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

L Choudhury1, P Elliott, O Rimoldi

  • 1MRC Cyclotron Unit, Imperial College School of Medicine, Hammersmith Hospital, London, United Kingdom.

Basic Research in Cardiology
|March 31, 1999
PubMed

Insights

Verapamil therapy for hypertrophic cardiomyopathy (HCM) patients did not increase overall myocardial blood flow (MBF). However, it improved septal blood flow distribution during stress in some individuals, suggesting a potential benefit beyond total flow.

Area of Science:

  • Cardiology
  • Nuclear Medicine
  • Pharmacology

Background:

  • Hypertrophic cardiomyopathy (HCM) is a condition affecting the heart muscle.
  • Verapamil is used to manage HCM symptoms, but its mechanism of action is not fully understood.
  • Assessing myocardial blood flow (MBF) is crucial for understanding heart function in HCM.

Purpose of the Study:

  • To investigate the effect of verapamil on myocardial blood flow (MBF) in patients with hypertrophic cardiomyopathy (HCM).
  • To determine if verapamil improves blood flow distribution within the heart septum.
  • To explore the underlying mechanisms of verapamil's symptomatic relief in HCM.

Main Methods:

  • 15 HCM patients underwent positron emission tomography (PET) scans using 15O-labeled water.
  • Myocardial blood flow (MBF) was measured at rest and during dipyridamole stress, before and after 4 weeks of verapamil SR (480 mg daily).
  • Transmural flow was assessed by measuring subendocardial and subepicardial MBF in the septum.

Main Results:

  • Verapamil treatment did not significantly alter resting or dipyridamole-induced whole-heart MBF.
  • Coronary flow reserve remained unchanged after verapamil therapy.
  • While baseline septal endocardial/epicardial MBF ratio was uniform, dipyridamole stress revealed potential subendocardial underperfusion in some patients before treatment.
  • Verapamil treatment improved the septal endocardial/epicardial MBF ratio during dipyridamole stress in some patients, reducing the incidence of subendocardial underperfusion.

Conclusions:

  • High-dose verapamil therapy does not increase total myocardial blood flow (MBF) in HCM patients.
  • Verapamil may improve regional septal transmural MBF distribution during pharmacologic stress in a subset of HCM patients.
  • Positron emission tomography (PET) is a viable tool for assessing transmural MBF in hypertrophied ventricles.

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