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Myocardial perfusion abnormalities in patients with hypertrophic cardiomyopathy: assessment with thallium-201
P T O'Gara1, R O Bonow, B J Maron
1Cardiology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD 20892.
Insights
Myocardial ischemia is common in hypertrophic cardiomyopathy (HCM). Abnormalities in thallium-201 scans indicate scar or ischemia, often linked to reduced heart function, while reversible defects suggest dynamic ischemia in patients with normal function.
Area of Science:
- Cardiology
- Nuclear Cardiology
- Cardiovascular Imaging
Background:
- Myocardial ischemia is implicated in hypertrophic cardiomyopathy (HCM) presentation and progression.
- Understanding perfusion abnormalities is crucial for managing HCM patients across the clinical spectrum.
Purpose of the Study:
- To determine the prevalence and functional significance of myocardial perfusion abnormalities in a diverse group of hypertrophic cardiomyopathy patients.
- To correlate perfusion defects with left ventricular systolic function and wall thickness.
Main Methods:
- Studied 72 hypertrophic cardiomyopathy patients (12-69 years) using thallium-201 emission computed tomography.
- Performed imaging immediately after maximal exercise and after a 3-hour delay to assess perfusion defects.
- Analyzed regional perfusion defects, reversibility, left ventricular ejection fraction, and wall thickness.
Main Results:
- 57% of patients (41/72) showed perfusion defects.
- Fixed defects, suggesting scar/severe ischemia, were linked to impaired systolic function (ejection fraction <50%).
- Reversible defects, indicating dynamic ischemia, were prevalent in patients with normal or hyperdynamic systolic function (ejection fraction ≥50%).
Conclusions:
- Myocardial perfusion abnormalities are common in hypertrophic cardiomyopathy.
- Fixed defects correlate with reduced systolic function, while reversible defects are associated with preserved systolic function.
- Dynamic ischemic processes may significantly impact the clinical course of hypertrophic cardiomyopathy.
Abstract:
Myocardial ischemia may play a critical role in the symptomatic presentation and natural history of hypertrophic cardiomyopathy (HCM). To assess the relative prevalence and functional significance of myocardial perfusion abnormalities in patients comprising the broad clinical spectrum of HCM, we studied 72 patients (ages 12 to 69 years, mean 40) using thallium-201 emission computed tomography. Imaging was performed immediately after maximal exercise and again after a 3 hr delay. Regional perfusion defects were identified in 41 of the 72 patients (57%). Fixed or only partially reversible defects were evident in 17 patients, 14 of whom (82%) had left ventricular ejection fractions of less than 50% at rest. Twenty-four patients demonstrated perfusion defects during exercise that completely reversed at rest; all had normal or hyperdynamic left ventricular systolic function (ejection fraction greater than or equal to 50%). Perfusion abnormalities were present in all regions of the left ventricle. However, the fixed defects were observed predominantly in segments of the left ventricular wall that were of normal or only mildly increased (15 to 20 mm) thickness; in contrast, a substantial proportion (41%) of the completely reversible defects occurred in areas of moderate-to-marked wall thickness (greater than or equal to 20 mm, p less than .001). Neither a history of chest pain nor its provocation with treadmill exercise was predictive of an abnormal thallium study, since regional perfusion defects were present in 10 of 18 (56%) completely asymptomatic patients, compared with 31 of 54 (58%) symptomatic patients. These data indicate that myocardial perfusion abnormalities occur commonly among patients with HCM. Fixed or only partially reversible defects suggestive of myocardial scar and/or severe ischemia occur primarily in patients with impaired systolic performance. Completely reversible perfusion abnormalities occur predominantly in patients with normal or supranormal left ventricular systolic function. Such dynamic changes in regional thallium activity may reflect an ischemic process that contributes importantly to the clinical manifestations and natural history of HCM.