Short Atrioventricular Delay Research Articles

Determinants of the time-to-peak left ventricular dP/dt (Td) and QRS duration with different fusion strategies in cardiac resynchronization therapy.

BackgroundCardiac resynchronization therapy (CRT) is helpful in selected patients; however, responder rates rarely exceed 70%. Optimization of CRT may therefore benefit a large number of patients. Time-to-peak dP/dt (Td) is a novel marker of myocardial synergy that reflects the degree of myocardial dyssynchrony with the potential to guide and optimize treatment with CRT. Optimal electrical activation is a prerequisite for CRT to be effective. Electrical activation can be altered by changing the electrical wave-front fusion resulting from pacing to optimize resynchronization. We designed this study to understand the acute effects of different electrical wave-front fusion strategies and LV pre-/postexcitation on Td and QRS duration (QRSd). A better understanding of measuring and optimizing resynchronization can help improve the benefits of CRT.MethodsTd and QRSd were measured in 19 patients undergoing a CRT implantation. Two biventricular pacing groups were compared: pacing the left ventricle (LV) with fusion with intrinsic right ventricular activation (FUSION group) and pacing the LV and right ventricle (RV) at short atrioventricular delay (STANDARD group) to avoid fusion with intrinsic RV activation. A quadripolar LV lead enabled pacing from widely separated electrodes; distal (DIST), proximal (PROX) and both electrodes combined (multipoint pacing, MPP). The LV was stimulated relative in time to RV activation (either RV pace-onset or QRS-onset), with the LV stimulated prior to (PRE), simultaneous with (SIM) or after (POST) RV activation. In addition, we analyzed the interactions of the two groups (FUSION/STANDARD) with three different electrode configurations (DIST, PROX, MPP), each paced with three different degrees of LV pre-/postexcitation (PRE, SIM, POST) in a statistical model.ResultsWe found that FUSION provided shorter Td and QRSd than STANDARD, MPP provided shorter Td and QRSd than DIST and PROX, and SIM provided both the shortest QRSd and Td compared to PRE and POST. The interaction analysis revealed that pacing MPP with fusion with intrinsic RV activation simultaneous with the onset of the QRS complex (MPP*FUSION*SIM) shortened QRSd and Td the most compared to all other modes and configurations. The difference in QRSd and Td from their respective references were significantly correlated (β = 1, R = 0.9, p < 0.01).ConclusionPacing modes and electrode configurations designed to optimize electrical wave-front fusion (intrinsic RV activation, LV multipoint pacing and simultaneous RV and LV activation) shorten QRSd and Td the most. As demonstrated in this study, electrical and mechanical measures of resynchronization are highly correlated. Therefore, Td can potentially serve as a marker for CRT optimization.

Morbidity and resource usage after myectomy- or pacing-treatment in hypertrophic obstructive cardiomyopathy: A case-control study

BackgroundTreatment of left ventricular outflow-obstruction (LVOTO) in hypertrophic obstructive cardiomyopathy (HOCM) by short atrio-ventricular delay pacing has long-term hemodynamic results that are not inferior to myectomy, but publications comparing long-term morbidity following those treatments are lacking. MethodsA search for HOCM-patients attending all ten hospitals in the West Götaland Region, Sweden, from 2002 through 2013, identified 251 patients (42 treated with myectomy, 88 with pacing and 121 conservatively). As the age at procedure was significantly lower in the myectomy-group compared to the pacing-group, morbidity was compared by case-control methodology, matching patients for age, maximal wall thickness and LVOT-gradient. We found 31 pairs who constituted the comparison-groups. Post-intervention median follow-up was 15.4 and 10.4 years in pacing- and myectomy-group, respectively. Post-procedural and long-term complications and re-interventions, length of stay, and cost of hospitalization were documented. ResultsBoth treatments improved New York Heart Association class and LVOT-gradients significantly. There were fewer peri-procedural complications in the pacing-group compared to myectomy-group (3.2% and 35.5% p < 0.001). During follow-up pacemaker was implanted in 35.5% of myectomy-group for atrio-ventricular block, 9.7% peri-operatively, and 25.8% during late-follow-up. Furthermore, the pacing group had a superior freedom from all re-interventions, 90.3% versus 61.3% in myectomy-group (p = 0.003). Pacing patients had a shorter in-hospital stay (median 4 [IQR = 2] days) compared to myectomy 11 [7] days; P < 0.001). The mean cost of hospitalization was 74,000 ± 16,000 SEK for pacing and 310,000 ± 180,000 SEK for myectomy, p < 0.001. ConclusionPacing is a simple and reliable treatment for drug-refractory HOCM-patients with low rate of complications and costs.

Electrical wavefront fusion in heart failure patients with left bundle branch block and cardiac resynchronization therapy: Implications for optimization

BackgroundNovel metrics of electrical dyssynchrony based on multi-electrode mapping and ECG-based markers of fusion are better predictors of cardiac resynchronization therapy (CRT) response than QRS duration. ObjectiveTo describe a new methodology for measuring electrical synchrony based on wavefront fusion and electrocardiographic cancellation in patients with CRT and its potential for CRT optimization. MethodsPatients with left bundle branch block (LBBB) type conduction and CRT (n = 84) were studied at multiple device settings using an ECG belt (53 anterior and posterior electrodes). The area between combinations of anterior and posterior curves (AUC) was calculated and cardiac resynchronization index (CRI) defined as percent change in AUC compared to LBBB. ResultsIn 14 patients with complete heart block or atrial fibrillation, CRI at optimal ventriculo-ventricular delay (VVD) (40 ± 19 ms) was significantly higher than with simultaneous biventricular pacing (BiVp) (90 ± 8.6% vs. 54.2 ± 24.2%, p < 0.001). In all 70 patients paced LV-only, LV-paced wavefront was ahead of native wavefront at short atrio-ventricular delay (AVD) and CRI increased with increase in AVD, peaked, and then decreased. Optimal CRI during LV-only pacing was significantly better than optimal CRI with simultaneous BiVp (89.6 ± 8% vs. 64.4 ± 22%, p < 0.001), and occurred at AVD 68 ± 22 ms less than the atrial-RV sensed interval. With sequential BiVp, best CRI was 83.9 ± 13% (with LV preactivation of 40 ± 20 ms). Best CRI at any setting was markedly better than CRI at standard setting (91.6 ± 7.7% vs. 52.7 ± 23.3, p < 0.001). ConclusionWe describe a novel non-invasive investigational tool that quantifies wavefront fusion and electrical dyssynchrony, and may allow for individualized CRT optimization.

Left Ventricular Outflow Obstruction After TAVR Due to Systolic Anterior Motion Successfully Treated With Cardiac Pacing

Abstract Left ventricle outflow tract obstruction can have catastrophic hemodynamical consequences. Patients with severe aortic stenosis undergoing transcatheter aortic valve replacement are at risk of developing this serious complication in the postprocedural period. We present how a drug refractory left ventricle outflow tract obstruction, observed in a 76 year old female after transcatheter aortic valve replacement, was successfully treated with permanent atrioventricular pacing. After the procedure we observed an increase of gradients in left ventricle outflow tract to maximal gradient 96mmHg and mean gradient 46mmHg. The mechanism of left ventricle outflow tract obstruction was systolic anterior motion of the mitral valve. Despite fluids and increased dose of beta-blocker the was no improvement on control echocardiography. A decision to implant a dual chamber pacemaker was made in order to try do decrease the gradients. An immediate decrease in left ventricle outflow tract gradients after activation of sequential pacing with short atrioventricular delay was observed. Awareness of this method may prove helpful to cardiothoracic anesthesiologists treating patients after transcatheter aortic valve replacement

Characteristics of Cardiac Memory in Patients with Implanted Cardioverter-defibrillators: The Cardiac Memory with Implantable Cardioverter-defibrillator (CAMI) Study.

This study sought to determine factors associated with cardiac memory (CM) in patients with implantable cardioverter-defibrillators (ICDs). Patients with structural heart disease [n = 20; mean age: 72.6 ± 11.6 years; 80% male; mean left ventricular ejection fraction (LVEF): 31.7 ± 7.6%; history of myocardial infarction in 75% and nonsustained ventricular tachycardia (NSVT) in 85%] and preserved atrioventricular conduction received dual-chamber ICDs for primary (80%) or secondary (20%) prevention. Standard 12-lead electrocardiograms were recorded in AAI and DDD modes before and after seven days of right ventricular (RV) pacing in DDD mode with a short atrioventricular delay. The direction (azimuth and elevation) and magnitude of spatial QRS, T, and spatial ventricular gradient vectors were measured before and after seven days of RV pacing. CM was quantified as the degree of alignment between QRSDDD-7 and TAAI-7 vectors (QRSDDD-7 –TAAI-7 angle). Circular statistics and mixed models with a random slope and intercept were adjusted for changes in cardiac activation, LVEF, known risk factors, and the use of medications known to affect CM occurring on days 1 through 7. The QRSDDD-7–TAAI-7 angle strongly correlated (circular r = −0.972; p < 0.0001) with a TAAI-7–TDDD-7 angle. In the mixed models, CM-T azimuth changes [+132° (95% confidence interval (CI): 80°–184°); p < 0.0001] were counteracted by the history of MI [−180° (95% CI: −320° to −40°); p = 0.011] and female sex [−162° (95% CI: −268° to −55°); p = 0.003]. A CM-T area increase [+15 (95% CI: 6–24) mV*ms; p < 0.0001] was amplified by NSVT history [+27 (95% CI: 4–46) mV*ms; p = 0.007]. These findings suggest that preexistent electrical remodeling affects CM in response to RV pacing, that CM exhibits saturation behavior, and that women reach CM saturation more easily than men.

Factors influencing long-term heart failure mortality in patients with obstructive hypertrophic cardiomyopathy in Western Sweden: probable dose-related protection from beta-blocker therapy.

ObjectiveIn order to avoid effects of referral bias, we assessed risk factors for disease-related mortality in a geographical cohort of patients with hypertrophic obstructive cardiomyopathy (HOCM), and any therapy effect on survival.MethodsDiagnostic databases in 10 hospitals in the West Götaland Region yielded 251 adult patients with HOCM (128 male, 123 female). Case notes were reviewed for clinical data and ECG and ultrasound findings. Beta-blockers were used in 71.3% of patients from diagnosis (median metoprolol-equivalent dose of 125 mg/day), and at latest follow-up in 86.1%; 121 patients had medical therapy alone, 88 short atrioventricular delay pacing and 42 surgical myectomy. Mean follow-up was 14.4±8.9 (mean±SD) years. Primary endpoint was disease-related death, and secondary endpoint heart failure deaths.ResultsThere were 65 primary endpoint events. Independent risk factors for disease-related death on multivariate Cox hazard regression were: female sex (p=0.005), age at diagnosis (p<0.001), outflow gradient ≥50 mm Hg at diagnosis (p=0.036) and at follow-up (p=0.001). Heart failure caused 62% of deaths, and sudden cardiac death 17%. Late independent predictors of heart failure death were: female sex (p=0.003), outflow gradient ≥50 mm Hg at latest follow-up (p=0.032), verapamil/diltiazem therapy (p=0.012) and coexisting hypertension (p=0.031), but not other comorbidities. Neither myectomy nor pacing modified survival, but early and maintained beta-blocker therapy was associated with dose-dependent reduction in disease-related mortality in the multivariate model (p=0.028), and final dose was also associated with reduced heart failure mortality (p=0.008). Kaplan-Meier survival curves analysed in initial dose bands of 0–74, 75–149 and ≥150 mg metoprolol/day showed 10-year freedom from disease-related deaths of 83.1%, 90.7% and 97.0%, respectively (ptrend=0.00008). Even after successful relief of outflow obstruction by intervention, there was survival benefit of metoprolol doses ≥100 mg/day (p=0.01).ConclusionsIn population-based HOCM cohorts heart failure is a dominant cause of death and on multivariate analysis beta-blocker therapy was associated with a dose-dependent cardioprotective effect on total, disease-related as well as heart failure-related mortality.

Energy Dissipation in Resynchronization Therapy: Impact of Atrioventricular Delay

Optimal atrioventricular delay (AVD) achieves maximum cardiac output in patients undergoing cardiac resynchronization therapy (CRT). Nonoptimal AVD decreases left ventricular (LV) end-diastolic volume and causes loss of flow momentum prior to LV ejection. We investigated the potential role of energy dissipation (ED) in these changes in cardiac output through the study of intraventricular flow. We hypothesized that short and long AVD increases ED when compared with optimal AVD by altering the physiologic flow mechanics that preserve kinetic energy in the LV. Forty-four patients under CRT underwent echocardiographic LV flow analysis under optimal, short, and long AVD. LV ED and vortical flow in the inflow-outflow tract were studied during the end-diastolic and early systolic period, and paired comparisons were obtained between optimal and nonoptimal values. ED in the left ventricle was minimal in optimal AVD and significantly increased with nonoptimal values (79.1±27.5J/m·sec inoptimal AVD vs 96.5±34.7J/m·sec in short AVD; n=18, P=.006; 123.3±67.6J/m·sec in optimal AVD vs 292.4±202.5J/m·sec in long AVD; P<.001). Increase in ED occurred due to inadequate flow redirection toward the outflow tract in short AVD and due to both turbulence and prolonged ineffective flow rotation in long AVD. Optimal AVD in resynchronization therapy favors physiological vortex flow patterns in the left ventricle during the end-diastolic and early systolic period. These patterns are altered when nonoptimal values are programmed, increasing ED.

Short atrioventricular delay pacing therapy in young and old patients with hypertrophic obstructive cardiomyopathy: good long-term results and a low need for reinterventions.

AimsExamination of long-term results following different treatments in hypertrophic obstructive cardiomyopathy (HOCM) in a complete geographical cohort.Methods and resultsHOCM patients attending during 2002–13 in all 10 hospitals in the West Götaland Region, Sweden, were identified (n = 251), follow-up 14.4 (±8.9) years (mean ± SD), 121 managed medically, 42 treated with myectomy and 88 with short atrioventricular (AV) delay pacing as first interventional procedure. Post-intervention follow-up was 12.9 ± 8.7 years and 12.2 ± 5.0 years, respectively. Both intervention treatments improved New York Heart Association (NYHA) class and outflow gradients significantly. Patients treated with pacing were older (median age 64 vs. 43 years, P < 0.001). Freedom from disease-related death post-procedure at 5, 10, and 20 years were 93%, 80%, 56% vs. 93%, 93%, 57% in pacing and myectomy groups, respectively (log-rank P = 0.43). Survival after diagnosis was not different in patients just treated conservatively (P = 0.51 pacing/conservative; P = 0.39 myectomy/conservative). Reintervention for outflow gradients in patients ≥18 years at procedure occurred in 3.5% in pacing group and 15.6% in myectomy group (P = 0.007). Pacing therapy was equally effective in patients aged 13–64 years (n = 44), as in patients ≥65 years (n = 44): resting gradient pre-procedure and at last follow-up were median (IQR) 65 (71) and 12 (20) mmHg for <65 year-olds (P < 0.001), and 75 (64) and 14 (38) mmHg, respectively, for ≥65 year-olds (P < 0.001). New York Heart Association class improved significantly in both age ranges to 1.6 ± 0.6 and 1.8 ± 0.7, respectively (P < 0.001; P < 0.001).ConclusionShort AV delay pacing provided lasting satisfactory relief of symptoms and outflow obstruction in the majority of patients, with low risk of requiring reintervention. Our findings support the view that pacing therapy should be considered a valid option to treat patients with HOCM.

Mitral-Aortic Flow Reversal in Cardiac Resynchronization Therapy: Coupling With Ejection and Impact of Variations in Atrioventricular Delay.

Flow entering the left ventricle is reversed toward the outflow tract through rotating reversal flow around the mitral valve. This was thought to facilitate early ejection, but had not been proved to date. We hypothesized that perfect coupling between reversal and ejection flow would occur at optimal atrioventricular delay (AVD), contributing to its hemodynamic superiority, and evaluated its applicability for AVD optimization. Forty consecutive patients with cardiac resynchronization therapy underwent intracardiac flow analysis and AVD optimization. Reversal and ejection flow curves were studied. The presence and duration of reversal-ejection discontinuity were assessed for all programmed AVD. Reproducibility of each optimization method was evaluated through interobserver variability. Discontinuity between reversal and ejection flow was observed in all patients with longer than optimal AVD, increasing linearly with excess duration in AVD (linear R2=0.976, P<0.001). Longer discontinuities implied progressive decreases in pre-ejection flow velocity in the left ventricular outflow tract, with consequent loss of flow momentum. The equation optimal AVD=programmed AVD-[1.2(discontinuity duration)]+4 accurately predicted optimal AVD. Short AVD systematically compromised reversal flow because of premature ejection. Agreement over optimal AVD was superior when assessed by flow reversal method (intraclass correlation coefficient =0.931; P<0.001) over both iterative and aortic velocity-time integral methods. Perfect coupling between mitral-aortic flow reversal and ejection flow in the left ventricle occurs at optimal AVD. As a result, full blood momentum in the outflow tract is used to facilitate early ejection. This can be measured and provides a new method for AVD optimization.

Young Investigator Award session: Basic Science311Intraventricular flow patterns after percutaneous mitral valve repair with MitraClip implantation312Papillary muscles contribute significantly to shortening of dilated left ventricles313Relationship between cardiac uptake by 99mTc-DPD scintigraphy and left ventricular longitudinal strain in patients with transthyretin-related cardiac amyloidosis314Premature ventricular contraction in resynchronized patients with short atrio-ventricular delay: hemodynamic impact beyond A-wave truncation

Young Investigator Award session: Basic Science311Intraventricular flow patterns after percutaneous mitral valve repair with MitraClip implantation312Papillary muscles contribute significantly to shortening of dilated left ventricles313Relationship between cardiac uptake by 99mTc-DPD scintigraphy and left ventricular longitudinal strain in patients with transthyretin-related cardiac amyloidosis314Premature ventricular contraction in resynchronized patients with short atrio-ventricular delay: hemodynamic impact beyond A-wave truncation

Sequential Atrioventricular Pacing in Patients With Hypertrophic Cardiomyopathy: An 18-year Experience

Introduction and objectivesControversy persists regarding the role of sequential atrioventricular pacing in patients with obstructive hypertrophic cardiomyopathy and disabling symptoms. The aim of this study was to evaluate the effect of pacing on symptoms, dynamic gradient, and left ventricular function in patients with hypertrophic cardiomyopathy. MethodsFrom 1991 to 2009, dual-chamber pacemakers were implanted in 82 patients with obstructive hypertrophic cardiomyopathy and disabling symptoms despite optimal medical therapy. Sequential pacing was performed with a short atrioventricular delay. Clinical and echocardiographic parameters were measured before and immediately after implantation and after a long follow-up (median, 8.5 years [range, 1-18 years]). ResultsThe New York Heart Association functional class was immediately reduced after pacemaker implantation in 95% of patients (P < .0001), and this improvement was maintained until the final follow-up in 89% (P = .016). The gradient was significantly reduced after implantation (94.5 ± 36.5 vs 46.4 ± 26.7mmHg; P < .0001) and at final follow-up (94.5 ± 36.5 vs 35.9 ± 24.0mmHg; P < .0001). Mitral regurgitation permanently improved in 52% of the patients (P < .0001). There were no differences in ventricular thickness or diameters, ejection fraction, or diastolic function. ConclusionsSequential pacing in selected patients with obstructive hypertrophic cardiomyopathy improves functional class and reduces dynamic gradient and mitral regurgitation immediately after pacemaker implantation and at final follow-up. Prolonged ventricular pacing has no negative effects on systolic or diastolic function in these patients.

Estimulación auriculoventricular secuencial en pacientes con miocardiopatía hipertrófica: 18 años de experiencia

Introduction and objectivesControversy persists regarding the role of sequential atrioventricular pacing in patients with obstructive hypertrophic cardiomyopathy and disabling symptoms. The aim of this study was to evaluate the effect of pacing on symptoms, dynamic gradient, and left ventricular function in patients with hypertrophic cardiomyopathy. MethodsFrom 1991 to 2009, dual-chamber pacemakers were implanted in 82 patients with obstructive hypertrophic cardiomyopathy and disabling symptoms despite optimal medical therapy. Sequential pacing was performed with a short atrioventricular delay. Clinical and echocardiographic parameters were measured before and immediately after implantation and after a long follow-up (median, 8.5 years [range, 1-18 years]). ResultsThe New York Heart Association functional class was immediately reduced after pacemaker implantation in 95% of patients (P < .0001), and this improvement was maintained until the final follow-up in 89% (P = .016). The gradient was significantly reduced after implantation (94.5 ± 36.5 vs 46.4 ± 26.7mmHg; P < .0001) and at final follow-up (94.5 ± 36.5 vs 35.9 ± 24.0mmHg; P < .0001). Mitral regurgitation permanently improved in 52% of the patients (P < .0001). There were no differences in ventricular thickness or diameters, ejection fraction, or diastolic function. ConclusionsSequential pacing in selected patients with obstructive hypertrophic cardiomyopathy improves functional class and reduces dynamic gradient and mitral regurgitation immediately after pacemaker implantation and at final follow-up. Prolonged ventricular pacing has no negative effects on systolic or diastolic function in these patients.Full English text available from:www.revespcardiol.org/en

Applicability of the iterative technique for cardiac resynchronization therapy optimization: full-disclosure, 50-sequential-patient dataset of transmitral Doppler traces, with implications for future research design and guidelines

Full-disclosure study describing Doppler patterns during iterative atrioventricular delay (AVD) optimization of biventricular pacemakers (cardiac resynchronization therapy, CRT). Doppler traces of the first 50 eligible patients undergoing iterative Doppler AVD optimization in the BRAVO trial were examined. Three experienced observers classified conformity to guideline-described patterns. Each observer then selected the optimum AVD on two separate occasions: blinded and unblinded to AVD. Four Doppler E-A patterns occurred: A (always merged, 18% of patients), B (incrementally less fusion at short AVDs, 12%), C (full separation at short AVDs, as described by the guidelines, 28%), and D (always separated, 42%). In Groups A and D (60%), the iterative guidelines therefore cannot specify one single AVD. On the kappa scale (0 = chance alone; 1 = perfect agreement), observer agreement for the ideal AVD in Classes B and C was poor (0.32) and appeared worse in Groups A and D (0.22). Blinding caused the scattering of the AVD selected as optimal to widen (standard deviation rising from 37 to 49 ms, P < 0.001). By blinding 28% of the selected optimum AVDs were ≤60 or ≥200 ms. All 50 Doppler datasets are presented, to support future methodological testing. In most patients, the iterative method does not clearly specify one AVD. In all the patients, agreement on the ideal AVD between skilled observers viewing identical images is poor. The iterative protocol may successfully exclude some extremely unsuitable AVDs, but so might simply accepting factory default. Irreproducibility of the gold standard also prevents alternative physiological optimization methods from being validated honestly.

Goldilocks and the importance of AV intervals in cardiac resynchronization—How to best find the AV interval that is not too long, not too short, but just right for patients

Long before cardiac resynchronization (CRT) became standard therapy for patients with QRS prolongation and drug-refractory heart failure, standard dual chamber pacing in the right atrium and right ventricle using short atrioventricular (AV) delays was undertaken. The proponents of this procedure performed in patients without traditional bradycardia indications for pacing theorized that a shortened AV delay would decrease symptoms of heart failure by decreasing mitral and tricuspid valve regurgitation. Several case reports and case studies demonstrated favorable outcomes of improvement in cardiac output and decrease in symptoms of breathlessness in patients randomized to right ventricular pacing with short AV intervals. 1,2 Right ventricular pacing solely to improve symptomatic heart failure in patients without bradycardia was no longer thought useful after the publication of a double-blind randomized crossover trial of 12 patients, which demonstrated no difference in hemodynamic parameters or symptoms of heart failure between the times spent in the backup VVI 40 beats/min mode vs the VDD mode with an AV delay of 100 ms. The importance of AV intervals was realized even in the early days of left ventricular pacing for the treatment of heart failure. In a substudy of the Pacing Therapies in Congestive Heart Failure (PATH-CHF) trial, patients with a left bundle branch block treated with an epicardial left ventricular lead had significant differences in acute hemodynamic parameters as the AV interval was varied. There were significant variations in the optimal AV interval among individual patients, but the greatest benefit was seen as improvements in aortic pulse pressure, aortic systolic pressure, and left ventricular contractility if the AV interval was not too short and not too long. 3

Further Deterioration of LV Ejection Fraction and Mechanical Synchrony During RV Apical Pacing in Patients with Heart Failure and LBBB

Electrocardiographic left bundle branch block (LBBB) may be due to intrinsic disease of the left bundle branch or induced by right ventricular apical (RVA) pacing. Prior reports clearly delineate the derogatory impact of LBBB on left ventricular (LV) mechanical function but suggest equivalent impact between varieties. We hypothesized that their effects were disparate and performed a within-patient comparison to test this notion. Patients (n = 20) with heart failure, intrinsic LBBB, and an implanted pacing device with right atrial and RVA leads were studied. Each patient underwent transthoracic three-dimensional speckle-tracking echocardiography during atrial pacing (intrinsic LBBB) and short atrioventricular delay atrial-RVA pacing, and these studies were compared. Relative to intrinsic LBBB, RVA pacing-induced LBBB produced greater intra-LV and interventricular dyssynchrony, a deterioration in LV function, and a shift in the site of latest activation. In patients with heart failure and LBBB, acute RVA pacing induces greater mechanical dyssynchrony and further impairs LV function.

Influence of Atrioventricular Interaction on Mitral Valve Closure and Left Ventricular Isovolumic Contraction Measured by Tissue Doppler Imaging

The influence of atrioventricular (AV) interaction on mitral valve closure (MVC) and left ventricular (LV) isovolumic contraction is not fully clarified. We investigated the relationship among AV delay, MVC, and LV isovolumic contraction using a horse model because of the low heart rate and physiologically long AV delay. Six horses were evaluated during sinus rhythm, right ventricular pacing without preceding atrial contraction, and dual-chamber pacing at AV delays of 150 to 350 ms, programmed at a constant rate. Right parasternal 4-chamber views were recorded for simultaneous measurements of MVC from anatomic M-mode and radial tissue Doppler-based LV pre-ejection velocity and isovolumic acceleration. During sinus rhythm and long AV delays (≥300 ms), 2 positive pre-ejection velocity peaks were present. The first peak was identified as LV recoil during atrial relaxation and consistently preceded MVC by 33±17 ms. The second peak was related to LV isovolumic contraction, occurring after MVC. This suggests that MVC was caused by atrial relaxation and followed by true isovolumic contraction. During short AV delays (<300 ms) and right ventricular pacing, MVC occurred significantly later. Only 1 pre-ejection peak was present, of which the end coincided with MVC with a mean difference of -1.5±10 ms. This suggests that LV contraction caused MVC. Peak velocity and isovolumic acceleration were significantly higher (P<0.001) because the mitral valve was open at the onset of LV contraction. Depending on the AV delay, MVC can be atrio- or ventriculogenic, resulting in significant alterations of the LV peak pre-ejection velocity and isovolumic acceleration.

Medical, Surgical and Interventional Management of Hypertrophic Cardiomyopathy With Obstruction

Patients with hypertrophic cardiomyopathy (HCM) are classified as having hypertrophic obstructive cardiomyopathy (HOCM) if a left ventricular outflow tract (LVOT) gradient is present at rest or during provocation, as with Valsalva maneuver or exercise. Management of HCM in general and HOCM in particular encompasses (1) activity restriction with avoidance of volume depletion, (2) prevention of sudden cardiac death, (3) control of symptoms, and (4) screening of relatives. Those patients at high risk of sudden cardiac death (SCD) should be offered an implantable cardioverter-defibrillator (ICD). Pharmacologic treatment of symptoms in patients with HOCM consists of negative inotropic drugs, namely beta blockers, and disopyramide; a nondihydropyridine calcium channel blocker (CCB), usually verapamil, may be used in patients with noncardiac side-effects of beta blockers. Patients who have a dual-chamber pacemaker (PM) or ICD should undergo a trial of pacing with short atrioventricular (AV) delay. For patients with intolerable symptoms despite optimal conservative therapy, septal reduction therapy (SRT) should be considered and should be performed by experienced operators in institutions with multidisciplinary HCM programs. Younger patients with extreme hypertrophy are usually offered septal myectomy, while older patients, and those with important comorbidities are usually directed to alcohol septal ablation (ASA). For patients for whom either therapy is appropriate, there should be a balanced discussion with the patients of the benefits and risks of the 2 procedures.

Management Strategy in 249 Consecutive Patients With Obstructive Hypertrophic Cardiomyopathy Referred to a Dedicated Program

The likelihood of success of conservative management of obstructive hypertrophic cardiomyopathy (HC) and the predictors of failure of conservative therapy are not known. We therefore evaluated the efficacy of an algorithm for the management of symptoms and predictors of failed conservative therapy in 249 consecutive symptomatic patients with obstructive HC referred to a dedicated HC program for management in general or for septal reduction therapy (SRT) in particular. There was considerable practice variation in the extent to which conservative therapy was optimized before referral for SRT. Over 3.7 ± 2.9-year follow-up, symptoms resolved with addition of or increase in dosage of a β blocker, calcium channel blocker, or disopyramide in 16%, 10%, and 10% of patients, respectively. Pacing with short atrioventricular delay controlled symptoms in 4 of 9 patients. In 63% of patients, conservative measures failed to control symptoms. Multivariate predictors of failure of conservative therapy were presence of New York Heart Association class III or IV symptoms (hazard ratio 2.0, 95% confidence interval 1.4 to 2.9, p = 0.001) and greater septal wall thickness (hazard ratio 1.06, 95% confidence interval 1.02 to 1.10, p = 0.003) at presentation. At time of presentation, 93 patients (37%) were already on optimal therapy and were referred for SRT. Of the remaining 156 patients who did not require immediate SRT, 93 (60%) were free from a recommendation for SRT at the end of the follow-up period. In conclusion, in symptomatic patients with obstructive HC, conservative therapy is successful in >1/3 of referred patients at 3.7-year follow-up, obviating SRT in these patients. Clinicians in programs offering SRT should optimize conservative therapy before recommending SRT.

Vectorcardiography as a Tool for Easy Optimization of Cardiac Resynchronization Therapy in Canine Left Bundle Branch Block Hearts

Background— In cardiac resynchronization therapy (CRT), optimization of left ventricular (LV) stimulation timing is often time consuming. We hypothesized that the QRS vector in the vectorcardiogram (VCG) reflects electric interventricular dyssynchrony, and that the QRS vector amplitude (VA QRS ), halfway between that during left bundle branch block (LBBB) and LV pacing, reflects optimal resynchronization, and can be used for easy optimization of CRT. Methods and Results— In 24 canine hearts with LBBB (12 acute, 6 with heart failure, and 6 with myocardial infarction), the LV was paced over a wide range of atrioventricular (AV) delays. Surface ECGs were recorded from the limb leads, and VA QRS was calculated in the frontal plane. Mechanical interventricular dyssynchrony (MIVD) was determined as the time delay between upslopes of LV and right ventricular pressure curves, and systolic function was assessed as LV dP/dt max . VA QRS and MIVD were highly correlated ( r =0.94). The VA QRS halfway between that during LV pacing with short AV delay and intrinsic LBBB activation accurately predicted the optimal AV delay for LV pacing (1 ms; 95% CI, –5 to 8ms). Increase in LV dP/dt max at the VCG predicted AV delay was only slightly lower than the highest observed ∆LV dP/dt max (–2.7%; 95% CI, –3.6 to –1.8%). Inability to reach the halfway value of VA QRS during simultaneous biventricular pacing (53% of cases) was associated with suboptimal hemodynamic response, which could be corrected by sequential pacing. Conclusions— The VA QRS reflects electric interventricular dyssynchrony and accurately predicts optimal timing of LV stimulation in canine LBBB hearts. Therefore, VCG may be useful as a reliable and easy tool for individual optimization of CRT.

AAIR or DDDR pacing for sick sinus syndrome: the physiologic conundrum

The results of the DANPACE multicentre trial were recently published.1 There were 1415 patients with symptomatic sick sinus syndrome (SSS) and normal QRS width, randomly assigned to single-chamber AAIR pacing (707 patients) or dual-chamber DDDR pacing with a tailored atrio-ventricular (AV) delay, designed to prevent ventricular pacing (708 patients). During a mean follow-up period of 5.4 ± 2.6 years, paroxysmal atrial fibrillation (AF) was observed in 28.4% in the AAIR group vs. 23% in the DDDR group ( P < 0.024). There were significantly more deaths ( P = 0.024) and pacemaker reoperations ( P < 0.001) in the single-chamber group, whereas there was no difference with chronic AF, stroke, and hospitalization for heart failure. Despite AV-delay tailoring, ventricular pacing in the DDDR group was 65% with a mean AV delay of 225 ± 39 ms. These data are in contrast to the original Danish trial published in 2003 with the lead author being involved with both trials.2 This smaller study of 177 patients had three groups randomized to AAIR, DDDR with short AV delay (DDDR-s), and DDDR with fixed long AV delay (DDDR-l). During a mean follow-up period of 2.9 ± 1.1 years, AF, both paroxysmal and chronic, was significantly less common in the AAIR group. Long-term DDDR pacing also induced left atrial dilatation, and in the DDDR-s group (90% ventricular pacing) there was also reduced left ventricular function. Seeing the results are so different how does this compare with other studies? In 2003, Sweeney et al .3 reported a …