjects, nondiabetic obese patients and patients with type 2 diabetes and (ii) investigate the response of the coronary microcirculation in patients with diabetes according to the presence or the absence of silent myocardial ischaemia (SMI), asymptomatic coronary stenosis (CS) and left ventricle hypertrophy (LVH).

METHODS

The mean left anterior descending coronary flow velocity (mCFV) was measured using transthoracic Doppler before and after a CPT in 16 control subjects, 11 obese and 66 asymptomatic diabetic patients with a high cardiovascular risk. Patients with diabetes were screened for SMI using stress myocardial scintigraphy and/or echocardiography. A coronary angiography was performed in those with SMI.

RESULTS

At baseline, pressure-rate product (PRP) was correlated with mCFV (r = 0.23; P < 0.05) and left ventricle mass (r = 0.26; P < 0.05) in the whole population. Changes in PRP and mCFV during CPT were correlated with controls (r = 0.58, P < 0.05), obese (r = 0.75, P < 0.01) and diabetic patients without CS (r = 0.56, P < 0.0001) or without LVH (r = 0.63, P < 0.05) but not in diabetic patients with CS or with LVH. In patients with diabetes, SMI was associated with mCFV changes, independent of other parameters (P < 0.05).

CONCLUSION

Transthoracic coronary Doppler allows noninvasive study of changes in the coronary microcirculation during CPT. In asymptomatic patients with type 2 diabetes, this method showed that SMI was associated with mCFV changes during CPT and the presence of CS or LVH was associated with a mismatch between coronary microcirculation and myocardial oxygen demand.