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Altered sympathetic tone in hypertensives with angina and lowered threshold for pacing ischemia
S Oishi1, A Yurenev, E Parfyonova
1Department of Medicine, University of Southern California, Los Angeles.
Insights
This study suggests that reduced sympathetic nervous system activity may be linked to myocardial ischemia in patients with essential hypertension. Lower plasma norepinephrine levels were observed in patients experiencing ischemia during stress tests.
Area of Science:
- Cardiology
- Neuroscience
- Hypertension Research
Background:
- Essential hypertension is often associated with altered sympathetic nervous system (SNS) activity.
- The role of SNS in myocardial ischemia, particularly silent ischemia, within the context of hypertension requires further elucidation.
- Understanding these interactions is crucial for managing cardiovascular risk in hypertensive patients.
Purpose of the Study:
- To investigate the involvement of the sympathetic nervous system in myocardial ischemia among patients with essential hypertension.
- To compare hemodynamic parameters and plasma norepinephrine levels during rest, pacing-induced ischemia, and exercise treadmill testing (ETT).
Main Methods:
- Twenty patients with essential hypertension and stable angina underwent pacing and ETT after discontinuing antihypertensive therapy.
- Measurements included plasma norepinephrine, heart rate (HR), blood pressure (BP), and the HR·BP double product.
- Patients were categorized based on the presence and characteristics of silent ischemia during stress tests.
Main Results:
- Patients with silent ischemia during ETT exhibited a higher HR·BP product compared to pacing-induced ischemia.
- Lower resting and stress-induced plasma norepinephrine levels were found in patients with ischemia compared to those without.
- Patients with ischemia had significantly lower resting, pacing, and ETT plasma norepinephrine levels than those without ischemia.
Conclusions:
- Reduced sympathetic nervous system tone may be associated with myocardial ischemia in essential hypertension.
- Lower plasma norepinephrine levels in ischemic patients suggest a complex interplay between SNS activity and ischemic events.
- Further research into alpha/beta-receptor responsiveness and vascular constriction is warranted.
Abstract:
To determine the role of the sympathetic nervous system in myocardial ischemia with essential hypertension, plasma norepinephrine, heart rate (HR), blood pressure (BP), and the HR.BP double product at the time of silent ischemia during pacing and exercise treadmill test (ETT) were compared with basal values in 20 patients with sustained essential hypertension and stable angina, 3 to 60 days (12.6 +/- 11.6) after discontinuation of all antihypertensive and coronary vasodilator therapy. Group I (N = 6) had silent ischemia with a higher HR.BP product at ETT than at pacing (ratio = 157 +/- 10.4% [+/- SD] v a value in group II [N = 5] of 102 +/- 18.8 [P less than .01]. Group III (N = 9) had no silent ischemia at ETT or pacing. Group I v group II plasma norepinephrine levels at rest and with pacing silent ischemia were 76 +/- 37 v 138 +/- 36 pg/mL, P less than .02, and 101 +/- 50 v 230 +/- 43 pg/mL, P less than .01, respectively. In groups I and II plasma norepinephrine levels were significantly lower than those of group III. Eleven of 20 patients had ischemia on pacing or ETT. Left ventricular myocardial mass were greater (224 +/- 49 v 180 +/- 28 g, p less than .05), HR (67 +/- 13 v 76 +/- 11 beats/min, P = NS) and plasma norepinephrine levels at rest (104 +/- 47 v 241 +/- 99 pg/mL, P less than .01), pacing (160 +/- 81 v 338 +/- 94 pg/mL, P less than .01), and ETT (758 +/- 268 v 1203 +/- 611 pg/mL, P less than .05), were lower in patients with ischemia (N = 11, group II) than in patients without ischemia (N = 9, group III) on pacing or ETT. Eight patients were on reserpine prestudy; reserpine prestudy was associated with lower basal HR (63 +/- 9 v 76 +/- 12 beats/min, P less than .05) and plasma norepinephrine (106 +/- 48 v 169 +/- pg/mL, P less than .07) and greater ratio of HR.BP double product on ETT/pacing, (141 +/- 33 v 111 +/- 19, P less than .02). The sympathetic nervous tone of group I was low at baseline but there may have been raised alpha/beta-receptor responsiveness to laboratory stresses with concomitant micro/macrovascular constriction at higher oxygen demand.(ABSTRACT TRUNCATED AT 400 WORDS)