Optimized temporary biventricular pacing acutely improves intraoperative cardiac output after weaning from cardiopulmonary bypass: A substudy of a randomized clinical trial

Abstract

Objective Permanent biventricular pacing benefits patients with heart failure and interventricular conduction delay, but the importance of pacing with and without optimization in patients at risk of low cardiac output after heart surgery is unknown. We hypothesized that pacing parameters independently affect cardiac output. Accordingly, we analyzed aortic flow measured with an electromagnetic flowmeter in patients at risk of low cardiac output, during an ongoing randomized clinical trial of biventricular pacing (n=11) vs. standard of care (n=9). Methods A sub-study was conducted in all 20 patients, in both groups, with stable pacing after coronary artery bypass grafting and/or valve surgery. Ejection fraction averaged 33±15%, QRS duration 116±19 msec. Effects were measured within one hour of the conclusion of cardiopulmonary bypass. Atrioventricular delay (7 settings) and interventricular delay (9 settings) were optimized in random sequence. Results Optimization of atrioventricular delay (171±8 msec), at an interventricular delay of 0 msec, increased flow 14% vs. the worst setting (111±11 msec, p < 0.001) and 7% vs. nominal atrioventricular delay (120 msec, p < 0.001). Interventricular delay optimization increased flow 10% vs. the worst setting (p < 0.001) and 5% vs. nominal interventricular delay (0 msec, p < 0.001). Optimized pacing increased cardiac output 13% vs. atrial pacing at matched heart rate (5.5±0.5 vs. 4.9±0.6 L/min; p = 0.003) and 10% vs. sinus rhythm (5.0±0.6 L/min; p = 0.019). Conclusions Temporary biventricular pacing increases intraoperative cardiac output in patients with left ventricular dysfunction undergoing cardiac surgery. Atrioventricular and interventricular delay optimization maximizes this benefit.

Case 10–2015

“…The randomized biventricular pacing after cardiac surgery (BIPACS) trial investigated multisite pacing after cardiac surgery to determine if an optimized pacing protocol could increase cardiac index in the immediate postoperative period. 13 Although the study was discontinued because of slow enrollment and inability to demonstrate efficacy of the primary outcome, a subset of data was published from 20 patients. Optimized biventricular pacing increased cardiac output by 13% and 10% compared with AAI pacing and sinus rhythm, respectively, in the immediate period after cardiopulmonary bypass.…”

“…12 These patients also may benefit from temporary biventricular pacing to improve cardiac function in the immediate postoperative period. 13 Access to the entire heart gives the surgeon the ability to place the LV lead in the most optimal position based on preoperative and intraoperative studies. This technique, apart from offering the option of placing the lead in the most optimal anatomic location, allows recognition of local scar, which is a major impediment to achieving optimal capture thresholds.…”

Entraînement électrosystolique épicardique temporaire post-chirurgie cardiaque : modalités pratiques

“…L'amé lioration du dé bit cardiaque né cessite l'optimisation des paramè tres et des modalité s d'entraînement é lectrosytolique (mode DDD ou AAI en l'absence de troubles de la conduction, optimisation du dé lai AV et de la FC) [1,6]. En cas de dé faillance systolique ventriculaire gauche sé vè re avec QRS é largi, l'inté rêt de la stimulation atriobiventriculaire à l'aide d'é lectrodes é picardiques temporaires a é té prouvé par plusieurs é tudes, à l'instar de la resynchronisation interventriculaire permanente [7,8].…”

“…Le dé lai AV optimal devrait être recherché pour assurer le synchronisme « parfait » entre les oreillettes et les ventricules, c'est-à -dire é viter la contraction atriale quand les valves AV sont fermé es et la contraction ventriculaire quand elles sont ouvertes [1]. Classiquement, la valeur du dé lai AV ré glé e par dé faut sur les stimulateurs externes est de 150 ms pour une fré quence de 90 b/ min, mais cette valeur peut sous-estimer le dé lai AV optimal, surtout en cas de cardiopathie dilaté e. Dans une é tude portant sur l'optimisation de l'EES atriobiventriculaire chez les patients ayant une FEVG infé rieure ou é gale à 40 %, Wang et al [8] montraient que le dé lai AV correspondant au meilleur dé bit cardiaque é tait de 171 ms. L'ajustement manuel de ce dé lai AV par titration et avec mesure simultané e du dé bit cardiaque pourrait ainsi optimiser l'é tat hé modynamique sans augmentation supplé mentaire de la consommation myocardique en oxygè ne ; PVARP : repré sente la pé riode suivant la contraction ventriculaire pendant laquelle le canal atrial du stimulateur sera en pé riode ré fractaire, c'est-à -dire qu'il ne va pas dé clencher de nouvelle stimulation é lectrique. Seulement aprè s cette pé riode, une nouvelle dé polarisation atriale endogè ne dé tecté e pourra entraîner un spike ventriculaire.…”

Clinical Review: Management of weaning from cardiopulmonary bypass after cardiac surgery

“…Various modes of biventricular or atrial pacing can reduce ventricular dyssynchrony and might improve mechanical efficiency of cardiac contraction (about 14% increase in SV) without increasing myocardial oxygen consumption. [81] Evidence of myocardial ischemia (e.g., ST segment abnormalities, new/worsening LV/RV wall motion abnormalities) may justify the need for further myocardial revascularization (ST segment elevation, transmural ischemia) or the infusion of nitroglycerine (ST segment depression, subendocardial ischemia). However, limitations in the interpretation of regional wall motion abnormalities should be considered since they have also been reported in case of hypovolemic states, conduction abnormalities (bundle branch block, ventricular pacing), and myocardial stunning.…”