A unique perfusion pattern with 15O-water PET as a risk marker for arrhythmias in hypertrophic cardiomyopathy

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Swedish Heart Lung Foundation. Background Myocardial ischemia in hypertrophic cardiomyopathy (HCM) is associated with an elevated risk of ventricular arrhythmia and sudden cardiac death. Fibrosis often occurs in subendocardial regions of the LV and the RV insertion in the interventricular septum. Globally lowered hyperemic myocardial blood flow (MBF) by 15O-water PET is known to indicate poor prognosis, but is mainly linked to late-stage "burn-out". Recent scanner and image analysis developments allow detailed 3D visualisation of quantitative biventricular 15O-water MBF. Purpose To investigate whether there is a visual myocardial perfusion pattern with 15O-water PET in patients with HCM which could indicate an increased risk of arrhythmias. Methods We reanalysed rest/adenosine stress 15O-water PET in 24 patients with high-risk HCM treated with implantable cardioverter-defibrillator from a previous study. Non-sustained ventricular tachycardia (NSVT) was noted in 10 patients during 1 year preceding PET. PET was used to determine the LV MBF subendocardial-subepicardial gradient (ml/g/min per mm). Parametric MBF images from 15O-water PET at rest and stress were visually analysed at a segmental level. The myocardial segment which visually had both the highest endocardial MBF at rest and the lowest endocardial MBF at stress was selected as the most affected segment for each patient. Results Reduced resting MBF with partial normalisation at stress was seen in the RV insertion in 15 patients, including all NSVT subjects. Sixteen patients, including all NSVT subjects, had a visual perfusion pattern in the septal wall or apex with enhanced subendocardial MBF at rest and reduced MBF at stress in the same segment. The MBF gradient at stress was 0.04±0.01 ml/g/min per mm for the patients with NSVT and 0.07±0.03 ml/g/min per mm for the patients without NSVT in the visually most affected segments (p = 0.01). Conclusions Using 3D visualisation of quantitative MBF we noted a distinct pattern with intramural redistribution of perfusion between rest and stress in HCM, significantly associated with NSVT. Reduced resting perfusion at RV insertion points has not been reported in other cardiomyopathies. Enhanced subendocardial resting perfusion in ischemic segments might indicate reactive postischemic hyperemia. Clinical use of 15O-water PET to predict ventricular arrhythmia requires prospective trials.