Electromechanical Dyssynchrony Research Articles

Clinical Significance of Electromechanical Dyssynchrony and QRS Narrowing in Patients With Heart Failure Receiving Cardiac Resynchronization Therapy

BackgroundWe hypothesized that preoperative electromechanical dyssynchrony amenable to cardiac resynchronization therapy (CRT) and QRS narrowing immediately after CRT are both correlated and have a cumulative impact on response and outcome after CRT. MethodsA total of 233 CRT candidates (heart failure New York Heart Association classes II-IV, ejection fraction < 35%, QRS ≥ 120 milliseconds, 44% women, 71 ± 11 years old) were prospectively included. Preoperative electromechanical dyssynchrony amenable to CRT was assessed by septal deformation patterns using speckle tracking echocardiography. QRS narrowing was calculated from 12-lead electrocardiograms before and immediately after CRT implantation. The primary endpoint was overall mortality during long-term follow-up. The NTC clinical trial number is NCT02986633. ResultsEighty-seven percent of patients with preoperative electromechanical dyssynchrony experienced QRS narrowing after CRT (118/136), whereas 69% of patients without preoperative electromechanical dyssynchrony (67/97) experienced QRS narrowing after CRT (P < 0.001). By Cox multivariate analysis, both preoperative electromechanical dyssynchrony and lack of postoperative QRS narrowing were independently associated with an increased risk of mortality during follow-up (adjusted hazards ratio [HR] 2.24, 95% confidence interval [CI] 1.43-3.50 and HR 1.90, 95% CI 1.06-3.38, respectively). Compared with patients with preoperative electromechanical dyssynchrony, patients without both electromechanical dyssynchrony and postoperative QRS narrowing experienced a considerable increased risk of mortality during follow-up (adjusted HR 3.70, 95% CI 1.96-6.97). ConclusionsLack of postoperative QRS narrowing after CRT is associated with preoperative electromechanical dyssynchrony. Both preoperative electromechanical dyssynchrony and postoperative QRS narrowing have a favourable cumulative impact on outcome after CRT.

Quantification of Right Ventricular Electromechanical Dyssynchrony in Relation to Right Ventricular Function and Clinical Outcomes in Children with Repaired Tetralogy of Fallot

Electromechanical dyssynchrony occurs ubiquitously following tetralogy of Fallot (TOF) repair, manifesting electrically as a wide QRS duration and mechanically as a right-sided septal/apical flash. Early septal activation and prestretch of the right ventricular (RV) basal lateral wall followed by its postsystolic shortening contributes to inefficient RV mechanics. However, a right-sided septal flash is a dichotomous finding, and the severity of RV dyssynchrony as a continuous spectrum in relationship to RV dysfunction and clinical outcomes in patients with repaired TOF has not been studied. The aim of this study was to quantify the severity of electromechanical dyssynchrony in relation to RV remodeling and clinical outcomes in a pediatric cohort following TOF repair. A retrospective analysis was performed in 81 children with RV volume loading after TOF repair, aged 13.6±2.9years, and compared with 50 matched control subjects. Patients had higher RV basal-lateral prestretch and postsystolic strain amplitude and duration, RV mechanical dispersion, and basal lateral-septal wall delay compared with control subjects (P<.001 for all). All intra-RV dyssynchrony timing parameters were associated with reduced cardiac magnetic resonance-derived RV ejection fraction and/or echocardiography-derived RV longitudinal strain. Prestretch duration as a percentage of total shortening time and RV basal lateral-to-midseptal delay were independently associated with RV dysfunction. Postsystolic strain amplitude was higher in patients with ventricular arrhythmias compared with arrhythmia-free patients (7.8% [4.2%-13%] vs 2.0% [0%-12.5%], P=.03). RV prestretch duration, postsystolic strain, and RV lateral-septal delay quantify RV electromechanical dyssynchrony severity and reflect the underlying pathophysiology. The prestretch duration percentage and RV basal lateral-to-midseptal delay were independently associated with RV dysfunction, potentially providing a clinical tool to quantify RV electromechanical dyssynchrony.

His Bundle Pacing: Hemodynamics and Clinical Outcomes.

From 1993 to 2009, nearly 2.9 million pacemakers were implanted in the United States; the majority of which were dual-chamber pacemakers. One of the major physiologic advantages of dual-chamber pacing over single-chamber ventricular pacing is atrioventricular synchrony, which prevents the pacemaker syndrome. However, patients who are pacemaker dependent or use right ventricle (RV) apical pacing more than 40% of the time are at a risk of developing heart failure from electromechanical dyssynchrony. Studies have also shown that RV pacing results in nonphysiological activation of the left ventricle, leading to adverse clinical outcomes. Hence, alternative pacing sites, including the RV outflow tract, the high-RV septal region, bi-ventricular pacing, or His bundle pacing, have been explored for a better physiological electromechanical coupling of the ventricles. Although His bundle pacing has gained attention due to favorable data and clinical outcomes, it has not gained widespread acceptance into clinical practice. Hence, we aim to review the current experience with His bundle pacing and its clinical implications in this article.

Apical Transverse Motion Is Associated with Interventricular Mechanical Delay and Decreased Left Ventricular Function in Children with Dilated Cardiomyopathy

Apical transverse motion (ATM) is associated with electromechanical dyssynchrony in adult dilated cardiomyopathy (DCM). Bundle branch block electromechanical dyssynchrony is uncommon in pediatric DCM, but ATM and its association with ventricular function have not been characterized. Fifty-six children with DCM were retrospectively studied. Using echocardiography, ATM was assessed visually and by speckle-tracking longitudinal displacement of the interventricular septal and left ventricular (LV) lateral walls in opposite directions. Doppler tissue imaging-derived displacement and velocities were used to time the onset and peak LV and right ventricle motion, from which intra- and interventricular delays were calculated to assess their association with ATM. The timing of aortic valve opening and closure in relation to onset and peak LV displacement was used as a measure of LV mechanical efficiency. LV ATM was observed in 35 of 56 patients (62.5%), occurring in two patterns: 45% had ATM (interventricular septum displacing toward the lateral wall and lateral wall displacing toward the mitral annulus during systole), and 18% showed reverse ATM (r-ATM; lateral wall displaced toward the apex and interventricular septum displaced toward the septal annulus during systole). Both patterns were associated with increased interventricular but not intraventricular mechanical delay (controls: 2 msec, ATM 16 msec, r-ATM 8 msec, both P<.05 vs control subjects). Patients with ATM or r-ATM had lower LV ejection fractions (19% vs 29%, P<.05) and higher mechanical inefficiency compared with those without ATM. Survival was not statistically different in those with ATM or r-ATM compared with those without ATM or r-ATM. In pediatric DCM, ATM is associated with LV dysfunction, mechanical inefficiency, and interventricular mechanical delay.

Relationship of Electromechanical Dyssynchrony in Patients Submitted to CRT With LV Lead Implantation Guided by Gated Myocardial Perfusion Spect.

BackgroundHeart failure (HF) affects more than 5 million individuals in the United States, with more than 1 million hospital admissions per year. Cardiac resynchronization therapy (CRT) can benefit patients with advanced HF and prolonged QRS. A significant percentage of patients, however, does not respond to CRT. Electrical dyssynchrony isolated might not be a good predictor of response, and the last left ventricular (LV) segment to contract can influence the response.ObjectivesTo assess electromechanical dyssynchrony in CRT with LV lead implantation guided by GATED SPECT.MethodsThis study included 15 patients with functional class II-IV HF and clinically optimized, ejection fraction of 35%, sinus rhythm, left bundle-branch block, and QRS ≥ 120 ms. The patients underwent electrocardiography, answered the Minnesota Living with Heart Failure Questionnaire (MLHFQ), and underwent gated myocardial perfusion SPECT up to 4 weeks before CRT, being reassessed 6 months later. The primary analysis aimed at determining the proportion of patients with a reduction in QRS duration and favorable response to CRT, depending on concordance of the LV lead position, using chi-square test. The pre- and post-CRT variables were analyzed by use of Student t test, adopting the significance level of 5%.ResultsWe implanted 15 CRT devices, and 2 patients died during follow-up. The durations of the QRS (212 ms vs 136 ms) and the PR interval (179 ms vs 126 ms) were significantly reduced (p < 0.001). In 54% of the patients, the lead position was concordant with the maximal delay site. In the responder group, the lateral position was prevalent. The MLHFQ showed a significant improvement in quality of life (p < 0.0002).ConclusionCRT determines improvement in the quality of life and in electrical synchronism. Electromechanical synchronism relates to response to CRT. Positioning the LV lead in the maximal delay site has limitations.

Imaging in repaired tetralogy of Fallot with a focus on recent advances in echocardiography.

Imaging is essential for the management of adults with repaired tetralogy of Fallot (rToF). Echocardiography and cardiac magnetic resonance imaging are the central modalities to assess rToF. Here we review recent literature on imaging rToF, focusing on echocardiography and advances in assessment of cardiac mechanics. Several two-dimensional, three-dimensional, and Doppler echo parameters have been proposed to assess pulmonary regurgitation, right ventricular volumes and ejection fraction, but most of them still have important limitations in their feasibility and reliability compared to cardiac magnetic resonance (CMR). Myocardial deformation imaging to study ventricular and atrial mechanics, regional function, ventricular-ventricular interactions, and electro-mechanical dyssynchrony has yielded insights into the pathophysiologic mechanisms of right ventricular and left ventricular dysfunction; thereby predicting clinical outcomes and exercise capacity, allowing among others, evaluation of the impact of pulmonary valve replacement (PVR). Emerging technologies are expected to further our understanding of the drivers of dysfunction and guide indications and timing of PVR. Echocardiography and CMR have complementary and overlapping roles in rToF and contribute to our understanding of its pathophysiology and management.

Acute right ventricular resynchronization improves haemodynamics in children after surgical repair of tetralogy of Fallot.

Right bundle branch block is associated with right ventricular (RV) electromechanical dyssynchrony, which may contribute to acute haemodynamic impairment after repair of tetralogy of Fallot (ToF). We sought to evaluate the effects of RV resynchronization on haemodynamics and tissue oxygenation during the first 24 h after surgery. Arterial pressures, cardiac output, and tissue oxygenation were measured in 28 consecutive patients (median age 10.1 months) during baseline sinus rhythm with right bundle branch block and after RV resynchronization by atrial-triggered RV free wall pacing in complete fusion with spontaneous activation. Studied variables were compared in a crossover design in four 5-min intervals (baseline rhythm and stimulation, 2x each). Resynchronization reduced the QRS complex duration from median 110 to 70 ms (P < 0.001), increased significantly median arterial systolic, mean and pulse pressure, cardiac index, left ventricular maximum +dP/dT and decreased central venous pressure (P < 0.001 for all). Both cerebral and renal oxygenation improved (P < 0.001). Eleven of the 28 patients showed a clinically highly significant resynchronization effect defined as an increase in arterial pulse pressure of ≥ 10%. The q-RV interval (expressed as % of QRS duration) at the RV pacing site during baseline rhythm was the only predictor of resynchronization effect. RV resynchronization carried short-term improvement of haemodynamics in children early after surgery for ToF and might be a useful non-pharmacologic adjunct to the management of haemodynamically compromised patients. Resynchronization effect was maximized when pacing from area of the latest RV activation.

Role of echocardiography before cardiac resynchronization therapy: new advances and current developments.

The role of echocardiography in improving the selection of patients who will benefit from cardiac resynchronization therapy (CRT) remains a source of debate. Although previous landmark reports have demonstrated a link between mechanical dyssynchrony, assessed by delays between left ventricle (LV) walls and response to CRT, the predictive value of these findings has not yet been confirmed in multicenter trials. Indeed, recent studies demonstrated that the classical assessment of LV mechanical dyssynchrony using delay between walls by echocardiography depends not only on LV electrical activation delay (electrical dyssynchrony), but also on abnormalities in regional contractility of the LV and/or loading conditions, which do not represent an appropriate target for CRT. Recent reports highlighted the value of new indices of electromechanical dyssynchrony obtained by echocardiography, to predict LV response and outcome after CRT including septal flash, left bundle branch block-typical pattern by longitudinal strain, apical rocking, septal strain patterns, and systolic stretch index. This was achieved using a mechanistic approach, based on the contractile consequences of electrical dyssynchrony. These indices are rarely found in patients with narrow QRS (<120ms), whereas their frequency rises in patients with an increase in QRS duration (>120ms). Theses indices should improve candidate selection for CRT in clinical practice, especially for patients in whom the benefit of CRT remains uncertain, for example, patients with intermediate QRS width (120-150ms).

Dyssynchrony and electromechanical delay are associated with focal fibrosis in the systemic right ventricle — Insights from echocardiography

BackgroundSystemic right ventricular (RV) dysfunction and sudden cardiac death remain problematic late after Mustard operation for transposition of the great arteries. The exact mechanism for that relationship is likely to be multifactorial including myocardial fibrosis. Doppler echocardiography gives further insights into the role of fibrosis shown by late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) in late morbidity. Methods and resultsTwenty-two consecutive patients, mean age 28±8years, were studied with 2D echocardiography, and also assessed by LGE CMR. The presence of LGE in 13/22 patients (59%) was related to delayed septal shortening and lengthening (P=0.002 &P=0.049), prolonged systemic RV isovolumic contraction time (P=0.024) and reduced systemic RV free wall and septal excursion (P=0.027 &P=0.005). The systemic RV total isovolumic time was prolonged but not related to extent of LGE. LGE extent was related to markers of electromechanical delay and dyssynchrony (delayed onset of RV free wall shortening and lengthening; r=0.73 &P=0.004 and r=0.62 &P=0.041, respectively, and QRS duration r=0.68, P<0.01) and was inversely related to systolic RV free wall shortening velocity (r=−0.59 &P=0.042). The presence of LGE was also related to lower exercise capacity, ≥mild tricuspid regurgitation and more arrhythmia (P=0.008, P=0.014 and P=0.040). RV free wall excursion and systolic tissue Doppler velocity were related to CMR derived RV ejection fraction (r=0.51, P=0.015, and r=0.77, P=<0.001, respectively). ConclusionPost Mustard repair, myocardial fibrosis is related to dyssynchrony, RV long axis dysfunction and tricuspid regurgitation. Echocardiographic measurements of systemic RV function can be confidently used in serial follow-up following Mustard operation.

Cardiac resynchronization therapy in congenital heartdisease.

Cardiac resynchronization therapy (CRT) is an established treatment option for adult patients suffering heart failure due to idiopathic or ischemic cardiomyopathy associated with electromechanical dyssynchrony. There is limited evidence suggesting similar efficacy of CRT in patients with congenital heart disease (CHD). Due to the heterogeneity of structural and functional substrates, CRT implantation techniques are different with athoracotomy or hybrid approach prevailing. Efficacy of CRT in CHD seems to depend on the anatomy of the systemic ventricle with best results achieved in systemic left ventricular patients upgraded to CRT from conventional pacing. Indications for CRT in patients with CHD were recently summarized in the Pediatric and Congenital Electrophysiology Society (PACES) and the Heart Rhythm Society (HRS) Expert Consensus Statement on the Recognition and Management of Arrhythmias in Adult Congenital Heart Disease and are presented in the text.

Fragmented QRS as a Marker of Electrical Dyssynchrony to Predict Inter-Ventricular Conduction Defect by Subsequent Echocardiographic Assessment in Symptomatic Patients of Non-Ischemic Dilated Cardiomyopathy.

BackgroundLeft ventricular (LV) dyssynchrony frequently occurs in patients with heart failure (HF). QRS ≥ 120 ms is a surrogate marker of electrical dyssynchrony, which occurs in only 30% of HF patients. In contrary, in those with normal QRS (nQRS) duration, LV dyssynchrony has been reported in 20-50%. This study was carried out to investigate the role of fragmented QRS (fQRS) on the surface electrocardiography (ECG) as a marker of electrical dyssynchrony to predict the presence of significant intraventricular dyssynchrony (IVD) by subsequent echocardiographic assessment.MethodsA total of 226 consecutive patients with non-ischemic cardiomyopathy were assessed for fQRS on surface ECG as defined by presence of an additional R wave (R prime), notching in nadir of the S wave, notching of R wave, or the presence of more than one R prime (fragmentation) in two contiguous leads corresponding to a major myocardial segment. Tissue Doppler imaging (TDI) was performed in the apical views (four-chamber, two-chamber and long-axis) to analyze all 12 segments at both basal and middle levels. Time-to-peak myocardial sustained systolic (Ts) velocities were calculated. Significant systolic IVD was defined as Ts-SD > 32.6 ms as known as “Yu index”.ResultOf the total patients, 112 had fQRS (49.5%), while 114 had nQRS (50.5%) with male dominance (M/F = 71:29). Majority of patients were in NYHA class II (n = 122, 54%) followed by class III (n = 83; 37%), and class IV (n = 21; 9%). There were no significant differences among both groups for baseline parameters except higher QRS duration (102.42 ± 14.05 vs. 91.10 ± 13.75 ms; P = 0.001), higher Yu index (35.64 ± 12.79 vs. 20.45 ± 11.17; P = 0.01) and number of patients with positive Yu index (78.6% vs. 21.1%; P = 0.04) in group with fQRS compared with group with nQRS. fQRS complexes had 84.61% sensitivity and 80.32% specificity with positive predictive value of 78.6% and negative predictive value of 85.9% to detect IVD. On detailed segmental analysis for fQRS distribution, inferior segment had maximum (37%), followed by anterior (23%), lateral (19%), inferior and lateral (11%), anterior and inferior (8%), and anterior and lateral (2%). Among 104 patients with significant dyssynchrony, 88 patients (84.6%) had fQRS in the dyssynchronic segment.ConclusionFragmentation of QRS complex is an important predictor of electro-mechanical dyssynchrony. It is also helpful in localizing the dyssynchronous segment. In future, larger studies may be carried out to investigate the role of fQRS as a predictor of response to cardiac resynchronization therapy (CRT) in this subgroup of HF patients with narrow QRS.

Low-dose dobutamine stress echo for reverse remodeling prediction after cardiac resynchronization

PurposeCardiac resynchronization therapy (CRT) is a valuable option for patients with heart failure and wide QRS to reduce electromechanical dyssynchrony (DYS). High non-responders rate (30%) urges the need to improve selection of candidates for CRT. We hypothesized that low-dose dobutamine stress echocardiography (DSE) can help unmask dyssynchronous motion. The aim of this study is comparison between dyssynchrony index at rest and during low-dose dobutamine stress to predict left ventricular reverse remodeling after CRT. Patients and methodsProspectively, 57 consecutive patients (37 male) aged 61.8±9 who qualified for CRT according to current guidelines were enrolled. Two dimensional echocardiography and tissue Doppler imaging (TDI) were performed before and 6 month after CRT to assess reverse remodeling (rLV). Additionally DSE was performed before CRT. DYS was assessed at rest (DYSr) and peak DSE (DYSd) separately, as a difference between time to peak systolic velocity (Ts) of septum and lateral wall. Ts was corrected for heart rate. ResultsrLV defined as decrease ≥15% of LVESV at follow-up was found in 38 (67%) patients. DYSr and DYSd were independent predictors of rLV (OR=1.04, Cl ±1.02–1.06, p<0.02 and OR=1.05, Cl±1.03–1.08, p<0.0002 respectively). ROC analysis found that DYSr>42ms and DYSd>59ms had sensitivity of 70% and 87%, specificity of 61% and 78%, and accuracy of 70% and 84% respectively for prediction of reverse remodeling LV. Area under Receiver Operating Characteristic Curve for DYSd was higher than for DYSr (0.89 vs 0.71, p<0.007). ConclusionExercise intraventricular dyssynchrony assessed by dobutamine stress echo is a strong independent predictor of cardiac resynchronization therapy response.

Metabolic remodeling in moderate synchronous versus dyssynchronous pacing-induced heart failure: integrated metabolomics and proteomics study.

Heart failure (HF) is accompanied by complex alterations in myocardial energy metabolism. Up to 40% of HF patients have dyssynchronous ventricular contraction, which is an independent indicator of mortality. We hypothesized that electromechanical dyssynchrony significantly affects metabolic remodeling in the course of HF. We used a canine model of tachypacing-induced HF. Animals were paced at 200 bpm for 6 weeks either in the right atrium (synchronous HF, SHF) or in the right ventricle (dyssynchronous HF, DHF). We collected biopsies from left ventricular apex and performed comprehensive metabolic pathway analysis using multi-platform metabolomics (GC/MS; MS/MS; HPLC) and LC-MS/MS label-free proteomics. We found important differences in metabolic remodeling between SHF and DHF. As compared to Control, ATP, phosphocreatine (PCr), creatine, and PCr/ATP (prognostic indicator of mortality in HF patients) were all significantly reduced in DHF, but not SHF. In addition, the myocardial levels of carnitine (mitochondrial fatty acid carrier) and fatty acids (12:0, 14:0) were significantly reduced in DHF, but not SHF. Carnitine parmitoyltransferase I, a key regulatory enzyme of fatty acid ß-oxidation, was significantly upregulated in SHF but was not different in DHF, as compared to Control. Both SHF and DHF exhibited a reduction, but to a different degree, in creatine and the intermediates of glycolysis and the TCA cycle. In contrast to this, the enzymes of creatine kinase shuttle were upregulated, and the enzymes of glycolysis and the TCA cycle were predominantly upregulated or unchanged in both SHF and DHF. These data suggest a systemic mismatch between substrate supply and demand in pacing-induced HF. The energy deficit observed in DHF, but not in SHF, may be associated with a critical decrease in fatty acid delivery to the ß-oxidation pipeline, primarily due to a reduction in myocardial carnitine content.

Кардиоресинхронизирующая терапия в лечении сердечной недостаточности у детей

Cardiac resynchronizing therapy (CRT) is currently a leading approach to the treatment of heart failure in adults. However, data regarding application of CRT in children remain limited and indications for CRT are unclear. There is evidence that the best treatment outcomes result from the administration of CRT to the group of children whose heart failure is caused by dyssynchrony mediated by traditional stimulation of the right ventricle in patient with complete atrioventricular block. On the contrary, the presence of dilated cardiomyopathy and functional class III-IV heart failure are the predictors of ineffective CRT. Implantation of CRT devices in children has many peculiarities and challenges associated with anatomic and physiological characteristics of childhood age. Taking into consideration the expected length of treatment, one should admit that epicardial biventricular stimulation should be preferred. In the present paper the authors discuss pathophysiology of the electromechanical dyssynchrony, analyze their own experience with CRT, and suggest indications for this kind of treatment.

Relationships between P wave dispersion, atrial electromechanical delay, left atrial remodeling, and NT-proBNP levels, in patients with hypertrophic cardiomyopathy

We evaluated the associations among the well-known atrial fibrillation (AF) predictors including P-wave dispersion (PWD), intra- and inter-atrial electromechanical dyssynchrony (EMD), left atrial (LA) phasic functions, and plasma N-terminal prohormone of B-type natriuretic peptide (NT-proBNP) levels, in patients with hypertrophic cardiomyopathy (HCM). Seventy patients with HCM and age and sex matched 70 subjects were enrolled. PWD, LA total emptying fraction (LATEFr), active emptying fraction (LAAEFr), passive emptying fraction (LAPEFr), expansion index (LAEI) intra- and inter-atrial EMD were calculated. Levels of NT-proBNP of all subjects were determined. Higher PWD (p = 0.006), significantly decreased LAEI (p < 0.001), LATEFr, and LAPEFr (both p values < 0.001) values and significantly increased inter-atrial (p < 0.001), LA (p = 0.001), and right atrial dyssynchrony (p < 0.001) were observed in the HCM group compared to controls. PWD was negatively correlated with LAEI (r = -0.236, p = 0.005) and LATEFr (r = -0.242, p = 0.04), however not with LAPEFr (p = 0.7), or LAAEFr (p = 0.3). Except for the LA lateral wall PA' (r = 0.283, p = 0.02), PWD was not correlated with any atrial EMD parameter. Inter-atrial dyssynchrony was related to LAEI (r = -0.272, p = 0.001), LATEFr (r = -0.256, p = 0.03), and LAPEFr (r = -0.332, p = 0.006), but not, however, to LAAEFr (p = 0.4). The plasma NT-proBNP levels of patients were not correlated with either PWD (p = 0.927) or inter-atrial dyssynchrony (p = 0.102). PWD and inter-atrial dysynchrony seem to independently promote AF, although both are associated with LA reservoir function in HCM populations. The NT-proBNP level is not associated with these two AF predictors in patients with HCM. NT-proBNP seems to be a poor marker of atrial electrical remodeling in HCM patients.

Efficacy of cardiac resynchronization in acutely infarcted canine hearts with electromechanical dyssynchrony.

Patients with acute myocardial infarction (MI), left bundle branch block (LBBB), and marked left ventricular (LV) decompensation suffer from nearly 50% early mortality. Whether cardiac resynchronization therapy (CRT) improves hemodynamic status in this condition is unknown. We tested CRT in this setting by using a canine model of delayed lateral wall (LW) activation combined with 2 hours of coronary artery occlusion-reperfusion. This study aimed to evaluate the acute hemodynamic effects of CRT during and immediately after MI. Adult dogs (n = 8) underwent open-chest 2-hour mid-left anterior descending artery occlusion followed by 1-hour reperfusion. Four pacing modes were compared: right atrial pacing, pseudo-left bundle block (right ventricular pacing), and CRT with the LV lead positioned at either the LW (LW-CRT) or the peri-infarct zone (peri-infarct zone-CRT). Continuous LV pressure-volume data, regional segment length, and proximal left anterior descending flow rates were recorded. At baseline, both right ventricular pacing and peri-infarct zone CRT reduced anterior wall regional work by ~50% (vs right atrial pacing). During coronary occlusion, this territory became dyskinetic, and dyskinesis rose further with both CRT modes as compared to pseudo-LBBB. Global cardiac output, stroke work, and ejection fraction all still improved by 11%-23%. After reperfusion, both CRT modes elevated infarct zone regional work and blood flow by ~10% as compared to pseudo-LBBB, as well as improved global function. CRT improves global chamber systolic function in left ventricles with delayed LW activation during and after sustained coronary occlusion. It does so while modestly augmenting infarct zone dyskinesis during occlusion and improving regional function and blood flow after reperfusion. These findings support CRT in the setting of early post-MI dyssynchronous heart failure.

Cardiac resynchronization therapy for pediatric patients with heart failure and congenital heart disease: a reappraisal of results.

Cardiac resynchronization therapy (CRT) is an effective treatment for adult patients with left ventricular (LV) failure. Large prospective, randomized, controlled trials have demonstrated that CRT results in improvement in cardiac function, LV reverse remodeling, decreased hospitalizations for heart failure (HF), improved quality of life, and decreased overall mortality.1–5 However, 30% of adult patients are nonresponders to CRT, spurring further evaluation of electromechanical dyssynchrony to determine optimal pacing sites and to improve CRT selection criteria for maximal response.1,6 The positive response in adult HF prompted exploration of the use of CRT in pediatric HF patients. However, the effectiveness of CRT in the pediatric population is difficult to evaluate because of the complex anatomic substrates of congenital heart disease (CHD) and scar formation from multiple cardiac surgeries with a higher proportion of right bundle-branch block (RBBB) and right ventricular (RV) failure than in the adult population. The typical adult HF scenario of an LV ejection fraction (EF) ≤35% with a left bundle-branch block (LBBB) is uncommon in children; therefore, the adult selection criteria for CRT cannot be easily translated to pediatric patients. Furthermore, a small heterogeneous pediatric patient population hinders a systematic assessment of long-term benefit from CRT. In the normal heart, ventricular electrical activation spreads through the His-Purkinje system, which has unique rapid propagation properties and widespread distribution. This allows highly coordinated electrical activation between distant regions of both ventricles, resulting in highly synchronous mechanical contraction. Given the strong relationship between electrical excitation and mechanical contraction in the myocardium, it is not surprising that abnormal electrical activation results in abnormal mechanical contraction.7,8 During a spontaneous or pacing-induced bundle-branch block, ventricular activation spreads primarily cell to cell through the surrounding myocardium, which can be up to 4 times slower than the specialized His-Purkinje …

Mechanisms of right ventricular electromechanical dyssynchrony and mechanical inefficiency in children after repair of tetralogy of fallot.

Right bundle branch block and right ventricular (RV) dysfunction are common after tetralogy of Fallot repair (rTOF). We hypothesized that right bundle branch block is associated with specific RV mechanical dyssynchrony and inefficient contraction. We studied rTOF children and age-matched controls. QRS duration and morphology were assessed. RV mechanical dyssynchrony, indicated by early septal activation (right-sided septal flash), RV lateral wall prestretch/late contraction, postsystolic shortening, and intraventricular delay were analyzed using 2-dimensional strain echocardiography. Peak oxygen consumption reflected exercise capacity. Pulmonary regurgitation and RV volumes were assessed by MRI. Forty-six rTOF patients and 46 controls were studied. Ninety-three percent of rTOF patients demonstrated a right-sided septal flash with simultaneous RV basal lateral wall prestretch/late activation. The RV basal segment was the most delayed in onset (115 [0-194] versus 35 [0-96] ms) and termination (462 [369-706] versus 412 [325-529] ms) of longitudinal shortening, with postsystolic shortening. QRS duration correlated with RV basal time to onset and peak shortening (P<0.05). Intra-RV delay was higher in rTOF (P<0.05) in association with RV dilatation (r=0.33; P=0.04). In rTOF, RV mechanics were inefficient, with prestretch and postsystolic shortening comprising 15±11% and 16±9% of total shortening, respectively. A composite parameter of electric and mechanical dyssynchrony correlated with RV end-diastolic volume (r=0.39; P=0.03). Typical electromechanical dyssynchrony associated with mechanical inefficiency, regional dysfunction, and RV dilatation is common in rTOF children, possibly contributing to progressive RV dysfunction. The potential of cardiac resynchronization in appropriate patients requires further study.

Cardiac Resynchronization Therapy in Patients with Challenging Anatomy Due to Venous Anomalies or Adult Congenital Heart Disease

Cardiac resynchronization therapy (CRT) has proven salutary effects in patients with congestive heart failure, systolic dysfunction, and electromechanical dyssynchrony in the setting of ischemic, nonischemic, and congenital cardiomyopathy. While CRT device implants have become routine in the adult ischemic or nonischemic cardiomyopathy populations, patients with congenital heart disease offer special challenges due to unusual anatomic variations. A comprehensive assessment of anatomic abnormalities is essential prior to implant. In addition, implant techniques and equipment must be tailored to the expected anatomy. A flexible approach is necessary-implant may require equipment and techniques adapted from vascular intervention. This article describes our approach to CRT implant in patients with congenital heart disease, and is illustrated by reports of several cases.

Alternative Sites for Right Ventricular Pacing in Chagas Disease: A Comparative Study of the Mid‐Septum and Inflow Tract

The right ventricular mid-septum and inflow tract are alternative pacing sites that are potentially less harmful to cardiac function. This study aimed to analyze the influence of these two alternative pacing sites on the clinical course of patients with chronic Chagas disease, who underwent definitive pacemaker implantation. A total of 80 patients with Chagas disease and classical indications for definitive pacemaker implantation were randomized into two groups between October 2008 and August 2010: 40 received inflow tract implantation and 40 patients received mid-septum implantation. The analyzed parameters included: (1) progression stage of chronic chagasic cardiomyopathy (CCC), (2) electrocardiographic analysis, (3) left ventricular remodeling, and (4) electromechanical dyssynchrony. The assessment was performed 24-48 hours after implantation and a follow-up period of 18 months. Compared with inflow tract implantation, mid-septum implantation was associated with slower CCC progression and the generation of narrower QRS complexes (131.8 ± 8.4 milliseconds vs 150.5 ± 10.5 milliseconds; P < 0.01). No left ventricular remodeling was detected. Intraventricular dyssynchrony was more frequent in the inflow tract group than in the mid-septum group (85% vs 32.5%, respectively; odds ratio [OR], 9.15; P = 0.02) as was interventricular dyssynchrony (37.5% vs 17.5%, respectively; OR, 2.83; P < 0.01). Mid-septum implantation was associated with slower CCC progression, generation of narrower QRS complexes, and lower electromechanical dyssynchrony, suggesting that this pacing site could be less harmful to cardiac function than the inflow tract site in patients with CCC.