Highlighting the R in CRT

Cardiac resynchronization therapy outcomes in patients under nonoptimal medical therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) is indicated in symptomatic heart failure (HF) patients after achieving optimal medical therapy (OMT). However, many patients may not be under OMT when the CRT device is implanted. Here, we evaluate the long-term benefits of CRT in symptomatic HF patients receiving or not OMT.

METHODS

We investigated the effect of OMT on HF developing or death in 328 consecutive patients with a CRT device implanted between 2005 and 2015 in a single tertiary center. After the CRT implant, we categorized the patients into three groups: no OMT, OMT at baseline and after 1 year of follow-up, and OMT only at the 1-year follow-up but not at baseline. We used multivariate Cox proportional hazards model to determine the effect of OMT on clinical outcomes.

RESULTS

One hundred and twenty-two patients (37.2%) received OMT prior to CRT. OMT at baseline was not associated with a reduced risk of death or HF (HR 0.72; 95% CI 0.50-1.02; P = 0.067) compared with no-basal-OMT patients. After CRT, patients without OMT had a higher risk of death or HF than patients who received OMT in follow-up (HR 1.72, 95% CI 1.07-2.78, P = 0.025), and the risk of the patients who received OMT at baseline and at the 1-year follow-up was similar to that of the patients who achieved OMT at the 1-year follow-up (HR 0.90, 95% CI 0.54-1.50, P = 0.682).

CONCLUSION

Basal OMT prior to CRT is not associated with better outcomes in terms of HF/death compared with no basal OMT. The subgroup of patients who achieved OMT at the 1-year follow-up exhibited a reduced risk of HF and death compared with patients who did not.

Importance of adjunctive heart failure optimization immediately after implantation to improve long-term outcomes with cardiac resynchronization therapy

Despite improvement in morbidity and mortality with cardiac resynchronization therapy (CRT), disease progression continues to affect a subset of patients and there is limited effort to identify contributing factors. Our objective was to investigate if a protocol-driven approach incorporated in a management strategy of heart failure immediately after implantation would provide incremental benefits beyond usual care after implantation. We reviewed 114 consecutive patients with CRT implanted from 2005 through 2009 who received usual care after implantation or underwent protocol-driven CRT care after implantation. Preimplantation characteristics in patients receiving usual versus protocol-driven care were similar in left ventricular (LV) dimension (LV internal diastolic diameter 6.2 ± 0.8 vs 6.4 ± 1.0 cm), LV ejection fraction (26 ± 8% vs 25% ± 8%), QRS width, and medication usage. Major adjustments during the protocol-driven approach were uptitration of neurohormonal blockers (64%), echocardiographically guided atrioventricular optimization (50%), heart failure education (42%), arrhythmia management (19%), and LV lead repositioning (7%). Although positive LV remodeling was noted in the 2 groups at 6 months, extent was significantly greater in the protocol-driven approach compared to usual care (change in LV internal diastolic diameter 0.7 ± 0.6 cm vs 0.2 ± 1.2 cm, p = 0.01; change in LV ejection fraction 11 ± 7% vs 7 ± 9%, p = 0.01), which was associated with fewer major adverse events (14% vs 53%, p <0.001). In conclusion, a protocol-driven approach for patients with CRT started immediately after implantation is associated with incremental favorable effects on reverse remodeling and fewer adverse events compared to usual care after implantation. These effects appeared to be driven not only by changes in device settings and arrhythmia management but also by concomitant medication optimization and heart failure education.

A prospective pilot study to evaluate the relationship between acute change in left ventricular synchrony after cardiac resynchronization therapy and patient outcome using a single-injection gated SPECT protocol

BACKGROUND

There are ongoing efforts to optimize patient selection criteria for cardiac resynchronization therapy (CRT). In this regard, the relationship between acute change in left ventricular synchrony (LV) after CRT and patient outcome remains undefined.

METHODS AND RESULTS

A novel protocol was designed to evaluate acute change in left LV synchrony after CRT using phase analysis of standard gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging with a single injection of radiotracer and prospectively applied to 44 patients undergoing CRT. Immediately after CRT, 18 (41%), 11 (25%), and 15 (34%) patients had an improvement, no change, or a worsening in LV synchrony. An algorithm incorporating the presence of baseline dyssynchrony, myocardial scar burden, and lead concordance predicted acute improvement or no change in LV synchrony with 72% sensitivity, 93% specificity, 96% positive predictive value, and 64% negative predictive value and had 96% negative predictive value for acute deterioration in synchrony. Over a follow-up period of 9.6 ± 6.8 months, patients who had an acute deterioration in synchrony after CRT had a higher composite event rate of death, heart failure hospitalizations, appropriate defibrillator discharges, and CRT device deactivation for worsening heart failure symptoms, compared with patients who had an improvement or no change [hazard ratio, 4.6 (1.3 to 16.0); log rank test; P=0.003].

CONCLUSIONS

In this single-center pilot study, phase analysis of gated SPECT was successfully used to predict acute change in LV synchrony and patient outcome after CRT.

Pathobiology of cardiac dyssynchrony and resynchronization

Cardiac resynchronization therapy (CRT) represents the major new advance for treatment of heart failure since the start of the new millennium. With this therapy, failing hearts with discoordinate contraction due to conduction delay are subjected to biventricular stimulation to "resynchronize" contraction and improve chamber function. Remarkably, CRT was mostly developed and tested in patients first, and the speed at which the concept was translated to an approved clinical therapy was unusually quick. To date, CRT is the only heart failure treatment that can both acutely and chronically improve the systolic pump performance of the failing human heart yet also enhance long-term survival. This situation underscores the importance of understanding how CRT works at the molecular and cellular levels, as these insights might shed light on new approaches to treating heart failure more generally. Over the past 7 years, my laboratory and others at Johns Hopkins have developed novel animal models for addressing this question, and new results are revealing intriguing insights into the mechanisms of CRT. This review, presented on the occasion of the Fourth Annual Douglas P. Zipes Lecture at the 2009 Scientific Sessions of the Heart Rhythm Society, highlights these advances and new directions in CRT research.