title: Vagal enhancement due to subendocardial ischemia as a cause of abnormal blood pressure response in hypertrophic cardiomyopathy.
abstract: BACKGROUND
  Patients with hypertrophic cardiomyopathy (HCM) often develop myocardial ischemia in association with abnormal blood pressure response to exercise. Vagal nerves mediate cardioinhibitory stimuli, with little knowledge regarding vagal response to myocardial ischemia in patients with HCM.
  
  
  METHODS
  Exercise Tc-99m-tetrofosmin myocardial scintigraphy was performed in 59 HCM patients and 39 controls who had no evidence of cardiac disease. We examined how reversible regional perfusion abnormality and transient left ventricular cavity dilation, a parameter of subendocardial ischemia, are related to vagal modulation as assessed by coefficient of high frequency component variance (CCV(HF)) on heart rate variability. We then correlated the results with abnormal blood pressure response to exercise, defined as failed increase >or=25 mm Hg during exercise.
  
  
  RESULTS
  Regional perfusion abnormality and left ventricular cavity dilation were observed in 26 and 21 HCM patients, respectively. The percentage change of CCV(HF) from before to after exercise was higher in HCM patients with left ventricular cavity dilation than without or controls (5.2+/-9.8%, -23.5+/-5.7%, -14.5+/-5.5%, P=0.004). By contrast, the change of CCV(HF) was similar in HCM patients with regional perfusion abnormality, those without, and controls. The change of CCV(HF) was correlated with exercise-induced increase in systolic blood pressure (rho=-0.64, P<0.001); HCM patients with abnormal blood pressure response were characterized by a higher percentage change in CCV(HF) (50.0+/-18.3%).
  
  
  CONCLUSIONS
  Subendocardial ischemia provoked vagal enhancement in patients with HCM, which may be related to the development of abnormal blood pressure response to exercise.
authors.affiliation: Department of Cardiology, Matsushita Memorial Hospital, Osaka, Japan. js-k@wf6.so-net.ne.jp
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kawasaki
authors.forename: Akihiro
authors.initials: A
authors.lastname: Azuma
authors.forename: Toshiro
authors.initials: T
authors.lastname: Kuribayashi
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Akakabe
authors.forename: Michiyo
authors.initials: M
authors.lastname: Yamano
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Miki
authors.forename: Takahisa
authors.initials: T
authors.lastname: Sawada
authors.forename: Tadaaki
authors.initials: T
authors.lastname: Kamitani
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Matsubara
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sugihara
mesh_terms: D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D007022:Hypotension / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D014630:Vagus Nerve / Q000502:physiology*