Why LV dilatation with vasodilator stress in hypertrophic cardiomyopathy?

Abstract

Transient ischemic dilatation (TID) of the left ventricle (LV) on vasodilator stress perfusion images is a concerning sign. In some, TID may reflect global subendocardial hypoperfusion during stress.1 A reduction in subendocardial perfusion results in an increase in observed chamber size on the stress images and the finding of TID. However, in patients with advanced coronary disease (CAD), TID during vasodilator stress might also reflect transient LV dysfunction due to generation of an actual myocardial oxygen supply/demand imbalance (true ischemia). TID on vasodilator stress PET perfusion images has previously been correlated with impaired myocardial perfusion reserve and with an acute decline in LV systolic function during stress.2 Moreover, patients with TID on vasodilator PET images exhibit poorer clinical outcomes as compared to those without TID who have similar LV ejection fractions and perfusion defect scores.3 Thus, TID on vasodilator stress images in CAD patients may reflect global subendocardial hypoperfusion, induction of a true oxygen supply/demand imbalance with ischemic LV dysfunction, or both. LV DILATATION IN HCMAcute LV dilatation on vasodilator stress images has also been observed in hypertrophic cardiomyopathy (HCM) patients, being reported in 55% of HCM patients without significant CAD. 4 However, the mechanism of LV dilatation in HCM patients has not been examined as fully as that in CAD patients. In this issue of the Journal, Bravo and co-authors correlate the findings on regadenoson stress 13 NH 3 perfusion studies and amyl nitrite augmented echocardiography to provide a more in-depth look at the potential mechanisms for TID in HCM patients. 5 In a retrospective analysis of 61 symptomatic HCM registry patients, they identified 32 individuals who exhibited TID during vasodilator stress PET perfusion imaging and 29 who did not. Both groups of patients were of similar age and gender composition and had similar medication use. The prevalence of diabetes, dyslipidemia, atrial fibrillation, hypertension, chest pain, dyspnea, syncope, sudden death, family history of HCM, and sudden death was also comparable in both groups.At the time of the PET perfusion studies, rest and stress heart rates, rest LV ejection fractions and rest and stress blood pressures were similar in both patient groups. Stress LV ejection fractions were significantly lower in the patients with TID than in those without TID (40 ± 9% vs 53 ± 9%, P \ .0001) and patients with TID exhibited greater declines in EF during stress (-17 ± 9% vs -3 ± 7%). HCM patients with TID had greater maximal LV wall thicknesses on echocardiography than those without TID (2.2 ± 0.5 vs 1.8 ± 0.3 cm, P \ .001) and in a statistical model including both continuous and categorical variables, the authors found that the only clear correlates of LV chamber dilatation were abnormal rest and hyperemic myocardial perfusion values and the degree of left ventricular hypertrophy. EARLY VS LATE TID RATIOSOne unique feature of the present study is that reformatted ...