76673
document
[ Opposing effects of propranolol and diltiazem on the angina threshold during an exercise test in patients with syndrome X ] . Patients with angina pectoris , exercise induced myocardial ischemia , normal coronary arteries and no evidence of epicardial spasm , i.e . patients with syndrome x , have been suggested to haven inadequate increase in coronary blood flow during tachycardia , possibly due to a functional disorder of small coronary vessels . To evaluate the best medical management of this syndrome we studied 13 patients who showed the above set of findings . Patients were given propranolol ( 160 mg daily ) , diltiazem ( 360 mg daily ) and placebo for 2 weeks , using a randomized single blind protocol . Upright bicycle ergometer testing was performed at the end of each period of treatment . Compared to placebo , diltiazem significantly ( p less than 0.001 ) prolonged exercise duration ( x +/- SD : 365 +/- 86 vs 303 +/- 89 sec ) and time to onset of angina ( 358 +/- 88 vs 276 +/- 90 sec ) . Angina appeared in 7 patients with diltiazem vs 13 patients with placebo and occurred at a higher rate pressure product ( 26.3 +/- 3.5 vs 24.1 +/- 2.8 X 10 ( -3 ) ; p less than 0.02 ) . Conversely , following propranolol exercise duration and time to onset of angina were unchanged and angina appeared in all patients at a lower rate pressure product ( 18.3 +/- 2.9 vs 24.4 +/- 3.6 X 10 ( -3 ) ; p less than 0.001 ) . The most likely explanations for these findings are : propranolol counteracts beta 2-adrenergic receptors , thus further reducing coronary reserve . This may lower the anginal threshold ; Diltiazem reduces smooth muscle tone in small coronary vessels . This may result in increased coronary reserve and exercise duration .
76674
Intervention_Pharmacological
propranolol
76675
Intervention_Pharmacological
diltiazem
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Intervention_Pharmacological
diltiazem
76677
Intervention_Control
placebo
76678
Intervention_Physical
Upright bicycle ergometer testing
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Intervention_Pharmacological
diltiazem
76680
Intervention_Control
placebo
76681
Intervention_Pharmacological
propranolol
76682
Intervention_Pharmacological
Diltiazem
76683
Outcome_Physical
angina threshold
76684
Outcome_Physical
coronary blood flow during tachycardia
76685
Outcome_Physical
exercise duration
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Outcome_Physical
time to onset of angina
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Outcome_Physical
Angina
76688
Outcome_Physical
pressure product
76689
Outcome_Physical
exercise duration and time to onset of angina
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Outcome_Physical
angina
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Outcome_Physical
pressure product
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Outcome_Physical
coronary reserve .
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Outcome_Physical
anginal threshold ;
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Outcome_Physical
smooth muscle tone
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Outcome_Physical
coronary reserve and exercise duration .
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Participant_Condition
patients with syndrome X ]
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Participant_Condition
Patients with angina pectoris , exercise induced myocardial ischemia
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Participant_Condition
normal coronary arteries and no evidence of epicardial spasm
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Participant_Condition
patients with syndrome x
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Participant_Sample-size
13 patients