Reversal of inappropriate peripheral vascular responses in hypertrophic cardiomyopathy

Area of Science:

• Cardiology
• Autonomic Nervous System Research
• Pharmacology

Background:

• Some hypertrophic cardiomyopathy (HCM) patients exhibit abnormal blood pressure response (ABPR) to exercise, potentially due to paradoxical peripheral vasodilation.
• Central volume unloading via lower body negative pressure (LBNP) reveals similar paradoxical forearm vasodilation in a subset of HCM patients.
• These abnormal reflexes may stem from left ventricular mechanoreceptor activation, a mechanism potentially implicated in vasovagal syncope.

Purpose of the Study:

• To determine the frequency of abnormal forearm vasodilator responses during LBNP in HCM patients with ABPR during exercise.
• To evaluate the efficacy of propranolol, clonidine, and paroxetine in treating these abnormal vascular responses and exercise blood pressure issues.

Main Methods:

• Assessed blood pressure changes during exercise.
• Utilized plethysmography to measure forearm vascular responses and baroreceptor sensitivity during LBNP.
• Conducted a double-blind crossover study involving 21 non-obstructive HCM patients with ABPR.

Main Results:

• 43% of patients (group A) displayed paradoxical vasodilator responses during LBNP, while 57% (group B) showed normal vasoconstrictor responses.
• Paroxetine improved systolic blood pressure (SBP) during exercise in group A and reversed paradoxical LBNP responses in 78% of these patients.
• Propranolol and clonidine demonstrated efficacy in reversing paradoxical vascular responses in some patients from group A.

Conclusions:

• Paradoxical forearm vasodilatation during LBNP is observed in approximately 40% of HCM patients with exercise-induced ABPR.
• Propranolol, clonidine, and paroxetine effectively reversed these abnormal vasodilatory responses.
• Paroxetine demonstrated an additional benefit by improving the SBP response to exercise in affected patients.