Moderate Hypothermia Attenuates Pro-Arrhythmic Electromechanical Relations in the Left Ventricle – A Clinical Study

Abstract BackgroundTargeted temperature management is recommended after cardiac arrest, but the beneficial effects are controversial. The recently published TTM2 study reports that arrhythmias causing hemodynamic compromise are more common during moderate hypothermia. The causation is not explored. Experimentally, moderate hypothermia attenuates electromechanical relations with pro-arrhythmic impact. Mechanical systole outlasts the electrical systole to a greater extent giving increased electromechanical window positivity, and dispersion of electrical and mechanical activity are unaltered. In this prospective clinical study, we explored the effect of moderate hypothermia on electromechanical relations in un-insulted left ventricles. We hypothesized that during moderate hypothermia, prolongation of systolic duration would exceed electrical duration without dispersed electrical- or mechanical activity. Methods20 patients with normal left ventricular function, undergoing surgery on the ascending aorta and connected to cardiopulmonary bypass, were included. Measurements were obtained at 36 °C and 32 °C prior to aortic-repair, and at 36 °C after repair at spontaneous and paced heart rate 90 bpm. Comparable loading conditions were ensured and cardiopulmonary bypass was reduced to 20% of estimated maximum during the measurements. Global cardiac function was measured invasively and with echocardiography. Electromechanical window, dispersion of repolarization by ECG and mechanical dispersion by echocardiography, were calculated. ResultsAt moderate hypothermia (32°C), mechanical systolic prolongation exceeded electrical prolongation so that electromechanical window increased (29 ± 30 to 86 ± 50 ms, p <0.001). Dispersion of repolarization and mechanical dispersion remained unchanged. Myocardial function was preserved with maintained strain, fractional shortening and stroke volume. Similar electromechanical relations were present also at comparable increased heart rate during moderate hypothermia. After rewarming to 36°C, electromechanical alterations were reversed. ConclusionModerate hypothermia increased electromechanical window positivity. Dispersion of repolarisation, mechanical dispersion, and myocardial function were unchanged. Moderate hypothermia did not induce adverse electromechanical changes in the left ventricle during standardized conditions, but rather an attenuation of pro-arrhythmic electromechanical relations.

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Changes in left ventricular electromechanical relations during targeted hypothermia

Intensive Care Medicine Experimental ◽

10.1186/s40635-020-00363-7 ◽

2020 ◽

Vol 8 (1) ◽

Author(s):

Kristin Wisløff-Aase ◽

Viesturs Kerans ◽

Kristina Haugaa ◽

Per Steinar Halvorsen ◽

Helge Skulstad ◽

...

Keyword(s):

Heart Rate ◽

Qt Interval ◽

Clinical Importance ◽

Left Ventricular ◽

Peak Strain ◽

Time To Peak ◽

Mechanical Dispersion ◽

Dispersion Of Repolarization ◽

Aortic Valve Closure ◽

Prolonged Qt Interval

Abstract 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.

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Changes in left ventricular electromechanical relations during targeted hypothermia

10.21203/rs.3.rs-52353/v2 ◽

2020 ◽

Author(s):

Kristin Wisløff-Aase ◽

Viesturs Kerans ◽

Kristina Haugaa ◽

Per Steinar Halvorsen ◽

Helge Skulstad ◽

...

Keyword(s):

Heart Rate ◽

Qt Interval ◽

Clinical Importance ◽

Left Ventricular ◽

Peak Strain ◽

Time To Peak ◽

Mechanical Dispersion ◽

Dispersion Of Repolarization ◽

Aortic Valve Closure ◽

Prolonged Qt Interval

Abstract 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.

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Effect of heart rate on left ventricular longitudinal myocardial function in type 2 diabetes mellitus

Cardiovascular Diabetology ◽

10.1186/s12933-021-01278-7 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Yuki Yamauchi ◽

Hidekazu Tanaka ◽

Shun Yokota ◽

Yasuhide Mochizuki ◽

Yuko Yoshigai ◽

...

Keyword(s):

Diabetes Mellitus ◽

Type 2 Diabetes ◽

Heart Rate ◽

Type 2 Diabetes Mellitus ◽

Myocardial Function ◽

Normal Subjects ◽

Left Ventricular ◽

High Heart Rate ◽

Lv Dysfunction

Abstract Background Left ventricular (LV) longitudinal myocardial dysfunction is considered a marker of preclinical LV dysfunction in patients with type 2 diabetes mellitus (T2DM). High heart rate (HR) is associated with cardiovascular outcomes, but the effect of HR on LV longitudinal myocardial function in T2DM patients is uncertain. Methods We studied 192 T2DM patients with preserved LV ejection fraction (LVEF), and 81 age-, sex-, and LVEF-matched healthy volunteers. HR was measured as the average HR during echocardiography, and high HR was defined as resting HR ≥ 70 beats/minute. LV longitudinal myocardial function was assessed as global longitudinal strain (GLS). The predefined cutoff for subclinical LV dysfunction was set at GLS < 18%. Results GLS in T2DM patients with high HR was significantly lower than that in T2DM patients with low HR (16.3% ± 4.2% vs. 17.8% ± 2.8%; P = 0.03), whereas GLS in normal subjects with high and low HR was similar (20.3 ± 1.7% vs. 20.3 ± 2.0%; P = 0.99). Multivariable logistic regression analysis showed that high HR (odds ratio: 1.04; 95% confidence interval: 1.01–1.07; P = 0.01) was independently associated with GLS < 18% in T2DM patients as well as HbA1c, T2DM duration, LVEF, body mass index, and mitral inflow E and mitral e’ annular velocity ratio. One sequential logistic model evaluating the associations between GLS < 18% and clinical variables in T2DM patients showed an improvement with the addition of LVEF and E/e’ (P < 0.001) and a further improvement with the addition of high HR (P < 0.001). Conclusion Compared with normal subjects, resting HR was associated with LV longitudinal myocardial function in asymptomatic T2DM patients with preserved LVEF. Our findings provide new insights on the management of T2DM patients.

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In the Loop—Left Ventricular Pressures

Just Enough Physiology ◽

10.1093/med/9780199797790.003.0005 ◽

2011 ◽

pp. 42-47

Author(s):

James R. Munis

Keyword(s):

Heart Rate ◽

Cardiac Output ◽

Aortic Valve ◽

Left Ventricle ◽

Stroke Volume ◽

Cardiovascular System ◽

Aortic Root ◽

Left Ventricular ◽

Root Pressure ◽

The Third

We've already looked at 2 types of pressure that affect physiology (atmospheric and hydrostatic pressure). Now let's consider the third: vascular pressures that result from mechanical events in the cardiovascular system. As you already know, cardiac output can be defined as the product of heart rate times stroke volume. Heart rate is self-explanatory. Stroke volume is determined by 3 factors—preload, afterload, and inotropy—and these determinants are in turn dependent on how the left ventricle handles pressure. In a pressure-volume loop, ‘afterload’ is represented by the pressure at the end of isovolumic contraction—just when the aortic valve opens (because the ventricular pressure is now higher than aortic root pressure). These loops not only are straightforward but are easier to construct just by thinking them through, rather than by memorization.

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Effect of peripheral cardiopulmonary bypass on left ventricular size, afterload and myocardial function during elective supported coronary angioplasty

Journal of the American College of Cardiology ◽

10.1016/0735-1097(91)90606-a ◽

1991 ◽

Vol 18 (2) ◽

pp. 499-505 ◽

Cited By ~ 23

Author(s):

Gregory S. Pavlides ◽

Andrew M. Hauser ◽

Robert K. Stack ◽

Patricia I. Dudlets ◽

Cindy Grines ◽

...

Keyword(s):

Cardiopulmonary Bypass ◽

Coronary Angioplasty ◽

Myocardial Function ◽

Left Ventricular ◽

Ventricular Size ◽

Left Ventricular Size

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Short-Time Impact of Laser Ablation of Placental Anastomoses on Myocardial Function in Monochorionic Twins with Twin-to-Twin Transfusion Syndrome

Ultraschall in der Medizin - European Journal of Ultrasound ◽

10.1055/s-0035-1553405 ◽

2015 ◽

Vol 38 (04) ◽

pp. 403-410 ◽

Cited By ~ 3

Author(s):

Jan Degenhardt ◽

Meike Reinold ◽

Christian Enzensberger ◽

Aline Wolter ◽

Andrea Kawecki ◽

...

Keyword(s):

Laser Ablation ◽

Left Ventricle ◽

Myocardial Function ◽

Statistical Significance ◽

Left Ventricular ◽

Left Ventricular Ejection ◽

Tei Index ◽

Ejection Time ◽

Monochorionic Twins ◽

Ventricular Ejection Time

Abstract Purpose To evaluate pre- and post-procedure myocardial function in monochorionic twins with TTTS who underwent laser ablation of placental anastomoses using pulsed wave tissue Doppler imaging (pw TDI). Materials and Methods 20 monochorionic twin gestations with TTTS were included and underwent laser ablation at our center between 2011 and 2014. Prior to and after the intervention, cardiac function was assessed by measuring the mitral annular plane systolic excursion (MAPSE), the tricuspid annular plane systolic excursion (TAPSE), Tei index, isovolumetric contraction time (ICT), ejection time (ET), isovolumetric relaxation time (IRT) for the left ventricle in pulsed wave Doppler (pw D) ultrasound as well as ICT, ET, IRT and Tei index in pw TDI for the left and right ventricle. E-, A-, E´- and A´-wave peak velocity and the systolic downward motion (S´) were measured for both ventricles and the E/A, E/E´ and E´/A´ ratios were calculated. In a mean of 1.3 (SD 0.6) days after laser ablation, this measurement protocol was repeated. Results Pre-intervention recipients had longer ICT, ET and IRT in pw D and pw TDI compared to donors not reaching statistical significance for most parameters. Statistically significant were prolonged ICT in pw D (p 0.01) and ET (p 0.01) in pw TDI in recipients. In donor fetuses preoperative myocardial function did not differ significantly from postoperative myocardial function except in increased left ventricular ejection time of the left ventricle in pw TDI (p 0.04) and an increased E´/A´ratio (p 0.01). After laser coagulation, myocardial function was slightly altered in recipients as ICT and IRT shortened and Tei indices decreased but only reaching statistical significance in shortened IRTs in pw TDI for both ventricles. Conclusion Laser ablation of placental anastomoses in TTTS might influence myocardial function in the postoperative period. Shortened IRT intervals may reflect an improvement of diastolic function in recipients.

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Echocardiographic assessment of the impact of percutaneous revascularisation of chronic total occlusion on myocardial function and electrical stability, two-year follow up period

European Heart Journal ◽

10.1093/ehjci/ehaa946.0134 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

O Petrovic ◽

S Juricic ◽

N Arnautovic ◽

I Paunovic ◽

D Trifunovic-Zamaklar ◽

...

Keyword(s):

Chronic Total Occlusion ◽

Longitudinal Strain ◽

Myocardial Function ◽

Left Ventricular ◽

Electrical Stability ◽

Predictive Tool ◽

Total Occlusion ◽

Mechanical Dispersion ◽

The Impact

Abstract Background Chronic total coronary occlusion (CTO) is frequent finding in patients with ischaemic heart disease, but it is not clear yet how it affects myocardial function, especially electrical stability. Myocardial strain by echocardiography can objectively quantify extent and timing of myocardial deformation. Echocardiographically derived dyssynchrony, mechanical dispersion, is good predictive tool for patients at risk of ventricular arrhythmias. Purpose The purpose of this study was to evaluate the influence of chronic total occlusion percutaneous coronary intervention (CTO PCI) on myocardial contractility and arrhythmogenicity. Methods We analysed total of 35 CTO patients (age 56±9, 86% male). Convectional echocardiographic exam with two dimensional speckle tracking echocardiography (2D STE) was performed before CTO PCI and after 24 months of follow-up. Peak longitudinal strain was assessed in 17 left ventricular segments. 2D STE computed global longitudinal strain (GLS). Time intervals from start of Q/R on electrocardiogram to peak negative strain during the cardiac cycle were assessed. Mechanical dispersion was defined as the standard deviation of this time interval from 17 left ventricular segments, reflecting myocardial contraction heterogeneity. Results 24 months after CTO PCI patients showed no change in ejection fraction (EF) (55.75±7.56% vs. 56.03±6.29%, p=0.622). There was slight improvement in GLS (−14.89±2.81% vs. −15.93±2.64%, p<0.05), Mechanical dispersion was significantly reduced (62.78±23.44ms vs 47.96±12.10ms, p<0.001) Conclusion CTO recanalization improved GLS without changes in left ventricular EF after 24 months. Mechanical dispersion as a surrogate for arrhythmogenic substrate was reduced by CTO PCI. Funding Acknowledgement Type of funding source: None

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Cardiac function in goats exposed to carbon monoxide

Journal of Applied Physiology ◽

10.1152/jappl.1979.47.2.429 ◽

1979 ◽

Vol 47 (2) ◽

pp. 429-434 ◽

Cited By ~ 6

Author(s):

W. E. James ◽

C. E. Tucker ◽

R. F. Grover

Keyword(s):

Heart Rate ◽

Carbon Monoxide ◽

Cardiac Index ◽

Sympathetic Activity ◽

Myocardial Function ◽

Statistical Significance ◽

Hemoglobin Concentration ◽

Ventricular Myocardium ◽

Left Ventricular ◽

Left Ventricular Myocardium

To investigate the possibility that prolonged carbon monoxide (CO) exposure would depress myocardial function, six chronically instrumented, unsedated goats were exposed to 160--200 ppm CO for 2 wk, resulting in a mean carboxyhemoglobin saturation of 20%. Cardiac index and stroke volume remained unchanged during and after exposure. Hematocrit and hemoglobin concentration started increasing on the 10th day of exposure, this increase reached statistical significance (P less than 0.05) on the 6th postexposure day. Contractility (Vmax) of the left ventricular myocardium and heart rate were unchanged during exposure to CO, but both were significantly (P less than 0.05) decreased at some time during the 1st wk after removal from CO. If there was a decrease in intrinsic myocardial function during CO exposure, it may have been masked by increased sympathetic activity. The mechanism(s) that might produce the decrease in heart rate and contractility after removal from CO are not obvious. Possible explanations are discussed.

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