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Evaluation of reperfusion hyperemia with myocardial contrast echocardiography
1Wishard Memorial Hospital, Krannert Institute of Cardiology, Indianapolis, IN 46202.
Insights
Myocardial contrast echocardiography effectively measures reperfusion hyperemia by correlating image intensity changes with coronary blood flow. This technique quantifies reactive hyperemia following temporary coronary artery occlusion and release in canine models.
Area of Science:
- Cardiovascular Research
- Diagnostic Imaging
- Echocardiography
Background:
- Assessing myocardial reperfusion after coronary artery occlusion is critical for understanding cardiac recovery.
- Traditional methods for evaluating blood flow can be invasive or lack real-time quantitative data.
- Myocardial contrast echocardiography (MCE) offers a non-invasive approach to visualize and quantify myocardial perfusion.
Purpose of the Study:
- To evaluate the utility of myocardial contrast echocardiography in assessing reperfusion hyperemia.
- To correlate objective measurements of MCE image intensity with coronary blood flow dynamics.
- To investigate MCE's ability to detect reactive hyperemia following temporary coronary artery occlusion.
Main Methods:
- An open-chest canine model was utilized with temporary occlusion of the left circumflex coronary artery.
- Myocardial contrast echocardiography was performed using agitated sodium diatrizoate and saline solution injected into the aortic root.
- Coronary blood flow and myocardial image intensity changes were measured at baseline, during occlusion, and at various time points after reperfusion.
Main Results:
- Coronary blood flow significantly decreased during occlusion and markedly increased (p < 0.001) during reperfusion, demonstrating reactive hyperemia.
- Myocardial image intensity change after contrast injection showed a significant decline during occlusion (p < 0.001) and a substantial increase during reperfusion (p < 0.001).
- A strong positive correlation (r = 0.67, p < 0.001) was observed between myocardial image intensity change and coronary blood flow across all study conditions.
Conclusions:
- Myocardial contrast echocardiography provides objective measurements that correlate well with coronary blood flow.
- Changes in myocardial image intensity accurately reflect increases in coronary flow associated with reactive hyperemia.
- MCE is a valuable tool for evaluating reperfusion and hyperemia in the context of coronary artery occlusion.
Abstract:
In this study we used myocardial contrast echocardiography to evaluate reperfusion hyperemia in an open-chest canine model of temporary coronary artery occlusion. Eight dogs had coronary occluders and electromagnetic flow probes on the left circumflex coronary artery. Aortic root injections of agitated sodium diatrizoate and saline solution were used for myocardial contrast. Data were collected at baseline (n = 16), during coronary occlusion (n = 18), immediately after coronary release (n = 18), and 5 minutes after coronary artery release (n = 12). Baseline coronary flow was 23.8 +/- 5.9 ml/min, decreasing to 0 ml/min during coronary occlusion. Immediately after coronary release flow was 96.6 +/- 41 ml/min (p less than 0.001 compared with baseline), and 5 minutes after coronary release flow was 68.2 +/- 27.9 ml/min (p less than 0.001 compared with baseline). The myocardial image intensity change after injection of contrast material was 74.25 +/- 30.6 ml/min at baseline and declined to 10.4 +/- 10.9 ml/min during coronary occlusion (p less than 0.001 compared with baseline). During reperfusion hyperemia image intensity change was 102.3 +/- 33.3 ml/min (p less than 0.001 compared with occlusion, p less than 0.02 compared with baseline, p less than 0.001 compared with remote regions). Considering all observations, myocardial image intensity change after contrast injection correlated positively with coronary flow (r = 0.67, p less than 0.001). Correlations within individual dogs ranged from r = 0.70 to 0.98. We conclude that image intensity change after aortic root injection of echocardiographic contrast correlates with coronary blood flow. Objective measurements of contrast intensity reflect increases in coronary flow associated with reactive hyperemia after coronary occlusion and release.