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Evidence for a systemic defect of resistance-sized arterioles in hypertrophic cardiomyopathy
R Pedrinelli1, M Spessot, G Chiriatti
1I Clinica Medica, University of Pisa, Italy.
Insights
Patients with hypertrophic cardiomyopathy (HCM) show impaired forearm and coronary vasodilator reserve, indicating a generalized arteriolar abnormality. This finding suggests a potential mechanism contributing to HCM
Area of Science:
- Cardiovascular Physiology
- Vascular Biology
- Cardiology
Background:
- Hypertrophic cardiomyopathy (HCM) is associated with coronary arteriolar abnormalities.
- It remains unclear if these abnormalities are specific to the coronary vasculature or represent a generalized phenomenon.
Purpose of the Study:
- To investigate generalized arteriolar dysfunction in patients with HCM.
- To compare forearm and coronary vasodilator reserve in HCM patients and controls.
Main Methods:
- Forearm vasodilator reserve was assessed by measuring minimal forearm vascular resistance (Rmin) during reactive hyperemia.
- Coronary vasodilator reserve was quantified using 13N-ammonia positron emission tomography to measure left ventricular blood flow and coronary resistance before and after dipyridamole infusion.
- Forearm and coronary resistance measurements were compared between 12 HCM patients and age-/sex-matched controls.
Main Results:
- Patients with HCM exhibited significantly higher Rmin compared to controls, indicating impaired forearm vasodilator reserve.
- Coronary vasodilator reserve, assessed by the change in coronary resistance after dipyridamole, was significantly related to Rmin.
- No correlation was observed between coronary resistance changes and septal thickness in HCM patients.
Conclusions:
- Systemic and coronary arterioles are affected by an abnormality in patients with HCM, independent of cardiac hypertrophy.
- This generalized arteriolar dysfunction may play a role in the clinical progression of hypertrophic cardiomyopathy.
Background:
To investigate whether the abnormalities of coronary arterioles observed in association with hypertrophic cardiomyopathy represent a generalized phenomenon, both forearm and coronary vasodilator reserve were measured in 12 patients with hypertrophic cardiomyopathy.
Methods:
Forearm vasodilator reserve was evaluated by measuring minimal forearm vascular resistance (Rmin, the ratio of mean intra-arterial pressure to peak forearm blood flow measured by venous plethysmography) under conditions of maximal postocclusive reactive hyperemia.
Results:
In a subgroup (n = 5) of patients, the intra-arterial infusion of sodium nitroprusside combined with arterial occlusion did not produce additional vasodilation, indicating that the ischemic stimulus was indeed maximal. Coronary reserve was quantitated by measuring left ventricular blood flow (13N-ammonia and positron emission tomography) and coronary resistance at baseline and after intravenous dipyridamole (0.56 mg/kg). Rmin was significantly greater in patients than in a group of age- and sex-matched controls. The percentage change in coronary resistance after dipyridamole was significantly related to Rmin, whereas no correlation was found between change in coronary resistance and individual septal thickness values.
Conclusions:
Independent of cardiac hypertrophy, systemic and coronary arterioles of patients with hypertrophic cardiomyopathy are affected by an abnormality that may contribute to the clinical evolution of this syndrome.