Frequency and severity of myocardial perfusion abnormalities using Tc-99m MIBI SPECT in cardiac syndrome X

BACKGROUND: Cardiac syndrome X is defined by a typical angina pectoris with normal or near normal (stenosis <40%) coronary angiogram with or without electrocardiogram (ECG) change or atypical angina pectoris with normal or near normal coronary angiogram plus a positive none-invasive test (exercise tolerance test or myocardial perfusion scan) with or without ECG change. Studies with myocardial perfusion imaging on this syndrome have indicated some abnormal perfusion scan. We evaluated the role of myocardial perfusion imaging (MPI) and also the severity and extent of perfusion abnormality using Tc-99m MIBI Single Photon Emission Computed Tomography (SPECT) in these patients. METHODS: The study group consisted of 36 patients with cardiac syndrome X. The semiquantitative perfusion analysis was performed using exercise Tc-99m MIBI SPECT. The MPI results were analyzed by the number, location and severity of perfusion defects. RESULTS: Abnormal perfusion defects were detected in 13 (36.10%) cases, while the remaining 23 (63.90%) had normal cardiac imaging. Five of 13 (38.4%) abnormal studies showed multiple perfusion defects. The defects were localized in the apex in 3, apical segments in 4, midventricular segments in 12 and basal segments in 6 cases. Fourteen (56%) of all abnormal segments revealed mild, 7(28%) moderate and 4 (16%) severe reduction of tracer uptake. No fixed defects were identified. The vessel territories were approximately the same in all subjects. The Exercise treadmill test (ETT) was positive in 25(69%) and negative in 11(30%) patients. There was no consistent pattern as related to the extent of MPI defects or exercise test results. CONCLUSION: Our study suggests that multiple perfusion abnormalities with different levels of severity are common in cardiac syndrome X, with more than 30 % of these patients having at least one abnormal perfusion segment. Our findings suggest that in these patients microvascular angina is probably more common than is generally believed

Determinants of myocardial energetics and efficiency in symptomatic hypertrophic cardiomyopathy

Next to hypertrophy, hypertrophic cardiomyopathy (HCM) is characterized by alterations in myocardial energetics. A small number of studies have shown that myocardial external efficiency (MEE), defined by external work (EW) in relation to myocardial oxidative metabolism (MVO2), is reduced. The present study was conducted to identify determinants of MEE in patients with HCM by use of dynamic positron emission tomography (PET) and cardiovascular magnetic resonance imaging (CMR). Twenty patients with HCM (12 men, mean age: 55.2 +/- 13.9 years) and 11 healthy controls (7 men, mean age: 48.1 +/- 10 years) were studied with [C-11]acetate PET to assess MVO2. CMR was performed to determine left ventricular (LV) volumes and mass (LVM). Univariate and multivariate analyses were employed to determine independent predictors of myocardial efficiency. Between study groups, MVO2 (controls: 0.12 +/- 0.04 ml center dot min(-1)center dot g(-1), HCM: 0.13 +/- 0.05 ml center dot min(-1)center dot g(-1), p = 0.64) and EW (controls: 9,139 +/- 2,484 mmHg center dot ml, HCM: 9,368 +/- 2,907 mmHg center dot ml, p = 0.83) were comparable, whereas LVM was significantly higher (controls: 99 +/- 21 g, HCM: 200 +/- 76 g, p < 0.001) and MEE was decreased in HCM patients (controls: 35 +/- 8%, HCM: 21 +/- 10%, p < 0.001). MEE was related to stroke volume (SV), LV outflow tract gradient, NH2-terminal pro-brain natriuretic peptide (NT-proBNP) and serum free fatty acid levels (all p < 0.05). Multivariate analysis revealed that SV ( = 0.74, p < 0.001) and LVM ( = -0.43, p = 0.013) were independently related to MEE. HCM is characterized by unaltered MVO2, impaired EW generation per gram of myocardial tissue and subsequent deteriorated myocardial efficiency. Mechanical external efficiency could independently be predicted by SV and LVM

Epidemiology of cardiac syndrome X and microvascular angina

Chest pain and normal coronary angiography is seen in up 30 % of patients undergoing the investigation. Despite its notable prevalence, the epidemiology of the condition remains poorly documented. Since the turn of the twentieth century, researchers have been baffled by “unmistakable” angina in the absence of coronary artery disease. Curiosity as to the cardiac aetiology of this chest pain became the focus of several key studies investigating the clinical and haemodynamic features of patients with normal coronary angiography. From these early findings, the cardinal features of three specific disorders associated with normal coronary angiography were established – Cardiac Syndrome X, Microvascular Angina and more recently, the Coronary Slow Flow Phenomenon. Although ambiguity in the literature exists, it is likely that an ‘ischemic’ mechanism for the chest pain in these patients is explained by coronary microvascular dysfunction. It also now understood that despite the absence of significant coronary artery disease, the outcomes of patients are not entirely favourable, with studies suggesting a frequent persistence of chest pain, and increased risk of cardiac events, particularly among women. This chapter will review the available epidemiological data on patients with chest pain and normal coronary angiography, and the clinical features and possible aetiological explanations for the specific coronary microvascular disorders.Rosanna Tavella and Guy D. Eslic