Effects of Stimulation Site on Diastolic Function in Cardiac Resynchronization Therapy

Background : Cardiac resynchronization therapy (CRT) improves left ventricular (LV) systolic function and clinical status, and prolongs survival of patients suffering from heart failure. An optimal LV site selection is key with respect to improvements in systolic function, though whether a site-specific effect on diastolic function exists is unclear. This study compared the effects of CRT on changes in systolic and diastolic function from 2 LV stimulation sites.
Methods : We studied 21 patients in New York Heart Association functional classes ≥III, and a LV ejection fraction <0.30 and QRS duration > 130 ms. CRT leads were placed in the right ventricle, right atrium, and coronary sinus tributaries. LV stimulation was applied from the postero-lateral and antero-lateral wall. A LV conductance catheter was used to measure LV systolic and diastolic function. Systolic responders had >10% changes in dP/dt_max, and diastolic responders <10% changes in τ during CRT versus baseline. Response was highly dependent on LV lead position for both diastolic and systolic function. Diastolic responders decreased from 29% to 10% of patients, and systolic responders from 76% to 48%, in the best versus the worst lead position, respectively. Improvements in diastolic function were less pronounced than in systolic function (relative change −14% vs +28%, P < 0.05). Overall, 45% were both systolic and diastolic responders, 17% were both systolic and diastolic nonresponders, and 38% had opposite responses .
Conclusions : Changes in systolic and diastolic function were both highly dependent on the LV stimulation site. Diastolic function was less influenced by CRT and a high proportion of patients had discordant results.     

Segmental Wall Motion Abnormality Analyzed by Equilibrium Radionuclide Angiography and Improvement in Ventricular Function by Cardiac Resynchronization Therapy

Introduction: The purpose of this study was to determine the impact of the left ventricular (LV) segmental wall motion abnormalities detected by equilibrium radionuclide angiography (ERNA) on the improvement in LV and right ventricular (RV) function during biventricular (BIV) stimulation .
Results: We studied 28 patients in NYHA functional classes III or IV and QRS duration >150 ms on resting electrocardiogram. ERNA was performed before and during BIV stimulation at a 6-month follow-up. A significant shortening of QRS duration was observed during BIV stimulation (165 ± 5 ms before vs 133 ± 6 ms during, P < 0.01). Wall motion abnormalities (WMA) were observed in 16 patients (10 with nonischemic cardiomyopathies). In this group, LV and RV ejection fractions (EF) did not increase during BIV stimulation (LVEF = 22 ± 2% vs 20 ± 1.6%, ns; RVEF = 34 ± 3% vs 37 ± 3.8%, ns). Significant increases in RVEF (23 ± 3.2 %→ 38 ± 2.9%, P = 0.001) and LVEF (20 ± 2.5 %→ 30 ± 3%, P = 0.01) were observed in the group of patients without segmental WMA and with global hypokinesia (GH). In this group, a significant decrease in the dispersion in the phase of RV contraction was observed (SD = 39 ± 5 vs 26 ± 2 ms; P < 0.01). WMA predicted an increase in LVEF, in contrast to a baseline 6-minute-walk test, maximal oxygen consumption and LVEF, or amount of QRS shortening.
Conclusions: BIV stimulation increased in LV and RV EF in patients with ventricular dyssynchrony in absence of segmental WMA. ERNA was reliable in the selection of candidates for CRT.     

Cardiac Resynchronization Therapy in Pediatric and Congenital Heart Disease

Cardiac resynchronization therapy (CRT) is an emerging option for treating dyssynchrony-associated heart failure in patients with pediatric or congenital heart disease. CRT has proved beneficial for both the acute manipulation of cardiac output after surgery for congenital heart defects and for the management of chronic systemic ventricular failure. Although there are no prospective and randomized trial data, retrospective series show that CRT is similarly effective for managing dyssynchrony-associated heart failure in this younger population as it is for treating adults with ischemic and idiopathic dilated cardiomyopathy. The heterogeneity of anatomical and functional substrates in which CRT shows efficacy calls for further studies defining the usefulness of CRT in specific subgroups of patients.     

Proportion of Candidates for Cardiac Resynchronization Therapy

ERDOGAN, A., et al. : Proportion of Candidates for Cardiac Resynchronization Therapy. Biventricular pacing has been used as an adjunct to standard heart failure therapy in symptomatic patients with left bundle branch block (LBBB). Estimates of the number of patients for whom this treatment is appropriate are unavailable, but are of clinical and socioeconomic importance. LBBB combined with a low (<0.35) ejection fraction was found in 7,121 consecutive patients referred for elective diagnostic angiography in 1996 through 2000 from a total population of about 125,000 residents. Patients with LBBB (n = 289, 4%) had lower ejection fractions (0.53 ± 0.23) in comparison with patients without LBBB (P < 0.0001). The ejection fraction was <0.35 in 558 (8%) patients. LBBB was combined with a low ejection fraction in 96 (1.4%) patients (i.e., 19 patients per year and about 15 patients per year per 100,000 residents). Of these 96 patients, 80 had normal sinus rhythm, 82 had mitral regurgitation (grade > II), 86 were <75 years of age, and 68 had coronary artery disease. Holter recordings performed in 47 of 96 patients showed nonsustained VT in 28 (60%). LBBB, low ejection fraction, sinus rhythm, and age <75 years were found in 71 (1%) patients (i.e., 11 patients per year per 100,000 residents). The prevalence of LBBB combined with severely impaired left ventricular ejection function is about 1–2% in patients who undergo cardiac catheterization. The authors estimate that biventricular pacing might be considered as an adjunct to standard heart failure therapy in five to ten patients per year per 100,000 residents in industrial countries. About half of these patients are potential candidates for implantation of cardioverter defibrillators combined with permanent pacing. (PACE 2003; 26[Pt. II]:152–154)     

Cardiac Resynchronization Therapy:

In patients with heart failure and wide QRS complex, cardiac resynchronization therapy (CRT) is associated with improvement of symptoms and cardiac function. This study examined the effects of a 3-month period of CRT on left ventricular (LV) and right ventricular (RV) ejection fraction (EF) and on LV volumes, both at rest and during exercise. A CRT system was implanted in 15 patients with severe heart failure and wide QRS. Before implant and 3 months later, all patients underwent assessment of cardiac performance with equilibrium Tc⁹⁹ radionuclide angiography with imaging in the best septal left anterior oblique view. Exercise was performed on a bicycle ergometer. At 3 months, a significant improvement in New York Heart Association functional class was observed, and radionuclide angiography showed a significant decrease in LV volumes and a significant increase in LVEF at rest, as well as a significant increase in LVEF during exercise. The remodeling processes associated with CRT did not appear to include RV function, since RVEF did not improve, and changes in RVEF did not correlate with changes in LVEF, neither at rest nor during exercise.     

Influence of Different Atrioventricular and Interventricular Delays on Cardiac Output During Cardiac Resynchronization Therapy

Restoration of the atrioventricular (AVD) and interventricular (VVD) delays increases the hemodynamic benefit conferred by biventricular (BiV) stimulation. This study compared the effects of different AVD and VVD on cardiac output (CO) during three stimulation modes: BiV-LV = left ventricle (LV) preceding right ventricle (RV) by 4 ms; BiV-RV = RV preceding LV by 4 ms; LVP = single-site LV pacing. We studied 19 patients with chronic heart failure due to ischemic or idiopathic dilated cardiomyopathy, QRS ≥ 150 ms, mean LV end-diastolic diameter = 78 ± 7 mm, and mean LV ejection fraction = 21 ± 3%. CO was estimated by Doppler echocardiographic velocity time integral formula with sample volume placed in the LV outflow tract. Sets of sensed-AVDs (S-AVD) 90–160 ms, paced-AVDs (P-AVD) 120–160 ms, and VVDs 4–20 ms were used. BiV-RV resulted in lower CO than BiV-LV. S-AVD 120 ms and P-AVD 140 ms caused the most significant increase in CO for all three pacing modes. LVP produced a similar increase in CO as BiV stimulation; however, AV sequential pacing was associated with a nonsignificantly higher CO during LVP than with BiV stimulation. CO during BiV stimulation was the highest when LV preceded RV, and VVD ranged between 4 and 12 ms. The most negative effect on CO was observed when RV preceded LV by 4 ms. Hemodynamic improvement during BiV stimulation was dependent both on optimized AVD and VVD. LV preceding RV by 4–12 ms was the most optimal. Advancement of the RV was not beneficial in the majority of patients.     

Is the Left Ventricular Lateral Wall the Best Lead Implantation Site for Cardiac Resynchronization Therapy?

GASPARINI, M., et al .: Is the Left Ventricular Lateral Wall the Best Lead Implantation Site for Cardiac Resynchronization Therapy? Short-term hemodynamic studies consistently report greater effects of cardiac resynchronization therapy (CRT) in patients stimulated from a LV lateral coronary sinus tributary (CST) compared to a septal site. The aim of the study was to compare the long-term efficacy of CRT when performed from different LV stimulation sites. From October 1999 to April 2002, 158 patients (mean age 65 years, mean LVEF 0.29, mean QRS width 174 ms) underwent successful CRT, from the anterior (A) CST in 21 patients, the anterolateral (AL) CST in 37 patients, the lateral (L) CST in 57 patients, the posterolateral (PL) CST in 40 patients, and the middle cardiac vein (MCV) CST in 3 patients. NYHA functional class, 6-minute walk test, and echocardiographic measurements were examined at baseline, and at 3, 6, and 12 months. Comparisons were made among all pacing sites or between lateral and septal sites by grouping AL + L + PL CST as lateral site (134 patients, 85%) and A + MC CST as septal site (24 patients, 15%). In patients stimulated from lateral sites, LVEF increased from 0.30 to 0.39   (P < 0.0001)   , 6-minute walk test from 323 to 458 m   (P < 0.0001)   , and the proportion of NYHA Class III–IV patients decreased from 82% to 10%   (P < 0.0001)   . In patients stimulated from septal sites, LVEF increased from 0.28 to 0.41   (P < 0.0001)   , 6-minute walk test from 314 to 494 m   (P < 0.0001)   , and the proportion of NYHA Class III–IV patients decreased from 75% to 23%   (P < 0.0001)   . A significant improvement in cardiac function and increase in exercise capacity were observed over time regardless of the LV stimulation sites, either considered singly or grouped as lateral versus septal sites. (PACE 2003; 26[Pt. II]:162–168)     

Effects of Cardiac Resynchronization Therapy on Heart Rate Turbulence

Background: Cardiac resynchronization therapy (CRT) improves the clinical status of patients with heart failure (HF), though its effects on heart rate turbulence (HRT) are unknown.
Methods: We measured HRT indices in 58 recipients of CRT systems (mean age = 56 ± 9 years, 41 men) in New York Heart Association HF functional class III–IV, and with a left ventricular (LV) ejection fraction ≤35%. At 6 months of follow-up, 42 patients were responders and 13 nonresponders to CRT, and three patients died suddenly. The HRT indices turbulence onset (TO%) and turbulence slope (TS ms/RR interval) were calculated from digital 24-hour electrocardiogram before and after 6 months of CRT. TO ≥ 0% and TS ≤ 2.5 ms/RR interval were considered abnormal.
Results: Mean TO in the entire population was 0.4 ± 1.5 before CRT, and decreased to −0.8 ± 7.0 during the 6 months of CRT (ns). TS increased significantly from 2.0 ± 1.7 at baseline, to 3.9 ± 3.1 (P < 0.05), and a significantly lower proportion of patients had abnormal HRT indices at 6 months. In contrast to the significant increase observed in responders, not significant change in TS was observed among the nonresponders.
Conclusions: During 6 months of CRT, improvements in HRT indices and a decrease in the proportion of patients with abnormal HRT were observed. CRT may have beneficial effects on baroreflex sensitivity.     

Long-Term Variations in Optimal Programming of Cardiac Resynchronization Therapy Devices

The optimal follow-up and long-term programming of cardiac resynchronization therapy (CRT) devices are uncertain. The aim of this study was to quantify the temporal variations in programming parameters to optimize the follow-up of these devices. Before, during, and at specified intervals over 9 months after implant, 40 recipients of CRT devices were studied. At each visit, the patients were tested with a fixed sequence of stimulation parameters during echocardiographic and electrocardiographic (ECG) recordings. The optimal AV delay and inter-ventricular delays (V-V) were determined according to echocardiographic criteria. The echocardiographic data were, in turn, compared with the ECG recordings. Among the 40 patients, the optimal stimulation parameters remained unchanged throughout the follow-up in only three patients. In 18 patients, adjustments were required at each follow-up sessions. There was a trend toward reduction in the left ventricular (LV) predominance of the optimal V-V delay and an increase in the AV delay during follow-up. The mean optimal V-V delay at implant was 22 ms (−12 to +32 ms) with the LV activated first, versus 12 ms (−16 to +32 ms) at 9 months. The mean AV delay at implant was 115 ms versus 137 ms at 9 months. Individual changes could not be accurately predicted. The optimal stimulation parameters for CRT vary over time. Detailed, regular reevaluations, and reprogramming of optimal parameters may be appropriate.     

Advantage of Optimizing V‐V Timing in Cardiac Resynchronization Therapy Devices

Background: There is little consensus as to the benefits of interventricular (V‐V) timing optimization in cardiac resynchronization therapy (CRT). A variety of parameters are currently used to optimize device timing. This study was designed to investigate the potential advantage of using 3D ejection fraction (EF) and aortic velocity‐time integral (VTI) as measures of global left ventricular (LV) function to optimize ventricular activation in CRT devices. Methods: Seventy‐four patients seen in the Optimization Clinic with adequate echocardiographic images were included. Three aortic VTI and two 3D EF values were recorded at five V‐V settings and the average value used. Aortic VTI and 3D EF were classified as the best, worst, and simultaneous setting values. Data were analyzed using a two‐tailed paired t‐test. Results: Comparing the best to worst V‐V timing settings, VTI improved by 4.7 ± 7.5 cm (P < 0.0001) and 3D EF by 9.9%± 5.7% (P < 0.0001). Comparing the simultaneous setting to the best V‐V timing setting, VTI improved by 2.4 ± 2.1 cm (P < 0.0001) and 3D EF by 3.8%± 4.9% (P < 0.0001). Aortic VTI improved in 85% of patients and 3D EF improved in 72%. However, only 26% of the patients had the same optimal setting using aortic VTI and 3D EF yielding an r² value of 0.003. Conclusions: Individualized echocardiographic V‐V optimization of CRT devices improves global LV function as measured by aortic VTI and 3D EF. Substantial differences in function were seen over an 80‐ms range of V‐V timing and optimization resulted in improved LV function in the majority of patients. (PACE 2010; 33:1161–1168)     

Utilization of Defibrillators and Resynchronization Therapy at the Time of Evaluation at a Heart Failure and Cardiac Transplantation Center

Background: Internal cardioverter defibrillators (ICDs) and cardiac resynchronization therapy (CRT) reduce mortality, but are underutilized in routine clinical practice. The use of these devices in patients at the time of an initial evaluation at an advanced heart failure and cardiac transplantation center is unknown. Methods: We retrospectively analyzed consecutive patients who were enrolled in a database examining parameters of cardiopulmonary exercise testing in chronic heart failure (CHF) patients at the time of an initial outpatient evaluation at a tertiary care center. Rates of ICD and CRT use in eligible patients were determined. Results: Two hundred two patients had an average age of 54 ± 13 years and an average peak oxygen consumption (pVO₂) of 12.5 ± 4.5 mL/kg/min. Of 97 patients eligible for an ICD only, 57% had an ICD at the time of evaluation. Sixty‐four percent of ICD‐eligible male patients had an ICD compared to 36% of ICD‐eligible female patients (P = 0.015). Of 105 patients meeting criteria for CRT, 54% had a CRT device. There was no difference between CRT use in eligible male and female patients. Conclusions: ICDs and CRT are underutilized in patients with severe CHF at the time of evaluation at a tertiary care center despite young age, objective functional limitation, and active consideration for advanced CHF therapies. Female patients have lower rates of ICD use than male patients. (PACE 2010; 988–993)     

Cardiac Resynchronization Therapy in Patients with Right Ventricular Pacing-Induced Cardiomyopathy

Background: It is not known whether patients with normal baseline left ventricular (LV) function who develop right ventricular (RV) pacing-induced cardiomyopathy as a result of dual-chamber pacing can benefit from cardiac resynchronization therapy (CRT). We retrospectively assessed the effect of a CRT upgrade on RV pacing-induced cardiomyopathy.
Methods and Results: We reviewed the charts of patients who received a CRT device for RV pacing-induced cardiomyopathy. We assessed the effects of CRT on LV function, recovery, and other response parameters. From September 2005 through February 2009, 21 patients (13 men; aged 63 ± 9 years) underwent a treatment upgrade to a CRT system. Before the dual-chamber pacemaker was implanted, the LV ejection fraction (LVEF) was 53 ± 2.3%. After pacing, the LVEF was 31.2 ± 3.8%, the LV end-diastolic dimension (LVEDD) was 5.8 ± 0.5 cm, and B-type natriuretic peptide (BNP) levels were 426 ± 149 pg/mL. The duration of pacing before documentation of pacing-induced cardiomyopathy was 3.8 ± 1.5 months. All the patients had been on a stable medical regimen for at least 2 months. After the upgrade to CRT, the follow-up time was 4.9 ± 0.9 months. Sixteen patients (76%) reported a significant improvement in their symptoms. After the CRT upgrade, the LVEF increased to 37.4 ± 9.0% (P < 0.01 vs pre-CRT). The LVEDD decreased to 5.0 ± 1.0 cm (P = 0.03 vs pre-CRT), and BNP levels decreased to 139 ± 92 pg/mL (P = 0.08 vs pre-CRT).
Conclusion: A CRT upgrade is an effective treatment for RV pacing-induced cardiomyopathy and should be implemented as soon as the diagnosis is established. Unfortunately, about 24% of our patients did not respond to the upgrade. (PACE 2010; 37–40)     

Long-Term Effectiveness of Dual Site Left Ventricular Cardiac Resynchronization Therapy in a Patient with Congestive Heart Failure

This article describes a case of cardiac resynchronization therapy (CRT) performed with dual site left ventricular pacing. The main clinical and functional long-term results are in agreement with the most recent data regarding traditional CRT. Furthermore, this innovative pacing modality allowed optimal inter- and intraventricular resynchronization. (PACE 2004; 27[Pt. I]:805–807)