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Regional myocardial blood flow and left ventricular diastolic properties in pacing-induced ischemia
S Momomura1, J J Ferguson, M J Miller
1Charles A. Dana Research Institute, Beth Israel Hospital, Boston, Massachusetts 02215.
Insights
Critical coronary stenoses impair left ventricular diastolic function during tachycardia. Myocardial blood flow decreases in ischemic regions, affecting heart distensibility and blood supply during increased heart rate.
Area of Science:
- Cardiovascular Physiology
- Ischemic Heart Disease Research
- Cardiac Diastolic Function
Background:
- Left ventricular diastolic abnormalities can compromise cardiac function.
- Understanding myocardial blood flow dynamics during ischemia is crucial for managing heart conditions.
Purpose of the Study:
- To investigate the relationship between left ventricular diastolic abnormalities and myocardial blood flow during induced ischemia.
- To assess the impact of critical coronary stenoses on diastolic distensibility and regional blood flow during tachycardia.
Main Methods:
- Eight open-chest dogs with induced critical coronary stenoses underwent pacing tachycardia.
- Left ventricular pressures, segment lengths, and myocardial blood flow were measured using pressure catheters, sonomicrometry, and microspheres.
- Coronary blood flow and vascular resistance were assessed using flow meters.
Main Results:
- Pacing tachycardia increased left ventricular end-diastolic pressure and segment lengths in ischemic regions, indicating decreased diastolic distensibility.
- In dogs with stenoses, regional coronary vascular resistance did not decrease during tachycardia.
- Subendocardial myocardial blood flow and the subendocardial to subepicardial ratio decreased significantly in the left anterior descending coronary artery territory during pacing tachycardia.
Conclusions:
- Critical coronary stenoses lead to impaired left ventricular diastolic distensibility during tachycardia.
- Myocardial blood flow is compromised in ischemic regions under conditions of increased heart rate, exacerbating ischemia.
Abstract:
The relation between left ventricular diastolic abnormalities and myocardial blood flow during ischemia was studied in eight open chest dogs with critical stenoses of the proximal left anterior descending and circumflex coronary arteries. The heart was paced at 1.7 times the heart rate at rest for 3 min. In dogs with coronary stenoses, left ventricular end-diastolic pressure increased from 8 +/- 1 to 14 +/- 2 mm Hg during pacing tachycardia (p less than 0.01) and 16 +/- 3 mm Hg (p less than 0.01) after pacing, with increased end-diastolic and end-systolic segment lengths in the ischemic regions. Left ventricular diastolic pressure-segment length relations for ischemic regions shifted upward during and after pacing tachycardia in dogs with coronary stenoses, indicating decreased regional diastolic distensibility. In dogs without coronary stenoses, the left ventricular diastolic pressure-segment length relation was unaltered. Pacing tachycardia without coronary stenoses induced an increase in anterograde coronary blood flow (assessed by flow meter) in both the left anterior descending and circumflex coronary arteries, and a decrease in regional vascular resistance. In dogs with coronary stenoses, regional vascular resistance before pacing was decreased by 18%; myocardial blood flow (assessed by microspheres) was unchanged in both the left anterior descending and circumflex coronary artery territories. During pacing tachycardia with coronary stenoses, regional coronary vascular resistance did not decrease further; subendocardial myocardial blood flow distal to the left anterior descending coronary artery stenosis decreased (from 1.03 +/- 0.07 to 0.67 +/- 0.12 ml/min per g, p less than 0.01), as did subendocardial to subepicardial blood flow ratio (from 1.04 +/- 0.09 to 0.42 +/- 0.08, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)