Design of an Acute dP/dt Hemodynamic Measurement Protocol to Isolate Cardiac Effect of Pacing

Pacing Optimized by Left Ventricular dP/dtmax

Left ventricular (LV) dP/dt_max provides a sensitive measure of the acute hemodynamic response to cardiac resynchronization therapy (CRT) and can predict reverse remodeling on echocardiography. Its use to guide LV lead placement has been shown to improve outcomes in a multicenter randomized trial. Given the invasive protocol required for measurement, it is unlikely to be universally beneficial for patients undergoing CRT but may be useful for patients who do not respond to conventional CRT, or in those who have borderline indications or risk factors for non-response. In such cases, LV dP/dt_max may help guide LV lead placement, optimize device programming, and select the best alternative method of delivering CRT, such endocardial LV pacing or conduction system pacing.

Benefits of Multisite/Multipoint Pacing to Improve Cardiac Resynchronization Therapy Response

This article provides a general overview of the underlying mechanisms that support pacing from more discrete points and/or a wider vector (multisite and multipoint pacing) to improve left ventricular resynchronization. We performed a critical overview of the current literature and to identify some remaining knowledge gaps to spur further research. It was not our goal to provide a systematic review with a comprehensive bibliography, but rather to focus on selected publications that, in our opinion, have either expertly reviewed a specific aspect of cardiac resynchronization therapy or have been landmark studies in the field.

Long-term reverse remodeling by cardiac resynchronization therapy with MultiPoint Pacing: A feasibility study of noninvasive hemodynamics-guided device programming

BACKGROUND

Cardiac resynchronization therapy (CRT) with multipoint left ventricular (LV) pacing (MultiPoint Pacing [MPP]) improves acute hemodynamics and chronic outcomes in comparison to conventional biventricular pacing (BiV), though MPP programming questions persist.

OBJECTIVES

In this multicenter feasibility study, we evaluated the feasibility of using noninvasive systolic blood pressure (SBP) to guide MPP programming and assessed the chronic 6-month echocardiographic CRT response.

METHODS

Patients implanted with MPP-enabled CRT-defibrillator devices underwent noninvasive hemodynamic assessment (finger arterial pressure) during a pacing protocol that included atrial-only pacing and various BiV and MPP configurations. Each configuration was repeated 4 times, alternating with a reference pacing configuration, to calculate the SBP difference relative to reference (ΔSBP). CRT configurations with the greatest ΔSBP were programmed. An independent core laboratory analyzed baseline and 6-month echocardiograms, with CRT response defined as a 6-month reduction in LV end-systolic volume ≥ 15%.

RESULTS

Forty-two patients (71% male; LV ejection fraction 30.3% ± 7.5%; QRS duration 161 ± 19 ms; 26% had ischemic cardiomyopathy) were enrolled in 4 European centers. Relative to atrial-only pacing, the best BiV and best MPP configurations produced significant SBP elevations of 3.1 ± 4.2 (P < .01) and 4.1 ± 4.1 mm Hg (P < .01), respectively (BiV vs MPP; P < .01). Greater SBP elevations were associated with the best MPP compared with the best BiV configurations in 29 of 37 patients completing the pacing protocol (78%). Of MPP-programmed patients completing the 6-month follow-up visit, 23 of 27 (85%) were classified as CRT responders (6-month reduction in LV end-systolic volume 37.0% ± 13.6%).

CONCLUSION

Acute noninvasive hemodynamics after CRT device implantation predominantly favored MPP over BiV programming. MPP programming guided by noninvasive hemodynamics resulted in positive LV structural remodeling.

Improved patient selection for cardiac resynchronization therapy by normalization of QRS duration to left ventricular dimension

Aims

This study evaluates the relative importance of two components of QRS prolongation, myocardial conduction velocity and travel distance of the electrical wave front (i.e. path length), for the prediction of acute response to cardiac resynchronization therapy (CRT) in left bundle branch block (LBBB) patients.

Methods and results

Thirty-two CRT candidates (ejection fraction <35%, LBBB) underwent cardiac magnetic resonance (CMR) imaging to provide detailed information on left ventricular (LV) dimensions. Left ventricular end-diastolic volume (LVEDV) was used as a primary measure for path length, subsequently QRSd was normalized to LV dimension (i.e. QRSd divided by LVEDV) to adjust for conduction path length. Invasive pressure-volume loop analysis at baseline and during CRT was used to assess acute pump function improvement, expressed as LV stroke work (SW) change. During CRT, SW improved by +38 ± 46% (P < 0.001). The baseline LVEDV was positively related to QRSd (R = 0.36, P = 0.044). Despite this association, a paradoxical inverse relation was found between LVEDV and SW improvement during CRT (R = -0.40; P = 0.025). Baseline unadjusted QRSd was found to be unrelated to SW changes during CRT (R = 0.16; P = 0.383), whereas normalized QRSd (QRSd/LVEDV) yielded a strong correlation with CRT response (R = 0.49; P = 0.005). Other measures of LV dimension, including LV length, LV diameter, and LV end-systolic volume, showed similar relations with normalized QRSd and SW improvement.

Conclusion

Since normalized QRSd reflects myocardial conduction properties, these findings suggest that myocardial conduction velocity rather than increased path length mainly determines response to CRT. Normalizing QRSd to LV dimension might provide a relatively simple method to improve patient selection for CRT.

Hemodynamic comparison of different multisites and multipoint pacing strategies in cardiac resynchronization therapies

PURPOSE

In order to increase the responder rate to CRT, stimulation of the left ventricular (LV) from multiple sites has been suggested as a promising alternative to standard biventricular pacing (BIV). The aim of the study was to compare, in a group of candidates for CRT, the effects of different pacing configurations-BIV, triple ventricular (TRIV) by means of two LV leads, multipoint (MPP), and multipoint plus a second LV lead (MPP + TRIV) pacing-on both hemodynamics and QRS duration.

METHODS

Fifteen patients (13 male) with permanent AF (mean age 76 ± 7 years; left ventricular ejection fraction 33 ± 7%; 7 with ischemic cardiomyopathy; mean QRS duration 178 ± 25 ms) were selected as candidates for CRT. Two LV leads were positioned in two different branches of the coronary sinus. Acute hemodynamic response was evaluated by means of a RADI pressure wire as the variation in LVdp/dtmax.

RESULTS

Per patient, 2.7 ± 0.7 veins and 5.2 ± 1.9 pacing sites were evaluated. From baseline values of 998 ± 186 mmHg/s, BIV, TRIV, MPP, and MPP-TRIV pacing increased LVdp/dtmax to 1200 ± 281 mmHg/s, 1226 ± 284 mmHg/s, 1274 ± 303 mmHg, and 1289 ± 298 mmHg, respectively (p < 0.001). Bonferroni post-hoc analysis showed significantly higher values during all pacing configurations in comparison with the baseline; moreover, higher values were recorded during MPP and MPP + TRIV than at the baseline or during BIV and also during MPP + TRIV than during TRIV. Mean QRS width decreased from 178 ± 25 ms at the baseline to 171 ± 21, 167 ± 20, 168 ± 20, and 164 ± 15 ms, during BIV, TRIV, MPP, and MPP-TRIV, respectively (p < 0.001).

CONCLUSIONS

In patients with AF, the acute response to CRT improves as the size of the early activated LV region increases.

Validation of a defibrillation lead ventricular volume measurement compared to three-dimensional echocardiography

BACKGROUND

There is increasing evidence that using frequent invasive measures of pressure in patients with heart failure results in improved outcomes compared to traditional measures. Admittance, a measure of volume derived from preexisting defibrillation leads, is proposed as a new technique to monitor cardiac hemodynamics in patients with an implantable defibrillator.

OBJECTIVE

The purpose of this study was to evaluate the accuracy of a new ventricular volume sensor (VVS, CardioVol) compared with 3-dimenssional echocardiography (echo) in patients with an implantable defibrillator.

METHODS

Twenty-two patients referred for generator replacement had their defibrillation lead attached to VVS to determine the level of agreement to a volume measurement standard (echo). Two opposite hemodynamic challenges were sequentially applied to the heart (overdrive pacing and dobutamine administration) to determine whether real changes in hemodynamics could be reliably and repeatedly assessed with VVS. Equivalence of end-diastolic volume (EDV) and stroke volume (SV) determined by both methods was also assessed.

RESULTS

EDV and SV were compared using VVS and echo. VVS tracked expected physiologic trends. EDV was modulated -10% by overdrive pacing (14 mL). SV was modulated -13.7% during overdrive pacing (-6 mL) and increased over baseline +14.6% (+8 mL) with dobutamine. VVS and echo mean EDVs were found statistically equivalent, with margin of equivalence 13.8 mL (P <.05). Likewise, mean SVs were found statistically equivalent with margin of equivalence 15.8 mL (P <.05).

CONCLUSION

VVS provides an accurate method for ventricular volume assessment using chronically implanted defibrillator leads and is statistically equivalent to echo determination of mean EDV and SV.

16 Years of Cardiac Resynchronization Pacing Among Congenital Heart Disease Patients: Direct Contractility (dP/dt-max) Screening When the Guidelines Do Not Apply

OBJECTIVES

The purpose of this study was to use direct cardiac resynchronization therapy (CRT)-paced contractility (dP/dt-max) response as a pre-implantation evaluation among patients with congenital heart disease (CHD) and follow clinical parameters and contractility indexes after CRT implantation.

BACKGROUND

Patients with CHD often develop early heart failure with few therapeutic options, leading to heart transplantation (HT). Unfortunately, guidelines for CRT do not apply, and function evaluations by cardiac ultrasound are often inaccurate among CHD anatomies. Therefore, which CHD patients would benefit from CRT remains an enigma.

METHODS

From 1999 to 2015, 103 CHD patients with New York Heart Association (NYHA) functional class II to IV were listed for HT; 40 patients on optimal medical therapy were referred for paced contractility response cardiac catheterization before CRT consideration. If dP/dt-max improved ≥15% from baseline, these "responders" were given the option of CRT with continued follow-up after implantation.

RESULTS

Of 40 patients studied, 26 (65%) (age 22 ± 8.2 years; 9 of 26 [35%] single or systemic right ventricle; 17 of 26 [65%] with pacemakers) met criteria for possible hemodynamic benefit and underwent CRT implantation. All 26 patients improved in NYHA functional classification: 5 of 26 patients (19%) were later relisted for HT (4 to 144 months, mean 55 months) after CRT implantation, whereas 21 of 26 (81%) continued with improved NYHA functional class (12 to 112 months, mean 44 months) later. A repeat dP/dt-max study following long-term CRT showed stable function or continued contractility improvement.

CONCLUSIONS

Heart failure is common among CHD patients, and therapies are limited. CRT guidelines do not address clinical and anatomic issues of CHD. Short-term paced contractility response testing identifies those CHD patients who are likely to respond to CRT regardless of anatomy.

The impact of beat-to-beat variability in optimising the acute hemodynamic response in cardiac resynchronisation therapy

BACKGROUND

Acute indicators of response to cardiac resynchronisation therapy (CRT) are critical for developing lead optimisation algorithms and evaluating novel multi-polar, multi-lead and endocardial pacing protocols. Accounting for beat-to-beat variability in measures of acute haemodynamic response (AHR) may help clinicians understand the link between acute measurements of cardiac function and long term clinical outcome.

METHODS AND RESULTS

A retrospective study of invasive pressure tracings from 38 patients receiving an acute pacing and electrophysiological study was performed. 602 pacing protocols for left ventricle (LV) (n = 38), atria-ventricle (AV) (n = 9), ventricle-ventricle (VV) (n = 12) and endocardial (ENDO) (n = 8) optimisation were performed. AHR was measured as the maximal rate of LV pressure development (dP/dtMx) for each beat. The range of the 95% confidence interval (CI) of mean AHR was ~ 7% across all optimisation protocols compared with the reported CRT response cut off value of 10%. A single clear optimal protocol was identifiable in 61%, 22%, 25% and 50% for LV, AV, VV and ENDO optimisation cases, respectively. A level of service (LOS) optimisation that aimed to maximise the expected AHR 5th percentile, minimising variability and maximising AHR, led to distinct optimal protocols from conventional mean AHR optimisation in 34%, 78%, 67% and 12.5% of LV, AV, VV and ENDO optimisation cases, respectively.

CONCLUSION

The beat-to-beat variation in AHR is significant in the context of CRT cut off values. A LOS optimisation offers a novel index to identify the optimal pacing site that accounts for both the mean and variation of the baseline measurement and pacing protocol.