Cardiac resynchronization therapy in patients with a narrow QRS

Long-term performance of modern coronary sinus leads in cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) has become an important pillar of contemporary heart failure therapy. The efficacy of CRT, however, critically relies on proper LV lead placement and performance, which is why data regarding the long-term performance of CS leads are of considerable interest. Available studies are limited by a restricted variety of lead vendors, earlier lead models and / or very short follow-up periods. In the current study, we therefore investigated the long-term performance of modern LV leads in a large "real world" cohort of patients undergoing CRT implantation.

METHODS AND RESULTS

All 193 patients who had successfullyundergone CRT implantation at the University Hospital Zurich between September 2003 and January 2010 were included in the study. An overall stable course of stimulation energy was observed over time; neither ischemic etiology, lead configuration, or severely reduced EF had an influence on the evolution of energy thresholds over time. Interestingly, patients with a high energy threshold at baseline experienced a significant reduction during follow-up. In contrast, a significant drop in impedance was seen following implantation, followed by a steady course for the rest of the observation period. Only 15 patients (9.7%) showed an impedance > 1000 Ohm at any time during their follow-up. Seven lead dislocations were observed during follow up.

CONCLUSION

The current comprehensive analysis of long-term performance of modern coronary sinus leads demonstrates excellent stability, performance and safety. These data may have important implications for physicians involved in biventricular pacemaker implantations and in the follow-up care of these patients.

Determination of the longest intrapatient left ventricular electrical delay may predict acute hemodynamic improvement in patients after cardiac resynchronization therapy

BACKGROUND

One of the reasons for patient nonresponse to cardiac resynchronization therapy is a suboptimal left ventricular (LV) pacing site. LV electric delay (Q-LV interval) has been indicated as a prognostic parameter of cardiac resynchronization therapy response. This study evaluates the LV delay for the optimization of the LV pacing site.

METHODS AND RESULTS

Thirty-two consecutive patients (23 men; mean age, 71±11 years; LV ejection fraction, 30±6%; 18 with ischemic cardiomyopathy; QRS, 181±25 ms; all mean±SD) underwent cardiac resynchronization therapy device implantation. All available tributary veins of the coronary sinus were tested, and the Q-LV interval was measured at each pacing site. The hemodynamic effects of pacing at different sites were evaluated by invasive measurement of LV dP/dtmax at baseline and during pacing. Overall, 2.9±0.8 different veins and 6.4±2.3 pacing sites were tested. In 31 of 32 (96.8%) patients, the highest LV dP/dtmax coincided with the maximum Q-LV interval. Q-LV interval correlated with the increase in LV dP/dtmax in all patients at each site (AR1 ρ=0.98; P<0.001). A Q-LV value >95 ms corresponded to a >10% in LV dP/dtmax. An inverse correlation between paced QRS duration and improvement in LV dP/dtmax was seen in 24 patients (75%).

CONCLUSIONS

Pacing the LV at the latest activated site is highly predictive of the maximum increase in contractility, expressed as LV dP/dtmax. A positive correlation between Q-LV interval and hemodynamic improvement was found in all patients at every pacing site, a value of 95 ms corresponding to an increase in LV dP/dtmax of ≥10%.

The Contemporary Role of Echocardiography in Improving Patient Response to Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) is an important therapy for heart failure patients with widened electrocardiographic QRS complexes and depressed ejection fractions, however, approximately one-third do not respond. This article presents a practical contemporary approach to the utility of echocardiography to improve CRT patient response by assessing mechanical dyssynchrony, optimizing left ventricular lead positioning, and performing appropriate echo-Doppler optimization, along with future potential roles. Specifically, recent long-term outcome data are presented that demonstrates that baseline dyssynchrony is a powerful marker associated with CRT response, in particular for patients with narrower QRS duration or non left bundle branch block morphology. Advances in speckle tracking echocardiography to tailor delivery of CRT by guiding LV lead position is discussed, including data from randomized clinical trials supporting targeting the LV lead toward the site of latest activation. In addition, an update on the current role of Doppler echocardiographic device optimization after CRT implantation is reviewed.

Indications for cardiac resynchronization therapy: 2011 update from the Heart Failure Society of America Guideline Committee

Cardiac resynchronization therapy (CRT) improves survival, symptoms, quality of life, exercise capacity, and cardiac structure and function in patients with New York Heart Association (NYHA) functional class II or ambulatory class IV heart failure (HF) with wide QRS complex. The totality of evidence supports the use of CRT in patients with less severe HF symptoms. CRT is recommended for patients in sinus rhythm with a widened QRS interval (≥150 ms) not due to right bundle branch block (RBBB) who have severe left ventricular (LV) systolic dysfunction and persistent NYHA functional class II-III symptoms despite optimal medical therapy (strength of evidence A). CRT may be considered for several other patient groups for whom evidence of benefit is clinically significant but less substantial, including patients with a QRS interval of ≥120 to <150 ms and severe LV systolic dysfunction who have persistent mild to severe HF despite optimal medical therapy (strength of evidence B), some patients with atrial fibrillation, and some with ambulatory class IV HF. Several evidence gaps remain that need to be addressed, including the ideal threshold for QRS duration, QRS morphology, lead placement, degree of myocardial scarring, and the modality for evaluating dyssynchrony. Recommendations will evolve over time as additional data emerge from completed and ongoing clinical trials.

[Three-dimensional imaging in cardiac resynchronization therapy]

Cardiac resynchronization therapy improves clinical symptoms and prognosis of heart failure patients. However, it has been shown that up to 40% of patients do not respond to this therapy. Three main determinants of cardiac resynchronization therapy response have been identified: left ventricular dyssynchrony, left ventricular lead position, and extent and location of myocardial scar tissue. Two-dimensional echocardiography is the first imaging technique to evaluate patients who may be candidates for cardiac resynchronization therapy. However, a multimodality approach based on 3-dimensional imaging techniques may provide a more comprehensive evaluation of these patients by combining the assessment of the aforementioned pathophysiological determinants of cardiac resynchronization therapy response.

[Cardiac resynchronisation therapy : new data and technical developments]

Cardiac resynchronisation therapy (CRT) has opened up new perspectives over the past 10 years for highly symptomatic patients with severe systolic heart failure. The present article analyses and comments on recent publications which have lead to an expansion of the indication to patients with mild symptoms of heart failure, and which resulted in the modification of current European guidelines in 2010. The data available from narrow QRS complex studies are critically examined. Furthermore, the latest technical innovations in the field of CRT, which have helped to ease the implantation procedure and achieve higher success rates, are presented. Finally, new wireless ultrasound technology to stimulate the left ventricle, currently in an early clinical phase of evaluation, is presented as a potential alternative in the future.

Implantable cardioverter defibrillators and cardiac resynchronisation therapy

Implantable cardioverter defibrillators and cardiac resynchronisation therapy (CRT) have become standard of care in modern treatment for heart failure. Results from trials have provided ample evidence that CRT, in addition to its proven benefits in patients with symptomatic heart failure (New York Heart Association [NYHA] class III), might also reduce morbidity and mortality in those with mildly symptomatic heart failure (NYHA class II). As a result, the 2010 European Society of Cardiology guidelines now recommend CRT for both patient populations. In this review we summarise and critically assess the landmark randomised clinical trials REVERSE, MADIT-CRT, and RAFT. Furthermore, we discuss the rationale and available evidence for other emerging indications of CRT, including its use in patients with a mildly reduced left ventricular ejection fraction (>35%), in those with a narrow QRS complex (≤120 ms), and in those with concomitant bradyarrhythmic pacemaker indications. We also focus on patients who do not respond to CRT, and on CRT optimisation.

[Cardiac resynchronization in narrow QRS and less affected exercise capacity]

Cardiac resynchronization (CRT) through atrio-biventricular pacemaker therapy is now a well established treatment option for severely symptomatic patients with advanced systolic heart failure (HF) and intraventricular conduction delay, especially left bundle branch block. The purpose of this article is to address possible applications of biventricular pacing beyond the classical CRT indication. In particular, a summary is given of available information on CRT in patients with symptomatic systolic HF, but narrow QRS complex, and those with wide QRS, but less pronounced or even absent clinical HF signs.

[Current clinical practise of cardiac resynchronisation therapy in Austria--national results from the European CRT Survey]

Cardiac resynchronization therapy (CRT) has become an established treatment modality in patients with chronic heart failure, reducing both mortality and morbidity. However, patient selection, implantation and follow-up require great clinical experience. Between 2008 and 2010, the European Society of Cardiology initiated the European CRT survey to describe the current practice and routines associated with CRT implantations in 13 countries. Data from 156 patients collected in 10 Austrian centres were analysed compared to the total 2438 patients enrolled. The survey data showed that general practice did not adhere to the present guidelines. More than one third (36%) of the patients had atrial fibrillation and more than one-fourth (29%) had had a device implanted previously. Altogether, 22% of the patients were in NYHA functional class I or II, and 18% had a LVEF > 35%. Approximately one-fourth of the patients were treated with CRT-P devices (Austria 23%, total 27%). In Austria a higher percentage of patients with non-ischemic cardiomyopathy was selected for CRT than in the other European countries (56% versus 40%, p < 0.0001). Less than a quarter of all patients were females. Different from the rest of Europe, only a minority of CRT implantations were performed by cardiologists in Austria (29% as compared to 89% throughout Europe; p < 0.0001).

Heart failure patients selection for cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is an established treatment for refractory chronic heart failure (CHF) patients with ventricular dyssynchrony. The patient selection for this therapy remains the basis for response improvement. Various parameters, methods and technology for identification of appropriate patient are under research. The influences of age and gender, disease progress stage such as mild and late stage CHF including right ventricular dysfunction, dyssynchrony and scar identified by imaging techniques like echocardiography, magnetic resonance and nuclear imaging, and atrial fibrillation on CRT benefits were respectively discussed. This review summarizes the current advancement in these areas.

Cardiac resynchronization therapy guided by cardiovascular magnetic resonance

Cardiac resynchronization therapy (CRT) is an established treatment for patients with symptomatic heart failure, severely impaired left ventricular (LV) systolic dysfunction and a wide (> 120 ms) complex. As with any other treatment, the response to CRT is variable. The degree of pre-implant mechanical dyssynchrony, scar burden and scar localization to the vicinity of the LV pacing stimulus are known to influence response and outcome. In addition to its recognized role in the assessment of LV structure and function as well as myocardial scar, cardiovascular magnetic resonance (CMR) can be used to quantify global and regional LV dyssynchrony. This review focuses on the role of CMR in the assessment of patients undergoing CRT, with emphasis on risk stratification and LV lead deployment.

Association of intraventricular mechanical dyssynchrony with response to cardiac resynchronization therapy in heart failure patients with a narrow QRS complex

AIMS

current criteria for cardiac resynchronization therapy (CRT) are restricted to patients with a wide QRS complex (>120 ms). Overall, only 30% of heart failure patients demonstrate a wide QRS complex, leaving the majority of heart failure patients without this treatment option. However, patients with a narrow QRS complex exhibit left ventricular (LV) mechanical dyssynchrony, as assessed with echocardiography. To further elucidate the possible beneficial effect of CRT in heart failure patients with a narrow QRS complex, this two-centre, non-randomized observational study focused on different echocardiographic parameters of LV mechanical dyssynchrony reflecting atrioventricular, interventricular and intraventricular dyssynchrony, and the response to CRT in these patients.

METHODS AND RESULTS

a total of 123 consecutive heart failure patients with a narrow QRS complex (<120 ms) undergoing CRT was included at two centres. Several widely accepted measures of mechanical dyssynchrony were evaluated: LV filling ratio (LVFT/RR), LV pre-ejection time (LPEI), interventricular mechanical dyssynchrony (IVMD), opposing wall delay (OWD), and anteroseptal posterior wall delay with speckle tracking (ASPWD). Response to CRT was defined as a reduction ≥15% in left ventricular end-systolic volume at 6 months follow-up. Measures of dyssynchrony can frequently be observed in patients with a narrow QRS complex. Nonetheless, for LVFT/RR, LPEI, and IVMD, presence of predefined significant dyssynchrony is <20%. Significant intraventricular dyssynchrony is more widely observed in these patients. With receiver operator characteristic curve analyses, both OWD and ASPWD demonstrated usefulness in predicting response to CRT in narrow QRS patients with a cut-off value of 75 and 107 ms, respectively.

CONCLUSION

mechanical dyssynchrony can be widely observed in heart failure patients with a narrow QRS complex. In particular, intraventricular measures of mechanical dyssynchrony may be useful in predicting LV reverse remodelling at 6 months follow-up in heart failure patients with a narrow QRS complex, but with more stringent cut-off values than currently used in 'wide' QRS patients.

Upgrading to resynchronization therapy after chronic right ventricular pacing improves left ventricular remodelling

AIMS

Chronic right ventricular (RV) pacing may impose ventricular dyssynchrony leading to LV remodelling and is associated with increased morbidity and mortality. Upgrading patients with chronic RV pacing to cardiac resynchronization therapy (CRT) may be considered to restore synchronicity and prevent these deleterious effects.

METHODS AND RESULTS

A total of 172 patients from two tertiary centres were analysed over a mean follow-up of 21.7 and 23.5 months after primary CRT implantation (n = 102) and CRT upgrade (n = 70), respectively. In the latter group, mean duration of RV pacing before CRT upgrade was 80.3 months, and ventricular stimulation was >95%. A significant improvement in left ventricular (LV) ejection fraction (10 and 11% absolute increase in primary CRT vs. upgrades, respectively), LV end-diastolic diameter index (-0.15 cm/m(2) vs. -0.2 cm/m(2)), and LV end-systolic diameter (-6.0 vs. -7.0 mm) was observed in both groups, which did not differ between primary CRT recipients and CRT upgrades. Response to CRT upgrade was independent of the underlying rhythm, QRS duration, duration of prior RV pacing, or LV function and size at baseline. Of note, even seven of nine patients with RV pacing >12 years responded favourably to CRT.

CONCLUSION

The current study demonstrates that CRT reverses LV remodelling in heart failure patients with chronic RV pacing in a similar way as in primary CRT recipients, even after very long periods of RV pacing. Our data, therefore, may have important implications for the treatment of pacemaker-dependent patients with heart failure, and support the use of CRT in this setting.