Contrasting effects of nitroprusside and phentolamine in experimental myocardial infarction

K Ramanathan, Monty M. Bodenheimer, Vidya S. Banka, Surrender Raina, Richard H. Helfant

Research output: Contribution to journalArticle

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Abstract

Phentolamine and nitroprusside have recently been shown to improve myocardial performance in the presence of ischemia. The comparative effects of these agents on both local contraction and degree of ischemia in central ischemic, border and nonischemic zones were studied in 10 dogs using Walton-Brodie strain gauges and epicardial electrograms (8 to 12 sites). After coronary occlusion, total tension and rate of tension rise in the border zone decreased to 80.0 ± 8.5 and 76.0 ± 10.5 percent, respectively, whereas total S-T elevation increased from 7.1 ± 2.1 to 117.6 ± 12.1 mv. Tension in the nonischemic zone decreased slightly but not significantly (88.5 ± 9.1 percent). Phentolamine (0.25-2.0 mg/min) decreased systolic pressure by 21.4 ± 2.2 mm Hg and increased tension in the border zone from 80.0 ± 8.5 to 100.4 ± 10.8 percent (P <0.005) and rate of tension rise from 76.0 ± 10.5 to 99.5 ± 12.0 percent (P <0.005). Nitroprusside (40 to 200 μg/min) similarly decreased systolic blood pressure by 18.2 ± 1.2 mm Hg and increased tension in the border zone from 77.0 ± 10.6 to 83.5 ± 8.5 percent (P <0.05) and rate of tension rise from 67.8 ± 7.7 to 81.3 ± 7.3 percent (P <0.05). Tension in the nonischemic zone was increased by both phentolamine (P <0.025) and nitroprusside (P <0.05) whereas that in the central ischemic zone was unchanged. However, phentolamine increased the heart rate from 158.3 ± 4.5 to 181.1 ± 5.3 beats/min (P <0:001) and increased the total S-T elevation from 117.6 ± 12.1 to 128.7 ± 11.8 my (P <0.02). Nitroprusside did not change the heart rate, and total S-T elevation decreased from 123.6 ± 8.8 to 115.0 ± 8.9 my (P <0.05). Atrial pacing combined with nitroprusside to increase heart rate to a rate similar to that with phentolamine Increased total S-T elevation from 115.0 ± 8.9 to 125.1 ± 8.9 my (P <0.02) without significantly affecting tension. Thus, both phentolamine and nitroprusside improve local myocardial contractile ability. However, phentolamine, in contrast to nitroprusside, increases the area of ischemic injury as measured by S-T segment elevation. In part, this effect of phentolamine is due to its positive chronotropic action. Thus, each vasodilator agent must be evaluated individually to assess its action in the setting of acute myocardial infarction.

Original languageEnglish (US)
Pages (from-to)994-999
Number of pages6
JournalAmerican Journal of Cardiology
Volume39
Issue number7
DOIs
StatePublished - Jan 1 1977
Externally publishedYes

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Phentolamine
Nitroprusside
Myocardial Infarction
Heart Rate
Blood Pressure
Ischemia
Coronary Occlusion
Vasodilator Agents
Dogs

All Science Journal Classification (ASJC) codes

  • Cardiology and Cardiovascular Medicine

Cite this

Contrasting effects of nitroprusside and phentolamine in experimental myocardial infarction. / Ramanathan, K; Bodenheimer, Monty M.; Banka, Vidya S.; Raina, Surrender; Helfant, Richard H.

In: American Journal of Cardiology, Vol. 39, No. 7, 01.01.1977, p. 994-999.

Research output: Contribution to journalArticle

Ramanathan, K ; Bodenheimer, Monty M. ; Banka, Vidya S. ; Raina, Surrender ; Helfant, Richard H. / Contrasting effects of nitroprusside and phentolamine in experimental myocardial infarction. In: American Journal of Cardiology. 1977 ; Vol. 39, No. 7. pp. 994-999.
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N2 - Phentolamine and nitroprusside have recently been shown to improve myocardial performance in the presence of ischemia. The comparative effects of these agents on both local contraction and degree of ischemia in central ischemic, border and nonischemic zones were studied in 10 dogs using Walton-Brodie strain gauges and epicardial electrograms (8 to 12 sites). After coronary occlusion, total tension and rate of tension rise in the border zone decreased to 80.0 ± 8.5 and 76.0 ± 10.5 percent, respectively, whereas total S-T elevation increased from 7.1 ± 2.1 to 117.6 ± 12.1 mv. Tension in the nonischemic zone decreased slightly but not significantly (88.5 ± 9.1 percent). Phentolamine (0.25-2.0 mg/min) decreased systolic pressure by 21.4 ± 2.2 mm Hg and increased tension in the border zone from 80.0 ± 8.5 to 100.4 ± 10.8 percent (P <0.005) and rate of tension rise from 76.0 ± 10.5 to 99.5 ± 12.0 percent (P <0.005). Nitroprusside (40 to 200 μg/min) similarly decreased systolic blood pressure by 18.2 ± 1.2 mm Hg and increased tension in the border zone from 77.0 ± 10.6 to 83.5 ± 8.5 percent (P <0.05) and rate of tension rise from 67.8 ± 7.7 to 81.3 ± 7.3 percent (P <0.05). Tension in the nonischemic zone was increased by both phentolamine (P <0.025) and nitroprusside (P <0.05) whereas that in the central ischemic zone was unchanged. However, phentolamine increased the heart rate from 158.3 ± 4.5 to 181.1 ± 5.3 beats/min (P <0:001) and increased the total S-T elevation from 117.6 ± 12.1 to 128.7 ± 11.8 my (P <0.02). Nitroprusside did not change the heart rate, and total S-T elevation decreased from 123.6 ± 8.8 to 115.0 ± 8.9 my (P <0.05). Atrial pacing combined with nitroprusside to increase heart rate to a rate similar to that with phentolamine Increased total S-T elevation from 115.0 ± 8.9 to 125.1 ± 8.9 my (P <0.02) without significantly affecting tension. Thus, both phentolamine and nitroprusside improve local myocardial contractile ability. However, phentolamine, in contrast to nitroprusside, increases the area of ischemic injury as measured by S-T segment elevation. In part, this effect of phentolamine is due to its positive chronotropic action. Thus, each vasodilator agent must be evaluated individually to assess its action in the setting of acute myocardial infarction.

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