Comparison of hemodynamics, cardiac electrophysiology, and ventricular arrhythmia in an open- and a closed-chest porcine model of acute myocardial infarction

et al. 2020

Preprint

Background: Targeted hypothermia, as used after cardiac arrest, increases electrical and mechanical systolic duration. Differences in duration of mechanical and electrical systole are correlated to ventricular arrhythmias. The electromechanical window (EMW) becomes negative when electrical systole outlasts the mechanical systole. Prolonged electrical systole is also associated with electrical and mechanical dispersion, both predisposing for arrhythmias. The electromechanical relations during targeted hypothermia are unknown, but treatment after cardiac arrest has not demonstrated increased incidence of ventricular arrhythmic events.We wanted to explore the electromechanical relations during hypothermia at 33 °C. We hypothesized that targeted hypothermia would increase electrical and mechanical systolic duration without an increase in electromechanical negativity, nor an increase in electrical and mechanical dispersion. Methods: In a porcine model (n = 14) we registered electrocardiogram (ECG) and echocardiographic recordings during 38 °C and 33 °C, at spontaneous and atrial paced heart rate 100 beats/min. EMW was calculated by subtracting electrical systole, QT interval, from the corresponding mechanical systole, recorded from onset QRS to aortic valve closure. Electrical dispersion was measured as time from peak to end of the ECG T wave. Mechanical dispersion was calculated by strain echocardiography as standard deviation of time to peak strain. Results:Electrical systole increased during hypothermia at spontaneous heart rate (p < 0.001) and heart rate 100 beats/min (p = 0.005). Mechanical systolic duration was prolonged and outlasted electrical systole independently of heart rate (p < 0.001). EMW changed from negative to positive value (-20 ± 19 to 27 ± 34 ms, p = 0.001). The positivity was even more pronounced at heart rate 100 beats/min (-25 ± 26 to 41 ± 18 ms, p < 0.001). Electrical dispersion decreased (p = 0.027 and p = 0.003), while mechanical dispersion did not differ (p = 0.078 and p = 0.297).Conclusion: Targeted hypothermia increased electrical and mechanical systolic duration, the electromechanical window became positive, electrical dispersion was reduced and mechanical dispersion was unchanged. These alterations may have clinical importance. Further clinical studies are required to clarify whether corresponding electromechanical alterations are accommodating in humans.

Section: The Shift In Electromechanical Windowsupporting

confidence: 65%

“…The open chest model may have altered the preload and afterload conditions [32]. However, we analysed the absolute change in the parameters during the intervention in a controlled manner with no surgical or physiological modi cation.…”

Section: Limitationsmentioning

confidence: 99%

Changes in Left Ventricular Electromechanical Relations During Targeted Hypothermia

et al. 2020

Preprint

“…In our in vivo model, baseline EMW was slightly negative at both heart rates. The normal value for EMW in land race pigs during normothermia is unknown, but an open chest model can lead to a prolonged QT interval which may contribute to EMW negativity [21]. In an ex vivo model, isolated Langendorff-perfused Göttingen minipig hearts baseline EMW was 134 ms [22].…”

Section: The Shift In Electromechanical Windowmentioning

confidence: 99%

“…The methods used to identify electrical intervals were identical for all measurements and the reproducibility of the measurements was good. The open chest model may have altered the preload and afterload conditions [21]. However, we analysed the absolute change in the parameters during stable phases.…”

Section: Limitationsmentioning

confidence: 99%

Changes in left ventricular electromechanical relations during targeted hypothermia

et al. 2020

ICMx

Background Targeted hypothermia, as used after cardiac arrest, increases electrical and mechanical systolic duration. Differences in duration of electrical and mechanical systole are correlated to ventricular arrhythmias. The electromechanical window (EMW) becomes negative when the electrical systole outlasts the mechanical systole. Prolonged electrical systole corresponds to prolonged QT interval, and is associated with increased dispersion of repolarization and mechanical dispersion. These three factors predispose for arrhythmias. The electromechanical relations during targeted hypothermia are unknown. We wanted to explore the electromechanical relations during hypothermia at 33 °C. We hypothesized that targeted hypothermia would increase electrical and mechanical systolic duration without more profound EMW negativity, nor an increase in dispersion of repolarization and mechanical dispersion. Methods In a porcine model (n = 14), we registered electrocardiogram (ECG) and echocardiographic recordings during 38 °C and 33 °C, at spontaneous and atrial paced heart rate 100 beats/min. EMW was calculated by subtracting electrical systole; QT interval, from the corresponding mechanical systole; QRS onset to aortic valve closure. Dispersion of repolarization was measured as time from peak to end of the ECG T wave. Mechanical dispersion was calculated by strain echocardiography as standard deviation of time to peak strain. Results Electrical systole increased during hypothermia at spontaneous heart rate (p < 0.001) and heart rate 100 beats/min (p = 0.005). Mechanical systolic duration was prolonged and outlasted electrical systole independently of heart rate (p < 0.001). EMW changed from negative to positive value (− 20 ± 19 to 27 ± 34 ms, p = 0.001). The positivity was even more pronounced at heart rate 100 beats/min (− 25 ± 26 to 41 ± 18 ms, p < 0.001). Dispersion of repolarization decreased (p = 0.027 and p = 0.003), while mechanical dispersion did not differ (p = 0.078 and p = 0.297). Conclusion Targeted hypothermia increased electrical and mechanical systolic duration, the electromechanical window became positive, dispersion of repolarization was slightly reduced and mechanical dispersion was unchanged. These alterations may have clinical importance. Further clinical studies are required to clarify whether corresponding electromechanical alterations are accommodating in humans.

“…The open chest model may have altered the preload and afterload conditions [21]. However, we analysed the absolute change in the parameters during stable phases.The pigs were anaesthetized with iso urane and morphine after induction with pentobarbital.…”

Section: Goodmentioning

confidence: 99%

Changes in left ventricular electromechanical relations during targeted hypothermia

et al. 2020

Preprint

Background:Targeted hypothermia, as used after cardiac arrest, increases electrical and mechanical systolic duration. Differences in duration of electrical and mechanical systole are correlated to ventricular arrhythmias. The electromechanical window (EMW) becomes negative when the electrical systole outlasts the mechanical systole. Prolonged electrical systole corresponds to prolonged QT interval, and is associated with increased dispersion of repolarization and mechanical dispersion. These three factors predispose for arrhythmias. The electromechanical relations during targeted hypothermia are unknown.We wanted to explore the electromechanical relations during hypothermia at 33 °C. We hypothesized that targeted hypothermia would increase electrical and mechanical systolic duration without an increase in EMW negativity, nor an increase in dispersion of repolarization and mechanical dispersion.Methods: In a porcine model (n = 14) we registered electrocardiogram (ECG) and echocardiographic recordings during 38 °C and 33 °C, at spontaneous and atrial paced heart rate 100 beats/min. EMW was calculated by subtracting electrical systole; QT interval, from the corresponding mechanical systole; QRS onset to aortic valve closure. Dispersion of repolarization was measured as time from peak to end of the ECG T wave. Mechanical dispersion was calculated by strain echocardiography as standard deviation of time to peak strain. Results:Electrical systole increased during hypothermia at spontaneous heart rate (p < 0.001) and heart rate 100 beats/min (p = 0.005). Mechanical systolic duration was prolonged and outlasted electrical systole independently of heart rate (p < 0.001). EMW changed from negative to positive value (-20 ± 19 to 27 ± 34 ms, p = 0.001). The positivity was even more pronounced at heart rate 100 beats/min (-25 ± 26 to 41 ± 18 ms, p < 0.001). Dispersion of repolarization decreased (p = 0.027 and p = 0.003), while mechanical dispersion did not differ (p = 0.078 and p = 0.297).Conclusion:Targeted hypothermia increased electrical and mechanical systolic duration, the electromechanical window became positive, dispersion of repolarization was slightly reduced and mechanical dispersion was unchanged. These alterations may have clinical importance. Further clinical studies are required to clarify whether corresponding electromechanical alterations are accommodating in humans.