Prediction of interatrial and interventricular electromechanical delays from P/QRS measurements: value for pacemaker timing optimization

Summary: Cardiac pacing creates spurious delays between and within the cardiac chambers. These are: 1. Left atrial (LA) transport delay (ATD) either sensed (s) or paced (p), (time from right atrial P-wave to the end of LA transport (mitral Doppler A-wave)). 2. Interventricular delay (IVD), (time from onsets of right (RV) to left ventricular (LV) contractions). 3. P-sense offset (PSO), (time from P-onset to P-detection). Thus, restoration of left heart atrioventricular (AV) synchrony can be accomplished by compensating above delays, according to a previously published equation: RAV = ATD-IVD-PSO, where RAV = right heart AV.
Objective: To test the hypothesis that ATD could be predicted from Ps and Pp, and that interventricular delay (IVD) could be predicted from QRSp, using three-lead surface electrocardiograms (ECGs).
Methods: Thirty-six patients aged 63.5 ± 15.5 years, 64% males, all with previously implanted DDD pacemakers, were studied by echo-Doppler and surface ECG obtained with a pacemaker programmer. Measurements included Ps; Pp; intrinsic QRSs; and paced QRSp, ATDs, ATDp, and IVD (difference between RVp and RVs left preejection intervals, PEI). Regressions between ECG and echo-Doppler intervals were calculated.
Results: Regressions and correlation coefficients: ATD (s+p) = 0.96*P + 55 (R = 0.94, P < 0.0001); PEIp = 0.75 * QRSp + 34.8 (R = 0.89, P< 0.0001); IVD = 0.39 *QRSp – 7.9 ms (R = 0.87, P = 0.002).
Conclusions: Inter-atrial and inter-ventricular electromechanical delays can be predicted from P-wave and QRS durations. These measurements allow AV delay optimization in DDD and cardiac resynchronization therapy devices with no need of Doppler echocardiography.     

Interatrial conduction correlates with optimal atrioventricular timing in cardiac resynchronization therapy devices

Background: Echocardiographic optimization of the atrioventricular delay (AV) may result in improvement in cardiac resynchronization therapy (CRT) outcome. Optimal AV has been shown to correlate with interatrial conduction time (IACT) during right atrial pacing. This study aimed to prospectively validate the correlation at different paced heart rates and examine it during sinus rhythm (Sinus). Methods: An electrophysiology catheter was placed in the coronary sinus (CS) during CRT implant (n = 33). IACT was measured during Sinus and atrial pacing at 5 beats per minute (bpm) and 20 bpm above the sinus rate as the interval from atrial sensing or pacing to the beginning of the left atrial activation in the CS electrogram. P‐wave duration (PWd) was measured from 12‐lead surface electrocardiogram, and the interval from the right atrial to intrinsic right ventricular activation (RA‐RV) was measured from device electrograms. Within 3 weeks after the implant patients underwent echocardiographic optimization of the sensed and paced AVs by the mitral inflow method. Results: Optimal sensed and paced AVs were 129 ± 19 ms and 175 ± 24 ms, respectively, and correlated with IACT during Sinus (R = 0.76, P < 0.0001) and atrial pacing (R = 0.75, P < 0.0001), respectively. They also moderately correlated with PWd (R = 0.60, P = 0.0003 during Sinus and R = 0.66, P < 0.0001 during atrial pacing) and RA‐RV interval (R = 0.47, P = 0.009 during Sinus and R = 0.66, P < 0.0001 during atrial pacing). The electrical intervals were prolonged by the increased atrial pacing rate. Conclusion: IACT is a critical determinant of the optimal AV for CRT programming. Heart rate‐dependent AV shortening may not be appropriate for CRT patients during atrial pacing. (PACE 2011; 34:443–449)     

Pulmonary artery diameter: means and normal limits—assessment by computed tomography angiography

Open in a separate window OBJECTIVESNormal pulmonary artery (PA) diameter remains blurred and the definitions of PA aneurysm are heterogenous. We aimed to assess PA diameters, identify a threshold for normal diameters, define PA aneurysms, possible predictors of PA size and evaluate the correlation with mid-ascending aortic diameters.METHODSBetween April 2018 and August 2019, 497 consecutive patients who underwent whole-body computed tomographic angiography were reviewed. Clinical and imaging data were collected from our institutional database. Precise three-dimensional centreline measurements were taken. Linear regression analysis was performed to detect parameters associated with PA diameter. A two-stage model was created to identify potential predictors and the resulting statistically significant interactions were tested. Data were grouped and PA, standard deviation, and upper normal limits were calculated.RESULTSAmong 497 patients with an average age of 51.4 (20.2) (74.6% males), the mean PA diameter measured 32.0 (4.6) mm [female: 31.2 (4.7) mm vs male: 32.2 (4.5) mm; P = 0.032]. The mean PA length, left PA and right PA diameters were similar between male and female patients. We found a significant correlation (r = 0.352; P < 0.001) between the PAs and mid-ascending aortic diameters. Body surface area (P = 0.032, β =  4.52 [0.40; 8.64] 95% CI) was the only significant influencing variable for PA diameter.CONCLUSIONSThe normal mean PA diameter in a reference cohort is 32.0 (4.6) mm. Body surface area is the only influencing variable of PA diameter. The normal diameters measured and corresponding upper limits of normal revealed that a PA aneurysm should not be considered below a threshold of 45 mm.