What is the clinical evidence from this study?

Study design: Other. Population: Formalin-induced heart block (n=16). Intervention: Ventricular paired pacing vs. Normal ventricular pacing. Primary outcome: Reactive hyperemic repayment.

What question did this study set out to answer?

To determine whether coronary reactive hyperemia following a single brief diastolic occlusion is coupled to myocardial metabolic activity and oxygen consumption.

July 1, 1987AJP Heart and Circulatory Physiology

Metabolic mediation of single brief diastolic occlusion reactive hyperemic responses

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Key result

Ventricular paired pacing resulted in a reactive hyperemic repayment of 189% compared to 94% when flow and pressure were matched via drug infusion, indicating metabolic mediation.

Population

16 conscious dogs with Formalin-induced heart block

Comparison

400-ms diastolic occlusion during higher… vs 400-ms diastolic occlusion during normal…

Design

Preclinical

Authors

NSNorman SadickThe University of Sydney GDGregory P. DubéGeneral Sciences (United States)PMP. A. McHaleUniversity of Minnesota

Discussion

Member takes

Implication

Metabolic mediation predominates in coronary reactive hyperemia; supports mechanistic insight in animals but leaves open human translation.

Key Points

To determine whether coronary reactive hyperemia following a single brief diastolic occlusion is coupled to myocardial metabolic activity and oxygen consumption.
Assessed 16 conscious dogs with Formalin-induced heart block subjected to 400-ms diastolic coronary occlusions during normal ventricular pacing and ventricular paired pacing.
Administered intravenous infusions of adenosine and phenylephrine during normal pacing to match the mean aortic pressure and coronary flow of paired pacing while maintaining baseline oxygen consumption.
A 400-ms diastolic occlusion elicited a reactive hyperemic repayment of 216 ± 22% during normal pacing and 189 ± 18% during paired pacing despite significant elevations in myocardial oxygen consumption and mean coronary blood flow.
Pharmacological matching of aortic pressure and coronary flow without elevated metabolic demand significantly reduced reactive hyperemic repayment to 94 ± 22% compared with paired pacing.

Structured PICO

Population

16 conscious dogs with Formalin-induced heart block.

Intervention

400-ms diastolic occlusion during higher myocardial metabolic activity (ventricular paired pacing) or during normal pacing with adenosine and phenylephrine infusion

Comparator

400-ms diastolic occlusion during normal ventricular pacing

Outcome

Reactive hyperemic repaymentsurrogate

Main Result

Absolute Event Rate: 189% vs 216%

The magnitude of coronary reactive hyperemia following a brief diastolic occlusion is primarily driven by myocardial metabolic activity.

Cite This Study

Sadick et al. (1987) studied Formalin-induced heart block (n=16). Ventricular paired pacing vs. Normal ventricular pacing was evaluated on Reactive hyperemic repayment. Ventricular paired pacing resulted in a reactive hyperemic repayment of 189% compared to 94% when flow and pressure were matched via drug infusion, indicating metabolic mediation.

synapsesocial.com/papers/6a9ea721ee65424cc3231cb9 https://doi.org/10.1152/ajpheart.1987.253.1.h25

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Implication

Metabolic mediation predominates in coronary reactive hyperemia; supports mechanistic insight in animals but leaves open human translation.