Transmural myocardial blood flow distribution in hypertrophic cardiomyopathy and effect of treatment

Abstract

Verapamil alleviates symptoms in patients with hypertrophic cardiomyopathy (HCM), but the underlying mechanism of improvement remains speculative. Baseline and dipyridamole myocardial blood flow (MBF) were measured in 15 HCM patients (14 men, 42 +/- 10 years), before and after 4 weeks of verapamil SR 480 mg daily, using 15O labelled water the positron emission tomography (PET). Subendocardial (endo) and subepicardial (epi) MBF was measured in the septum (thickness 25.4 +/- 5.8 mm). Pre-treatment baseline whole heart MBF was 1.02 +/- 0.28 ml/min/g and 1.01 +/- 0.30 ml/min/g on treatment (p = ns). Dipyridamole MBF was 1.39 +/- 0.31 ml/min/g off treatment and 1.23 +/- 0.34 ml/min/g on treatment (p = ns). Coronary flow reserve (dipyridamole/resting MBF) was 1.45 +/- 0.52 and 1.30 +/- 0.51, respectively (p = ns). At baseline, the septal endo/epi MBF ratio was uniform off and on treatment (1.13 +/- 0.18 vs 1.18 +/- 0.21, p = ns). Before treatment, the endo/epi ratio following dipyridamole decreased to 0.93 +/- 0.24 (p < 0.01 vs baseline) and 5/15 (33%) patients had a ratio < 0.8 which would suggest subendocardial underperfusion. During treatment, the endo/epi ratio following dipyridamole was no more different from baseline (1.06 +/- 0.24, p = ns vs baseline) and 2/14 (14%) patients had an endo/epi < 0.8. PET can be successfully used to determine transmural MBF in vivo in patients with hypertrophied ventricles. Despite symptomatic improvement, high dose verapamil therapy does not increase total MBF in patients with HCM but may improve septal transmural MBF distribution during dipyridamole in some patients.

New frontiers for cardiac PET: looking beyond mean transmural myocardial quantification

“…15 O) with cardiac positron emission tomography (PET) to split mean transmural myocardial perfusion into two layers (subendocardial and subepicardial) and conducted in patients having normal or increased left ventricular (LV) myocardial wall thickness: HCM, coronary artery disease (CAD), aortic stenosis and healthy controls [2][3][4][5][6]. The study by Sciagrà et al is of particular interest because it broadens the scope of application of cardiac PET to the use of a more widely available myocardial perfusion PET radiotracer 13 NH 3 for splitting mean transmural absolute myocardial wall perfusion into subendocardial and subepicardial components.…”

Disminución de la reserva de flujo coronario en pacientes con insuficiencia cardíaca no isquémica

“…Rev Esp Cardiol 2003;56(4):354-60 355 miocardiopatía hipertrófica 5 o dilatada 6,7 , y en la hipertrofia secundaria a lesiones valvulares 8 . La RFC se ha encontrado alterada en la insuficiencia cardíaca experimental 9 .…”

Validation of pixel-wise parametric mapping of myocardial blood flow with 13NH3 PET in patients with hypertrophic cardiomyopathy

“…Water labelled with 15 O has been considered ideal for MBF quantitation [5][6][7][8][9][10]. More recently, differential evaluation of subendocardial and subepicardial MBF has been attempted using H 2 15 O MBF parametric images [11][12][13][14]. Identification of transmural abnormalities in MBF could play an important role in the evaluation of various heart diseases, and represents a major advance in the current practice of quantitative PET [15].…”

“…We focused on patients with hypertrophic cardiomyopathy (HCM), whose left ventricular (LV) wall thickness can be more than 20 mm and therefore well above the resolution limits of modern PET scanners [19]. Because subendocardial ischaemia has been demonstrated in these patients, they represent the ideal population to assess the ability of parametric 13 NH 3 MBF images to reveal transmural abnormalities [11,19,20]. Thus, the aim of the study was to assess the ability of 13 NH 3 to reveal transmural abnormalities in MBF already demonstrated in patients with HCM using H 2 15 O [12].…”