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)     

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)     

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.     

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.     

Effects of Cardiac Resynchronization Therapy on Diastolic Function: Evaluation by Radionuclide Angiography

While the beneficial effects of cardiac resynchronization therapy (CRT) on left ventricular (LV) systolic function have been demonstrated, no information is available regarding its effects on LV diastolic function during exercise. Using radionuclide angiography, we prospectively evaluated the effects of CRT on diastolic function at rest and during exercise in 15 patients consecutively referred for CRT. All patients underwent equilibrium Tc⁹⁹ radionuclide angiography with bicycle exercise performed (1) at baseline; (2) immediately after CRT implantation, in spontaneous rhythm and during CRT; and (3) after 3 months of biventricular stimulation. Diastolic function was assessed by measurements of peak filling rate (PFR). At baseline, activation of biventricular stimulation influenced PFR neither at rest (1.06 ± 0.34 vs 1.07 ± 0.50 mL/s during spontaneous rhythm, P = 0.9) nor during exercise (1.45 ± 0.62 vs 1.33 ± 0.48 mL/s, P = 0.3). At 3 months, improvements were observed in New York Heart Association functional class and systolic function. By contrast, no improvement in diastolic function was observed either at rest (PFR = 1.11 ± 0.45 vs 1.07 ± 0.50 mL/s in spontaneous rhythm at baseline, P = 0.6) or during exercise (1.23 ± 0.50 vs 1.33 ± 0.48 mL/s, P = 0.2). These observations indicate that the intermediate benefits conferred by CRT on LV systolic function at rest and during exercise were not accompanied by similar improvements in diastolic function .     

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.     

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)     

Technical Aspects of Implantation of LV Lead for Cardiac Resynchronization Therapy in Chronic Heart Failure

The goal of this study was to analyze total procedural and fluoroscopic time during initial experience with implantation of LV lead in a single center, and to assess the performance of electrophysiologically-guided approach for cannulation of the coronary sinus (CS) in a subsequent period. Over an initial period of 29 months, a total of 46 attempts to implant biventricular pacing system were revised. During the first phase, only one type of LV electrode was available for three implanters (11 attempts). The second phase covered their early experience with other stylet-controlled LV leads (10 attempts). Additional LV leads including the over-the-wire design were available in the third phase and 25 attempts were done by he most experienced implanter. In a period of advanced experience, 92 implant procedures performed by four implanters using an electrophysiologically-guided approach to CS cannulation were revised. In the first period, success rates for different phases reached 70%, 90%, and 96%, respectively. Significant decrease in both procedural and fluoroscopic times was achieved with increased experience (Phase I: 247.1 ± 104.5 minutes and 31.2 ± 34.3 minutes, Phase II: 219.4 ± 85.6 minutes, and 22.9 ± 19.1 minutes, Phase III: 116.4 ± 89.9 minutes and 6.6 ± 4.4 minutes, respectively, P < 0.05). Advanced experience with electrophysiologically-guided approach to CS cannulation allowed achievement of this target within a reasonable amount of time (15.4 ± 16.3 minutes) and with minimum fluoroscopic time (2.1 ± 2.9 minutes). In conclusion, both individual learning curve and technical advances significantly influence success rate, procedural, and fluoroscopic times for biventricular system implantation. Electrophysiologically-guided approach makes cannulation of the CS a highly reproducible procedure that requires minimum fluoroscopic time. (PACE 2004; 27[Pt. I]:783–790)     

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)     

Long-Term Follow-Up of Patients with Refractory Heart Failure and Myocardial Ischemia Treated with Cardiac Resynchronization Therapy

Studies in patients without coronary artery disease have shown the restoration of glucose metabolism by cardiac resynchronization therapy (CRT) without changes in myocardial perfusion. We report on the long-term outcome of CRT in 24 patients with severe heart failure (HF) and advanced coronary artery disease not amenable for revascularization. All patients had documented myocardial ischemia on stress ⁹⁹Tc-sestamibi single-photon emission computed tomography, and all underwent successful implantations of CRT systems. The mean left ventricular ejection fraction was 21%± 4%, 19 patients (79%) had anginal complaints and 20 (83%) had diffuse three-vessel disease. During a follow-up of 13 ± 0.7 months, two patients died suddenly and one died of progressive HF. Among survivors, functional capacity decreased from New York Heart Association class 3.2 ± 1.4 to 2.1 ± 1.0 (P < 0.01), and the Minnesota questionnaire quality-of-life scores decreased from 43 ± 15 to 28 ± 13 (P < 0.01). Despite an increase from 264 ± 104 to 385 ± 121 m in distance walked in 6 minutes (P < 0.01), the number of anginal attacks/week remained unchanged (4.7 ± 0.7 to 4.5 ± 0.6). Patients with advanced HF, stable angina, and documented myocardial ischemia may undergo safe and successful implantations of CRT systems.     

曲美他嗪对冠心病慢性心力衰竭患者心功能及心率震荡的影响

目的观察曲美他嗪对冠心病慢性心力衰竭患者心功能及窦性心率震荡(HRT)的影响。方法2009 年10 月~2012 年6月经冠脉造影和/或CT血管造影(CTA)证实的73 例冠心病慢性心力衰竭患者,随机分成对照组(n=35)和曲美他嗪组(n=38)。对照组采用常规强心、利尿、扩血管等抗心力衰竭治疗;曲美他嗪组在此基础上给予口服曲美他嗪片。两组分别于服药前和服药3 个月后检查心脏彩色多普勒超声心动图、24 h 动态心电图,测算左心室射血分数(LVEF)、左室舒张末期内径(LVd)以及反映HRT的两个量化指标震荡初始(TO)和震荡斜率(TS)。结果经3 个月治疗,两组LVEF提高,LVd缩小(P<0.01)。曲美他嗪组LVEF改善显著优于对照组(P<0.001)。曲美他嗪组TO和TS均改善(P<0.05),对照组仅TO改善(P<0.05)。曲美他嗪组TO和TS改善均优于对照组(P<0.05)。结论曲美他嗪有助于改善冠心病慢性心力衰竭患者的心功能,改善HRT现象。     

窦性心率震荡评估冠心病病人预后的价值研究

目的观察冠心病（CHD）病人窦性心率震荡（HRT）的特征,明确其对CHD病人发生心脏不良事件的预测价值。方法选择年龄、性别相匹配的CHD病人（CHD组）和健康体检者（对照组）各60例,均进行24 h心电图（Holter）检查,对2组HRT的2个指标：震荡初始（TO）和震荡斜率（TS）进行比较。并对CHD病人进行6-12个月跟综随访,了解心脏不良事件（心肌再梗死、再发心绞痛、恶性心律失常、心脏猝死）的发生情况。结果与对照组比较,CHD组TO增高,为（1.08±0.27）%vs（0.18±0.33）%,TS减小,为（3.12±0.87）ms·RRI^-1vs（6.51±0.63）ms·RRI^-1（均P〈0.05）;CHD组中不良事件组TO高于非不良事件组,TS低于非不良事件组（均P〈0.05）。结论CHD病人HRT减弱,而发生心脏不良事件的病人HRT减弱更严重。HRT可作为CHD病人预后的一个评估指标。     

Adrenomedullin Plasma Levels Predict Left Ventricular Reverse Remodeling after Cardiac Resynchronization Therapy

Background: Increase in adrenomedullin (ADM) plasma levels in congestive heart failure (HF) patients is due to many cardiac and systemic factors, particularly to greater fluid retention and to activation of sympathetic nervous system. Aim of this study was to assess the role of plasma ADM levels in HF patients treated by cardiac resynchronization therapy (CRT). Methods: 50 patients, mean age 70 years, 34 male, New York Heart Association (NYHA) Class III–IV HF, left ventricular ejection fraction (LVEF) < 35%, underwent CRT. All patients were in sinus rhythm and with complete left bundle branch block (QRS duration 138 ± 6 msec). A complete echoDoppler exam, blood samples for brain natriuretic peptide (BNP), and ADM were obtained from 2 to 7 days before implantation. Results: At 16 ± 6 months follow‐up, ≥1 NYHA Class improvement was observed in 38 patients. However, a >10% reduction in end‐systolic dimensions (ESD) was reported in 21 patients (Group I): ?16.6 ± 1.8%; in the remaining 29 patients ESD change was almost negligible: ?2.0 ± 1.03% (Group II), P < 0.0001. The two groups were comparable for age, sex, cause of LV dysfunction, therapy, QRS duration at baseline, preimplantation ESD, LVEF%, and BNP. Significantly higher pre implantation ADM levels were present in Group I than in Group II (27.2 ± 1.8 pmol/l vs 17.9 ± 1.4, P = 0.0003). Conclusions: Significantly higher ADM levels indicate a subgroup of patients in whom reverse remodeling can be observed after CRT. Patients with lower ADM basal values before CRT could represent a group in whom the dysfunction is so advanced that no improvement can be expected. (PACE 2010; 865–872)