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Increased blood pressure and neural tone in the silent ischemia of hypertension: disparate effects of immediate release nifedipine.

AbstractOBJECTIVES:
The aims of this study were 1) to evaluate the role of blood pressure and associated neural tonicity in ambient ischemia of a group of hypertensive patients with stable angina, and 2) to determine the efficacy of immediate release nifedipine therapy in controlling the total ischemic burden in both office-measured and ambulatory blood pressure.
BACKGROUND:
Low heart rate ischemia, as detected by Holter ambulatory electrocardiographic monitoring, suggests that reduced coronary flow is the major factor leading to ischemia. We previously found that 91% of the ischemic episodes in our hypertensive patients with stable angina were silent.
METHODS:
We measured plasma norepinephrine content during ischemic events from blood obtained from automatic pump withdrawal with the assistance of a real-time ST segment depression monitor. We then related the norepinephrine content to ischemic episodes assessed by 48-h Holter recording, blood pressure reading by ambulatory blood pressure monitoring and patients' diaries. Measurements were taken during the placebo period and immediate-release nifedipine therapy in 30 hypertensive patients (20 with and 10 without stable angina).
RESULTS:
More than half of the patients had ischemic episodes; 95% of these were silent. Ischemic episodes peaked in the early morning, and 55% occurred during routine sedentary activities. There was a 10% to 15% increase in heart rate at the onset of ischemia associated with a 30% higher plasma norepinephrine level. Seventy-five percent of patients had increased norepinephrine after nifedipine therapy. Nifedipine therapy controlled measured blood pressure but not 24-h ambulatory blood pressure. Ischemic episodes were reduced only in patients whose ambulatory blood pressure was controlled.
CONCLUSIONS:
The results suggest that increased neural tone at the time of the ischemic event may play a role in reducing coronary perfusion leading to silent ischemia. Nifedipine therapy (immediate release) was effective in control of ischemia only when both ambulatory and office-measured blood pressure were controlled.
AuthorsD D Lee, K Rigonan, V Dequattro
JournalJournal of the American College of Cardiology (J Am Coll Cardiol) Vol. 22 Issue 5 Pg. 1438-45 (Nov 1 1993) ISSN: 0735-1097 [Print] UNITED STATES
PMID8227803 (Publication Type: Clinical Trial, Journal Article, Randomized Controlled Trial, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
Chemical References
  • Nifedipine
  • Norepinephrine
  • Epinephrine
Topics
  • Activities of Daily Living
  • Adult
  • Aged
  • Angina Pectoris (complications, diagnosis, drug therapy, physiopathology)
  • Blood Pressure (drug effects)
  • Circadian Rhythm
  • Echocardiography
  • Electrocardiography, Ambulatory
  • Epinephrine (blood)
  • Female
  • Heart Rate
  • Humans
  • Hypertension (complications, diagnosis, drug therapy, physiopathology)
  • Male
  • Middle Aged
  • Myocardial Ischemia (complications, diagnosis, drug therapy, physiopathology)
  • Nifedipine (pharmacology, therapeutic use)
  • Norepinephrine (blood)
  • Sympathetic Nervous System (physiopathology)

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