Assessment of Myocardial Function During Blood Pressure Manipulations Using Feature Tracking Cardiovascular Magnetic...

Area of Science:

• Cardiovascular Physiology
• Medical Imaging
• Anesthesiology

Background:

• Coronary autoregulation maintains myocardial blood flow across a range of mean arterial pressures (MAP).
• Hypotensive and hypertensive episodes can occur in emergency or peri-operative situations.
• The impact of rapid blood pressure changes outside the autoregulation zone (ARZ) on ventricular function is not well-established.

Purpose of the Study:

• To investigate the effects of blood pressure variations outside the ARZ on left (LV) and right ventricular (RV) function.
• To assess myocardial oxygenation and ventricular mechanics using cardiovascular magnetic resonance (CMR) imaging.

Main Methods:

• Anesthetized swine (n=10) underwent MAP manipulation from 29 to 196 mmHg within a 3-Tesla MRI scanner.
• CMR imaging, including oxygenation-sensitive (OS) cine sequences, was performed at each MAP level.
• Arterial and coronary sinus blood gases, and coronary blood flow were measured; LV and RV strain parameters were quantified using CMR feature tracking.

Main Results:

• Both LV and RV peak strain were compromised below the lower and above the upper limits of the ARZ compared to baseline.
• LV strain showed a non-linear relationship with oxygenation measures.
• Below the ARZ, LV systolic dysfunction correlated with myocardial deoxygenation and reduced coronary blood flow; both systolic and diastolic dysfunction were linked to reduced coronary blood flow.

Conclusions:

• Biventricular function is compromised outside the coronary ARZ in an animal model.
• Hypotension-induced dysfunction is linked to insufficient blood flow and deoxygenation.
• Hypertension-induced dysfunction is attributed to high afterload.
• Findings suggest myocardial deformation can guide blood pressure management in clinical settings, especially considering individual autoregulation thresholds.