Comprehensive use of cardiac computed tomography to guide left ventricular lead placement in cardiac resynchronization therapy

Abstract

Background: Optimal lead positioning is an important determinant of cardiac resynchronization therapy (CRT) response.

Objective: The purpose of this study was to evaluate cardiac computed tomography (CT) selection of the optimal epicardial vein for left ventricular (LV) lead placement by targeting regions of late mechanical activation and avoiding myocardial scar.

Methods: Eighteen patients undergoing CRT upgrade with existing pacing systems underwent preimplant electrocardiogram-gated cardiac CT to assess wall thickness, hypoperfusion, late mechanical activation, and regions of myocardial scar by the derivation of the stretch quantifier for endocardial engraved zones (SQUEEZ) algorithm. Cardiac venous anatomy was mapped to individualized American Heart Association (AHA) bull's-eye plots to identify the optimal venous target and compared with acute hemodynamic response (AHR) in each coronary venous target using an LV pressure wire.

Results: Fifteen data sets were evaluable. CT-SQUEEZ-derived targets produced a similar mean AHR compared with the best achievable AHR (20.4% ± 13.7% vs 24.9% ± 11.1%; P = .36). SQUEEZ-derived guidance produced a positive AHR in 92% of target segments, and pacing in a CT-SQUEEZ target vein produced a greater clinical response rate vs nontarget segments (90% vs 60%).

Conclusion: Preprocedural CT-SQUEEZ-derived target selection may be a valuable tool to predict the optimal venous site for LV lead placement in patients undergoing CRT upgrade.

Keywords: CT guided intervention; Cardiac computed tomography; Cardiac resynchronization therapy; Dyssynchrony; Myocardial fibrosis.

Graphical abstract

Figure 1

A: Computed tomography mid-ventricular short-axis images of the left ventricle at 2 time points in the R-R interval (0% = end diastole; 50% = end systole). Anterior and anteroseptal regions are akinetic and seen not to move throughout the cardiac cycle compared with the inferolateral segments that move inward by end systole. Inevitable beam hardening artifact from the existing pacing system noted in the right ventricle. B: Stretch quantifier for endocardial engraved zones values (y axis) vs cardiac cycle length (%) across 16 AHA segments demonstrate akinetic regions (red box) and late activating inferior/inferolateral walls (green box representing an ideal target for left ventricular lead placement).

Figure 2

A: Bull’s-eye plot of the time delay (color scale, in milliseconds) until 10% shortening occurs (ie, time for SQUEEZ value to reduce from 1.0 to 0.9) across left ventricular regions. Dark red/brown shows anterior and anteroseptal segments not achieving 10% shortening and likely represents infarcted myocardium. The outlined red box represents areas to avoid (akinetic segments). Red-colored regions in the inferolateral wall show the latest activation away from areas of scar; the outlined green box shows the target pacing regions. B: Bull’s-eye plot with color scale representing SQUEEZ values. All segments begin at a SQUEEZ value of 1. Yellow represents a SQUEEZ value of >1 (paradoxical stretch/dyskinesis in septal regions). Blue represents a SQUEEZ value of <0.8, and viable regions with reasonable shortening deemed as good targets. SQUEEZ = stretch quantifier for endocardial engraved zones.

Figure 3

Left: Occlusive venography with nomenclature for the coronary venous tree. Reproduced with permission from Spencer et al.Right: Regional acute hemodynamic response by coronary vein tested. Box-and-whisker plot for each vein detailing the mean (solid line), range, and SD. Acute hemodynamic response values are % change in dP/dt vs baseline. There was a significant difference between groups: P = .001 (ANOVA). AIV = anterior interventricular vein; ANOVA = analysis of variance; CS = coronary sinus; LAO = left anterior oblique; MCV = middle cardiac vein.

Figure 4

Percentage change AHR determined by pacing the vein with optimal AHR per patient (Best, n = 14), the CT-SQUEEZ–derived target (CT target, n = 12), greatest electrical latency (Longest QLV, n = 13), absence of scar (Out of scar, n = 14), presence of scar (In scar, n = 6), and the vein with the worst AHR per patient (Worst, n = 14). Best vs CT target, P = .36; Best vs Longest QLV, P = .22; Best vs Out of scar, P = .03; Best vs In scar, P = .002; Best vs Worst, P = .0002; CT target vs Longest QLV, P = .85; CT target vs Out of scar, P = .29; CT target vs In scar, P = .04; CT target vs Worst, P = .009. AHR = acute hemodynamic response; CT = computed tomography; SQUEEZ = stretch quantifier for endocardial engraved zones.

Figure 5

Scatterplot of AHR vs QLV interval. Each patient had multiple data points acquired. There is a weak correlation between AHR and QLV interval (r = 0.31; P = .01). Locations in scar (red) had a lower AHR than did locations out of scar (blue). AHR = acute hemodynamic response.

Figure 6

Clinical response rates in CT-SQUEEZ target (n = 10) vs nontarget (n = 5) (P < .001) and ICM (n = 8) vs NICM (n = 10) (P = .07). CT = computed tomography; ICM = ischemic cardiomyopathy; NICM = nonischemic cardiomyopathy; SQUEEZ = stretch quantifier for endocardial engraved zones.