Impaired coronary circulation in patients with apical hypertrophic cardiomyopathy: noninvasive analysis by transthoracic Doppler echocardiography

[Vascular functional alterations in hypertrophic cardiomyopathy]

Hypertrophic cardiomyopathy is a hereditary, not uncommon cardiac disease, which is associated with asymmetric thickening and hypertrophy of the interventricular septum unrelated to hemodynamic reasons. Despite hypertrophic cardiomyopathy is considered to be a disorder of the heart muscle, several associated vascular alterations have been described. The aim of the present review is to summarize vascular functional alterations in hypertrophic cardiomyopathy.

Coronary flow reserve impairment in apical vs asymmetrical septal hypertrophic cardiomyopathy

BACKGROUND

Mechanisms underlying a reduction in coronary flow reserve (CFR) in hypertrophic cardiomyopathy (HCM), especially apical HCM (ApHCM), are elusive. This study set out to evaluate mechanisms underlying a reduction in CFR in 2 HCM subtypes.

HYPOTHESIS

Mechanisms for CFR reduction in HCM are different between the 2 subtypes of HCM.

METHODS

Thirty-one patients with asymmetrical septal hypertrophy (ASH), 43 with ApHCM, and 27 healthy volunteers were recruited. Mean diastolic coronary flow velocity (CFmv) was monitored before and after adenosine infusion by transthoracic echocardiography in the mid-to-distal left anterior descending coronary artery. Coronary flow reserve was defined as the ratio between CFmv before and after adenosine infusion. Left ventricular mass index and stress myocardial perfusion were assessed by cardiac magnetic resonance imaging.

RESULTS

Although basal CFmv was higher in ASH patients than in healthy controls (P<0.05), it was similar in ApHCM patients and controls (P=0.85). Poststress CFmv was significantly lower in both HCM subtypes than in controls (P<0.05). Consequently, CFR was higher in controls than in ASH or ApHCM patients (P<0.05). When HCM patients were stratified into 2 groups based on the presence of CFR impairment, no difference was observed between these 2 groups in terms of left ventricular mass index by cardiac magnetic resonance imaging. Multivariate logistic regression analysis identified basal CFmv as the only independent variable associated with CFR reduction in HCM (r2=0.49, P<0.001).

CONCLUSIONS

Whereas the inability to augment coronary flow to its maximal level during stress was found to underlie CFR impairment in both HCM subtypes, the recruitment of vasodilatory capacity at baseline was more prominent in ASH than in ApHCM patients.

Long-term prognostic value of coronary flow velocity reserve in patients with hypertrophic cardiomyopathy: 9-year follow-up results from SZEGED study

Reduction in coronary flow velocity reserve (CFR) is a recognized feature in hypertrophic cardiomyopathy (HCM). We sought to assess the long-term prognostic value of CFR by pulsed-wave Doppler transesophageal echocardiography (TEE) in HCM patients. The study comprised 20 patients with typical features of HCM. The patients were enrolled in 1999. All patients underwent a standard transthoracic echo-Doppler study to evaluate left ventricular function and a stress vasodilator TEE study to evaluate CFR. The success rate of follow-up was 18 out of 20 (90%). During a mean follow-up of 90 +/- 24 months, four patients suffered cardiovascular death (2 sudden cardiac deaths and 2 strokes). The other seven patients underwent invasive procedures (coronary angiography, implantable cardioverter defibrillator implantation, percutaneous transluminal septal myocardial ablation) or showed cerebrovascular events. Using receiver operator characteristic analysis, CFR < 2.35 was a significant predictor for cardiovascular event-free survival (sensitivity 91%, specificity 71%, area under the curve 74%, P = 0.05). Multivariable regression analysis showed that only CFR (hazard ratio (HR) 4.21, P < 0.05) was an independent predictor of cardiovascular event-free survival. Despite the relatively small number of patients involved in the study, results could suggest that CFR should be considered as an independent predictor for future cardiovascular events in HCM patients. However, further studies with larger HCM patient populations are warranted.

Proximal coronary hemodynamic changes evaluated by intracardiac echocardiography during myocardial ischemia and reperfusion in a canine model

BACKGROUND

The purpose of this study was to assess whether the dynamic changes in coronary flow velocity and coronary flow velocity reserve (CFVR) by intracardiac echocardiography (ICE) within proximal coronary arteries are related to myocardial perfusion status and infarct size in a myocardial ischemia-reperfusion injury model.

METHODS

In 14 dogs, left anterior descending coronary artery (LAD) was ligated for 2 hours followed by 2 hours reperfusion. Coronary flow velocity was obtained by ICE within coronary arteries at baseline, and at the end of both occlusion and reperfusion period. The CFVR was calculated as the ratio of hyperemic to resting peak diastolic velocity (PDV). Myocardial perfusion was evaluated by real time myocardial contrast echocardiography (MCE). The infarct area was detected by triphenyltetrazolium chloride (TTC) staining and expressed as the percentage of the whole left ventricular (LV) area.

RESULTS

CFVR significantly decreased both in proximal LAD and left circumflex (LCx) artery at the end of occlusion, and did not recover at the end of reperfusion. However, no significant difference in flow parameters was observed between dogs with myocardial perfusion defect and those without. CFVR in LAD at the end of reperfusion did not correlate with the infarct size (r =-0.182, P = NS) either.

CONCLUSIONS

Decreased CFVR detected by ICE occurs both in ischemic and in nonischemic proximal arteries during myocardial ischemia and early stage of reperfusion. This change in CFVR has poor correlation with the extent of microvascular impairment and cannot be used to predict infarct size.

Hypertrophic cardiomyopathy complicated by left ventricular apical necrosis and aneurysm in a young man: FDG-PET findings

A 29-year old male was transferred to our hospital with an abnormal chest X-ray finding diagnosed as hypertrophic cardiomyopathy with apical necrosis and aneurysm formation. Four years after the initial hospitalization, we confirmed the aneurysm and necrosis using both integrated positron emission tomography (PET) and computed tomography (CT) scanning. The F-18 2-fluoro-2-deoxy-D-glucose (FDG) PET/CT enabled precise localization of the aneurysm, which was found to be composed of semi-lunar calcification of non-metabolic myocardium. A contrast-enhanced CT angiography showed an hour-glass appearance of the left ventricular cavity. The integrated PET/CT fusion scanner is a novel multimodality technology that allows for a comprehensive analysis of the anatomical and functional status of complex heart disease. Based on these findings, long standing mechanical and physiologic abnormalities may have led to chronic ischemia in the hypertrophied myocardium, induced necrosis and calcification at the cardiac apex.