Dipyridamole stress thallium-201 perfusion abnormalities in patients with hypertrophic cardiomyopathy. Relationship to clinical presentation and outcome.

Aims: Thallium-201 perfusion abnormalities are common in patients with hypertrophic cardiomyopathy and may be associated with an adverse prognosis in the young. The aim of this study was to prospectively determine the relationship between thallium-201 defects during dipyridamole stress to clinical presentation and outcome in a large consecutive series of patients with hypertrophic cardiomyopathy.

Methods/results: Thallium-201 single photon computed tomography was performed in 216 patients with hypertrophic cardiomyopathy during dipyridamole stress (0.5 mg. kg-1). Fixed perfusion defects occurred in 25%, and reversible defects in 22%. A combination of defects was present in 7%. Fixed defects were associated with: a history of syncope (17 of 46 with, vs 36 of 170 without syncope, P = 0.03); larger left ventricular end-diastolic (46.9 +/- 7.4 mm vs 43.3 +/- 6.4 mm; P = 0.001) and end-systolic dimension (30.2 +/- 8.4 mm vs 24.5 +/- 5.9 mm, P < 0.0001); increased left atrial diameter (46.1 +/- 8.1 mm vs 40.5 +/- 7.7 mm, P < 0.0001); lower fractional shortening (35.9 +/- 10.4% vs 43.8 +/- 8.6%, P < 0.0001): and lower maximal exercise oxygen consumption (24.2 +/- 8.1 ml. min-1. kg-1 vs 29.4 +/- 8.8 ml. min-1. kg-1, P < 0.0003). Reversible defects did not correlate with symptomatic status, but were associated with: larger left atrial dimensions (44.5 +/- 8.1 mm vs 41.0 +/- 8.0 mm; P = 0.009) and greater maximal left ventricular wall thickness (24.0 +/- 7.0 mm vs 20.6 +/- 7.0 mm, P = 0.003). The mean follow up time was 41 +/- 21 months, range 0.6-124. There was no association between any thallium-201 abnormality and disease related death in young or adult patients.

Conclusion: The present study shows that fixed thallium-201 perfusion defects detected during dipyridamole stress in patients with hypertrophic cardiomyopathy are associated with syncope, larger left ventricular cavity dimensions and reduced exercise capacity. Although the event rate was relatively small, there was no evidence for an association between thallium-201 defects and survival.