Background-We validated the clinical relevance of ventricular stiffness by examining surgical morbidity in children with univentricular hearts undergoing Fontan operation. We hypothesized that ventricular stiffness affects Fontan morbidity, particularly duration of pleural effusions. Methods and Results-Sixteen children with right ventricular (RV) (n ϭ11) or left ventricular (LV) (n ϭ5) dominance were studied intraoperatively at a median age of 3.3 years (1.8 to 5.1). Transesophageal long-axis echocardiograms and ventricular pressure by micromanometer provided end-diastolic pressure (P) area (A) relations during initiation and conclusion of cardiopulmonary bypass. Curve fitting to the equation Pϭ␣e ␤A defined the ventricular stiffness constant, ␤. Changes in ␤ and clinical correlations were examined. Ventricular stiffness increased after bypass in patients with complete pre-bypass and post-bypass data (n ϭ11, Pϭ0.023, mixed models methodology). Pre-bypass ␤ correlated well with duration of chest tube (CT) drainage (rϭ0.90, n ϭ16), net perioperative fluid balance (rϭ0.71, nϭ14), and length of stay (LOS) (rϭ0.81, n ϭ16). CT duration and LOS also correlated significantly with post-bypass ␤ (rϭ0.77 for both, nϭ11), but insignificantly with preoperative catheterization pressures. Conclusions-Intraoperative

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Left ventricular pacing site and right ventricular-left ventricular delay can be optimized with a multielectrode patch and randomized data collection. This technique can be used further in clinical studies.

Optimization of left ventricular pacing site (LVPS) or interventricular pacing delay (VVD) improves the efficacy of biventricular pacing (BiVP). Cardiac output (CO) based optimization, however, is invasive and slow. QRS duration (QRSd) is non-invasive and responds rapidly. Accordingly, we investigated the utility of QRSd for BiVP optimization in a model of acute right ventricular (RV) pressure overload. In 7 anesthetized open-chest pigs, BiVP was implemented with right atrial and RV pacing wires. A 6-electrode array was placed behind the LV. Heart block was established by alcohol ablation. The pulmonary artery was snared to double peak RV pressure. Fifty-four combinations of LVPS and VVD were tested in random order over 30 sec intervals. QRSd was assessed from ECG lead II, CO from aortic flow probe, and ventricular function from micromanometers. Comparisons were made with the Pearson’s correlation coefficient (r). QRSd narrowing was associated with improved RV function and transseptal synchrony, but correlation with CO was poor. Additionally, QRSd averaged over the last 20 cardiac cycles in each interval was compared to values averaged over successive cardiac cycles following each reprogramming. Seven cardiac cycles after reprogramming, the average r-value went above 0.90 and plateaued. QRSd-based optimization merits further study during BiVP in patients with congestive heart failure.

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