Global left ventricular electromechanical dyssynchrony (GLVD) is uncoordinated LV contraction that reduces the extent of intrinsic energy transfer from the myocardium to the circulation leading to a reduction in peak LV pressure rise, prolonged total isovolumic time (t-IVT) and fall in stroke volume . This potentially important parameter is not routinely assessed in critically ill cardiothoracic patients.
A prospective analysis of retrospectively collected data in cardiothoracic ICU patients who underwent echocardiography was performed. In addition to epidemiological factors, echo data included comprehensive assessment of LV/RV systolic and diastolic function including Doppler analysis of isovolumic contraction/ relaxation, ejection time (ET) and filling time (FT). t-IVT was calculated as (60 - (total ET + total FT)) and the Tei Index as (ICT + IRT) / ET. t-IVT >14 second/minute and Tei index >0.48 were used to define GLVD . Data are shown as mean ± SD/median (interquartile range).
A total of 103 patients (63.5 ± 18.4 years), 65 male (63%), APACHE II score (14.6 ± 7.4) were included. The prevalence of GLVD was high (24/103, 22%) and associated with significantly increased mortality, 7.5% vs. 25% (P = 0.02). There was no difference in requirement for cardiorespiratory support between the two populations, but there were significant differences (no GLVD vs. GLVD) in requirement for pacing (35% vs. 62%, P = 0.02), atrial fibrillation (20% vs. 41%, P = 0.03), QRS duration (92.0 (80.0 to 120.0) vs. 116.5 (95.0 to 154.0), P = 0.01) and QTc (460.0 (416.0 to 498.5) vs. 477.5 (451.2 to 541.0), P = 0.02). There was no significant difference in ejection fraction (no GLVD 43.0 (35.0 to 49.5) vs. GLVD 39.6 (29.5 to 49.7), P = 0.43), mitral regurgitation (40.5% vs. 62.5%, P = 0.06), or any other measures of LV systolic or diastolic function between the two groups. There was good correlation between the two methods used to assess dyssynchrony (LV t-IVT:LV Tei index correlation coefficient = 0.80, P <0.001).
GLVD that limits cardiac output is common in the cardiothoracic ICU, and significantly related to mortality. When diagnosed, the underlying cause should be sought and treatment instigated to minimize the t-iVT (pacing optimization/revascularization/ inotrope titration/volaemia optimization).