What question did this study set out to answer?

To determine whether prolonged pacing-induced tachycardia directly causes myocardial infarction in the setting of fixed coronary stenosis that produces no ischemia at rest.

May 1, 1999Anesthesia & Analgesia

Tachycardia-Induced Subendocardial Necrosis in Acutely Instrumented Dogs with Fixed Coronary Stenosis

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Why the study?

Does prolonged tachycardia-induced ischemia cause myocardial infarction in dogs with fixed coronary stenosis?

Key Points

To determine whether prolonged pacing-induced tachycardia directly causes myocardial infarction in the setting of fixed coronary stenosis that produces no ischemia at rest.
In 17 anesthetized dogs with fixed proximal left anterior descending coronary stenosis, animals were randomly assigned to control resting heart rate (~90 bpm for 4 h, n=6), 4-hour pacing tachycardia (150 bpm, n=6), or 1-hour pacing tachycardia (150 bpm, n=5).
Myocardial blood flow was measured using radiolabeled microspheres, and the area of necrosis was quantified using triphenyl-tetrazolium chloride staining.
Infarct area was significantly greater in the 4-hour ischemia group (15.5% ± 9.1%) compared to the 1-hour ischemia group (1.6% ± 2.1%) and the control group (0.09% ± 0.2%) (P < 0.002).
Patchy subendocardial necrosis developed in 100% (6/6) of the 4-hour ischemia dogs, 40% (2/5) of the 1-hour ischemia dogs, and 16.7% (1/6) of control dogs.
Relative subendocardial blood flow at the end of ischemia was significantly reduced in both the 4-hour (0.3 ± 0.1, P = 0.008) and 1-hour (0.4 ± 0.1, P = 0.01) groups compared with controls (0.9 ± 0.2).

Structured PICO

Does prolonged tachycardia-induced ischemia cause myocardial infarction in dogs with fixed coronary stenosis?

Population

17 anesthetized dogs with proximal left anterior descending (LAD) artery cannulated and perfused via bypass, with distal LAD pressure reduced by a screw clamp to cause ≥20% decrease in wall thickening during pacing tachycardia but no decrease in resting heart rate (approximately 90 bpm).

Intervention

Pacing tachycardia at 150 bpm for 4 hours (n=6) or 1 hour (n=5).

Comparator

Control group (n=6) maintained at resting heart rate (approximately 90 bpm) and mean coronary pressure of 49+/-5 mm Hg for 4 hours.

Outcome

Infarct area measured by triphenyl-tetrazolium chloride staining and myocardial blood flow measured by radiolabeled microspheres.surrogate

Prolonged tachycardia-induced ischemia in the presence of fixed coronary stenosis leads to subendocardial infarction in dogs, suggesting a possible mechanism for postoperative myocardial infarction.

Discussion

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Implication

Prolonged tachycardia-induced ischemia may produce subendocardial infarction in stenotic models; leaves open translation to human perioperative MI.

Cite This Study

Landesburg et al. (1999) studied this question.

synapsesocial.com/papers/6a0f50695093bfd8189bcfcb https://doi.org/10.1097/00000539-199905000-00002

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Implication

Prolonged tachycardia-induced ischemia may produce subendocardial infarction in stenotic models; leaves open translation to human perioperative MI.

Tachycardia-Induced Subendocardial Necrosis in Acutely Instrumented Dogs with Fixed Coronary Stenosis

Key Points

Structured PICO

Discussion

Implication

Cite This Study

Tachycardia-Induced Subendocardial Necrosis in Acutely Instrumented Dogs with Fixed Coronary Stenosis

Key Points

Structured PICO

Discussion

Implication

Cite This Study

Also Consider

Also Consider