Long‐Term Mechanical Consequences of Permanent Right Ventricular Pacing: Effect of Pacing Site

Optimal Right Ventricular Pacing Introduction: Long‐term right ventricular apical (RVA) pacing has been associated with adverse effects on left ventricular systolic function; however, the comparative effects of right ventricular outflow tract (RVOT) pacing are unknown. Our aim was therefore to examine the long‐term effects of septal RVOT versus RVA pacing on left ventricular and atrial structure and function. Methods: Fifty‐eight patients who were prospectively randomized to long‐term pacing either from the right ventricular apex or RVOT septum were studied echocardiographically. Left ventricular (LV) and atrial (LA) volumes were measured. LV 2D strain and tissue velocity images were analyzed to measure 18‐segment time‐to‐peak longitudinal systolic strain and 12‐segment time‐to‐peak systolic tissue velocity. Intra‐LV synchrony was assessed by their respective standard deviations. Interventricular mechanical delay was measured as the difference in time‐to‐onset of systolic flow in the RVOT and LV outflow tract. Septal A’ was measured using tissue velocity images. Results: Following 29 ± 10 months pacing, there was a significant difference in LV ejection fraction (P < 0.001), LV end‐systolic volume (P = 0.007), and LA volume (P = 0.02) favoring the RVOT‐paced group over the RVA‐paced patients. RVA‐pacing was associated with greater interventricular mechanical dyssynchrony and intra‐LV dyssynchrony than RVOT‐pacing. Septal A’ was adversely affected by intra‐LV dyssynchrony (P < 0.05). Conclusions: Long‐term RVOT‐pacing was associated with superior indices of LV structure and function compared with RVA‐pacing, and was associated with less adverse LA remodeling. If pacing cannot be avoided, the RVOT septum may be the preferred site for right ventricular pacing. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1120‐1126)     

Acute pacing-induced dyssynchronous activation of the left ventricle creates systolic dyssynchrony with preserved diastolic synchrony

Introduction: Patients with heart block have conventionally received a pacemaker that stimulates the right ventricular apex (RVA) to restore heart rate control. While RVA pacing has been shown to create systolic dyssynchrony acutely, dyssynchrony can also occur in diastole. The effects of acute RVA pacing on diastolic synchrony have not been investigated. RVA pacing acutely impairs diastolic function by increasing the time constant of relaxation, decreasing the peak lengthening rate and decreasing peak negative dP/dt. We therefore hypothesized that acute RVA pacing would cause diastolic dyssynchrony in addition to creating systolic dyssynchrony.
Methods and Results: Fourteen patients (13 ± 4 years old) with non-preexcited supraventricular tachycardia underwent ablation therapy with subsequent testing to confirm elimination of the tachycardia substrate. Normal cardiac structure and function were then documented on two-dimensional echocardiography and 12-lead electrocardiography prior to enrollment. Tissue Doppler images were collected during normal sinus rhythm (NSR), right atrial appendage pacing (AAI), and VVI-RVA pacing during the postablation waiting interval. Systolic and diastolic dyssynchrony were quantified using cross-correlation analysis of tissue Doppler velocity curves. Systolic dyssynchrony increased 81% during RVA pacing relative to AAI and NSR (P < 0.01). Diastolic synchrony was not affected by the different pacing modes (P = 0.375).
Conclusion: Acute dyssynchronous activation of the LV created by RVA pacing resulted in systolic dyssynchrony with preserved diastolic synchrony in pediatric patients following catheter ablation for treatment of supraventricular tachycardia. Our results suggest that systolic and diastolic dyssynchrony are not tightly coupled and may develop through separate mechanisms.     

Tissue Doppler imaging a new prognosticator for cardiovascular diseases

Tissue Doppler imaging (TDI) is evolving as a useful echocardiographic tool for quantitative assessment of left ventricular (LV) systolic and diastolic function. Recent studies have explored the prognostic role of TDI-derived parameters in major cardiac diseases, such as heart failure, acute myocardial infarction, and hypertension. In these conditions, myocardial mitral annular or basal segmental (Sm) systolic and early diastolic (Ea or Em) velocities have been shown to predict mortality or cardiovascular events. In particular, those with reduced Sm or Em values of <3 cm/s have a very poor prognosis. In heart failure and after myocardial infarction, noninvasive assessment of LV diastolic pressure by transmitral to mitral annular early diastolic velocity ratio (E/Ea or E/Em) is a strong prognosticator, especially when E/Ea is > or =15. In addition, systolic intraventricular dyssynchrony measured by segmental analysis of myocardial velocities is another independent predictor of adverse clinical outcome in heart failure subjects, even when the QRS duration is normal. In heart failure patients who received cardiac resynchronization therapy, the presence of systolic dyssynchrony at baseline is associated with favorable LV remodeling, which in turn predicts a favorable long-term clinical outcome. Finally, TDI and derived deformation parameters improve prognostic assessment during dobutamine stress echocardiography. A high mean Sm value in the basal segments of patients with suspected coronary artery disease is associated with lower mortality rate or myocardial infarction and is superior to the wall motion score.     

Tissue Doppler imaging a new prognosticator for cardiovascular diseases.

Tissue Doppler imaging (TDI) is evolving as a useful echocardiographic tool for quantitative assessment of left ventricular (LV) systolic and diastolic function. Recent studies have explored the prognostic role of TDI-derived parameters in major cardiac diseases, such as heart failure, acute myocardial infarction, and hypertension. In these conditions, myocardial mitral annular or basal segmental (Sm) systolic and early diastolic (Ea or Em) velocities have been shown to predict mortality or cardiovascular events. In particular, those with reduced Sm or Em values of <3 cm/s have a very poor prognosis. In heart failure and after myocardial infarction, noninvasive assessment of LV diastolic pressure by transmitral to mitral annular early diastolic velocity ratio (E/Ea or E/Em) is a strong prognosticator, especially when E/Ea is > or =15. In addition, systolic intraventricular dyssynchrony measured by segmental analysis of myocardial velocities is another independent predictor of adverse clinical outcome in heart failure subjects, even when the QRS duration is normal. In heart failure patients who received cardiac resynchronization therapy, the presence of systolic dyssynchrony at baseline is associated with favorable LV remodeling, which in turn predicts a favorable long-term clinical outcome. Finally, TDI and derived deformation parameters improve prognostic assessment during dobutamine stress echocardiography. A high mean Sm value in the basal segments of patients with suspected coronary artery disease is associated with lower mortality rate or myocardial infarction and is superior to the wall motion score.     

Acute Effects of Withdrawal of Cardiac Resynchronization Therapy on Left and Right Ventricular Function,Dyssynchrony, and Contractile Function in Patients With New York Heart Association Functional Class I/II Heart Failure: MADIT-CRT

BackgroundCardiac resynchronization therapy (CRT) improves left ventricular (LV) function, size, mitral regurgitation, and clinical outcomes. Whether these improvements are due to the short-term effects of improvement in synchrony or contractile performance, or to long-term improvement in ventricular structure and function remains insufficiently elucidated.Methods and ResultsWe used echocardiographic data from 63 patients enrolled in the MADIT-CRT trial who, after 1 year of CRT therapy, underwent echocardiographic evaluation with CRT turned both on and off within minutes. LV volumes, LV ejection fraction, left atrial (LA) volumes, and right ventricular function were assessed at baseline and in the on and off modes within a 5-minute time-frame at 12 months. Speckle-tracking strain analysis was used to assess LV dyssynchrony and contractile function. Interruption of long-term CRT resulted in acute deterioration of LV and RV function and acute increase in LV and LA volumes, although not to baseline. Acute withdrawal was also associated with increased dyssynchrony (SD time to peak transverse strain 178 ± 68 ms vs 195 ± 62 ms; P = .16; and SD time to peak longitudinal strain 108 ± 46 ms vs 125 ± 55 ms; P = .046). However, there was no deterioration in contractile function (global longitudinal strain), which had improved with CRT (?9.8 ± 4.3% vs ?10.0 ± 3.7%; P = .93).ConclusionsDespite substantial LV reverse remodeling with CRT, interruption of long-term CRT after 12 months resulted in an acute worsening of LV size and function, LA volumes, and right ventricular function, with concomitant worsening of ventricular synchrony despite minimal change to the observed improvement in LV strain measures of contractile function. These findings suggest that the beneficial reverse remodeling associated with CRT may be mostly dependent on active pacing, although intrinsic improvements in contractile function may persist beyond termination of pacing.     

Supernormal diastolic function and role of left atrial myocardial deformation analysis by 2D speckle tracking echocardiography in elite soccer players

Purpose: Top‐level training is associated with morphological and functional changes in the heart. Left atrial (LA) enlargement can be regarded as a physiologic adaptation to exercise conditioning. Athletes show an improvement in myocardial diastolic properties and supernormal left ventricular (LV) diastolic function. The aims of the study were to assess diastolic function by pulsed Doppler tissue imaging (DTI) and to analyze the role of LA in athletes by speckle tracking echocardiography (STE). Methods: Twenty‐three male elite soccer players underwent a complete echocardiographic analysis. Twenty‐six age‐matched healthy sedentary men were used as controls. Measured variables included LA indexed volumes, DTI of the LV, peak atrial longitudinal strain, and peak atrial contraction strain (PACS). Results: LA areas and indexed volumes were significantly higher in athletes (P < 0.001). Athletes had a higher peak E velocity (P < 0.001), a lower A peak (P < 0.01), and a higher peak E/A ratio (P < 0.0001); a higher Em peak (P < 0.001), a lower Am peak (P < 0.01), and a higher Em/Am ratio (P < 0.0001). Global PACS was lower in athletes compared with controls (P < 0.0001) and strongly correlated with mitral Am (r = 0.55; P < 0.0001), mitral Em (r =?0.41; P < 0.001), heart rate (r =?0.38; P < 0.01), and LA area (r = 0.18; P < 0.05). Conclusions: Athletes showed a shift in the pattern of ventricular filling period toward early diastole as seen through DTI analysis of the diastolic properties of LV and STE analysis of LA function. DTI is a useful tool to analyze the improved myocardial diastolic properties of athletes and STE may elucidate the role of LA in the context of athlete's heart remodeling. (Echocardiography 2011;28:320‐326)     

Provocation of masked left ventricular mechanical dyssynchrony by treadmill exercise in patients with systolic heart failure and narrow QRS complex

Tissue Doppler imaging-derived intra-left ventricular (LV) contractile dyssynchrony is an evolving prognostic parameter for patients with systolic heart failure (HF). However, whether and how exercise could abolish the synchronicity in HF patients with narrow QRS remains less studied. We evaluated a total of 33 HF patients with impaired LV ejection fraction (<50%), QRS duration < or =120 ms, and baseline dyssynchrony index (DI; standard deviation of electromechanical delay of 12 LV segments by tissue Doppler imaging) <33 ms. After a 6-minute treadmill exercise by modified Bruce protocol, the absolute time difference from QRS onset to peak systolic myocardial velocity of each segment was recorded immediately. With similar DI at rest and peak heart rates during exercise, 11 patients (33%) developed dyssynchrony (DI > or =33 ms) after exercise, and the others did not (44.7 +/- 8.0 vs 16.2 +/- 8.3 ms, p <0.001). Patients with dyssynchrony after exercise had greater baseline mitral early diastolic velocity/annular early diastolic velocity (E/Ea) (19 +/- 17 vs 10 +/- 5, p <0.026). Multivariate analysis revealed mitral E/Ea >10 at rest, indicating higher LV filling pressure, independently predicted the exercise-evoked dyssynchrony (odds ratio 18, 95% confidence interval 2 to 163, p <0.012). In conclusion, exercise uncovered masked LV dyssynchrony in 1/3 of systolic HF patients with narrow QRS, and exercise-provoked dyssynchrony could be predicted by mitral E/Ea >10 at rest.     

Reduced Atrial Emptying after Orthotopic Heart Transplantation Masquerading as Restrictive Transmitral Doppler Flow Pattern?*

Background: An elevated early (E) to late (A) diastolic filling velocities ratio, typically seen in advanced diastolic dysfunction, has also been observed after cardioversion of atrial fibrillation as a consequence of the depressed left atrial (LA) contractility. We hypothesized that the impaired LA contractile function demonstrated after orthotopic cardiac transplantation (OCT) could also lead to this “pseudorestrictive” pattern. Method: E/A ratio related to the tissue Doppler early mitral annular velocity (Ea) as preload‐independent index of LV relaxation was evaluated in all consecutive OCT patients between 2005 and 2007. Results: The study population comprised 48 patients 97 ± 77 months after OCT. Thirty‐two patients (67%) had an E/A ratio > 2. LV systolic function and myocardial relaxation assessed by the Ea velocity were similar compared to patients with normal ratio (61 ± 6% vs. 60 ± 12%, P = 0.854 and 15 ± 4 cm/s vs. 14 ± 3 cm/s, r = 0.15, P = 0.323, respectively). On the other hand, the proportion of the recipient and donor LA cuffs as estimated by the recipient/global LA area ratio and the LA emptying fraction significantly correlated with the E/A ratio (r = 0.40, P = 0.005 and r =?0.33, P = 0.022, respectively). Conclusion: Our study shows that there is a high prevalence of elevated E/A ratio after standard OCT which seems mainly related to reduced LA contractility. Recognition of this “pseudorestrictive” pattern may avoid misdiagnosis of diastolic dysfunction. (Echocardiography 2011;28:168‐174)     

Acute mechanical effect of right ventricular pacing at different sites using velocity vector imaging

Objective: Velocity vector imaging (VVI) allows noninvasive measurement of left ventricular (LV) strain and rotation angle‐independently. We investigated strain, rotation and myocardial synchrony when pacing at different sites in the right ventricle to determine which site yields the most physiological pacing, as determined with VVI imaging. Method: Thirty‐one patients with normal LV function referred for elective electrophysiology exam were used in this study. Catheters (6F quadripolar) were positioned in the right atrium, right ventricular apex, right ventricular outflow tract, and His bundle after electrophysiology exam was done. Regional and global LV circumferential strain (CS), radial strain (RS), and LV rotation of LV short‐axis measurements were obtained. Two dyssynchrony parameters (AS‐P delay and SDt_6S) of CS and RS were obtained. Compare these values among each pacing, respectively. Result: CS, RS, and twist, which represent the LV systolic function, were significantly reduced in RVOT pacing and RVA pacing than RA pacing. Two dyssynchrony parameters (AS‐P delay and SDt_6S) were significantly longer in response to RVOT or RVA pacing compared to RA pacing. No significant differences were found between RVOT pacing and RVA pacing. CS and RS were obviously reduced in the regions surrounding the pacing site. There was no significant difference in CS, RS, twist, and mechanical dyssynchrony parameters when comparing His and RA pacing. Conclusion: Among these alternate right ventricular pacing locations, His bundle pacing is most like physiological pacing. Both RVOT pacing and RVA pacing worsen the normal LV systolic function with regard to strain, twist, and mechanical dyssynchrony along the LV short axis. (Echocardiography 2010;27:1219‐1227)     

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.     

The impact of hypertension and hypertension-related left ventricle hypertrophy on right ventricle function

AIM: The aim of our study is to determine the effect of hypertension and hypertension-related left ventricle hypertrophy on right ventricle (RV) morphology and function by using RV standard Doppler echocardiographic indices, myocardial Doppler imaging, and strain/strain rate imaging indices. METHODS: We studied 35 patients with arterial hypertension and 30 age- and sex-adjusted control subjects who had no other pathological conditions. Standard transthoracic Doppler echocardiographical measurements, pulsed-wave tissue Doppler from tricuspid anulus (Peak systolic-st, peak early diastolic-et, peak late diastolic velocity-at), reconstructed spectral pulsed-wave tissue Doppler velocities (peak systolic-S, peak early-E, peak late diastolic velocity-A), and strain/strain rate imaging of RV free wall mid region (peak systolic strain-in, peak systolic strain rate-SR) were obtained. RESULTS: Age, body surface area, blood pressure, and heart rate were comparable between two groups. Hypertensive subjects had significantly increased LV end-diastolic septal and posterior wall thickness, left atrial diameter, LV mass, LV mass index, and relative wall thickness during diastole. At the level of right ventricular lateral tricuspid annulus without systolic changes, the majority of diastolic measurements were altered in hypertensives (early diastolic velocity et; 13 +/- 2 vs. 18 +/- 4 m/sec, P < 0.0001, late diastolic velocity at; 20 +/- 4 vs. 14 +/- 3 m/sec, P < 0.0001, early to late diastolic velocity ratio; 0.69 +/- 0.14 vs. 1.32 +/- 0.38, P < 0.0001). The velocity data from two-dimensional color myocardial imaging at the level of RV free wall mid region again showed altered diastolic measurements in hypertensives (E; 8.01 +/- 2.6 vs. 10.4 +/- 3.14 m/sec, P < 0.001, A; 11.5 +/- 2.6 vs. 9.12 +/- 3.7 m/sec, P < 0.0001, E/A ratio; 0.75 +/- 0.41 vs. 1.87 +/- 0.48, P < 0.00). The peak systolic strain of RV free wall mid region was significantly lower in hypertensive individuals than controls (25.666 +/- 5.64 vs. 30.03 +/- 6.78%, P < 0.05). No significant differences were found in other parameters of RV function between hypertensive and control subjects. CONCLUSIONS: The present study demonstrates that besides the manifest morphologic LV adaptations, significant RV functional alterations can be determined by TDI and strain/strain rate imaging in patients arterial hypertension. Both tissue velocities by TDI and strain imaging may be new tools to define and quantitate subtle change in systolic and diastolic function of right ventricular function in arterial hypertension that cannot be determined in standard echocardiographic parameters.     

Hemodynamic improvement by right ventricular septal pacing in elderly patients with chronic atrial fibrillation and slow ventricular response

Background and objectives Right ventricular apical (RVA) pacing has been reported impairing left ventricular (LV) performance. Alternative pacing sites in right ventricle (RV) has been explored to obtain better cardiac function. Our study was designed to compare the hemodynamic effects of right ventricular septal (RVS) pacing with RVA pacing. Methods Ten elderly patients with chronic atrial fibrillation (AF) and long RR interval or slow ventricular response (VR) received VVI pacing. The hemodynamic difference between RVS and RVA pacing were examined by transthoracic echocardiography (TTE). Results Pacing leads were implanted successfully at the RVA and then RVS in all patients without complication. The left ventricular (LV) parameters, measured during RVA pacing including left ventricular ejection fraction (LVEF), FS, stroke volume (SV) and peak E wave velocity (EV) were decreased significantly compared to baseline data, while during RVS pacing, they were significantly better than those during RVA pacing. However, after 3-6 weeks there was no statistical significant difference between pre- and post- RVS pacing. Conclusions The LV hemodynamic parameters during RVA pacing were significantly worse than baseline data. The short term LV hemodynamic parameters of RVS pacing were significantly better than those of RVA pacing; RVS pacing could improve the hemodynamic effect through maintaining normal ventricular activation sequence and biventricular contraction synchrony in patients with chronic AF and slow ventricular response.(J Geriatr Cardiol 2005,2(2): 103-106).     

Cardiac resynchronization therapy in acute pulmonary edema: A case report

We are reporting a case of 71-year old lady with a dual chamber demand pacemaker,who developed acute pulmonary edema due to an acute left ventricular(LV)dysfunction and worsening in mitral valve regurgitation after atrioventricular nodal ablation for uncontrolled atrial fibrillation.This was attributed to right ventricular apical pacing leading to LV dyssynchronization.Patient dramatically improved within 12-24 h after upgrading her single chamber pacemaker to biventricular pacing.Our case demonstrates that biventricular pacing can be an effective modality of treatment of acute congestive heart failure.In particular,it can be used when it is secondary to LV dysfunction and severe mitral regurgitation attributed to significant dyssynchrony created by right ventricular pacing in patients with atrioventricular nodal ablation for chronic atrial fibrillation.     

Chronic Effect of Right Ventricular Pacing on Left Ventricular Rotational Synchrony in Patients with Complete Atrioventricular Block

Background: Chronic effect of right ventricular (RV) pacing on left ventricular (LV) rotational synchrony is unknown. The aim of this study is to assess chronic effect of RV pacing on LV rotational synchrony using two‐dimensional ultrasound speckle tracking imaging. Methods and Results: Thirty‐one patients who underwent dual‐chamber pacemaker implantation for complete atrioventricular block, and age‐ and sex‐matched 10 healthy controls were assessed. We divided our patients into RV apical (RVA, n = 16) and RV outflow tract (RVOT, n = 15) pacing groups. We compared echocardiographic parameters such as LV rotational synchrony between pacing groups and healthy control. We defined Q to peak rotation interval as the interval from the beginning of the Q‐wave to the peak apical counter‐clockwise or peak basal clockwise rotation. We calculated apical–basal rotation delay by subtracting basal Q to peak rotation interval from apical one as the representative of rotational synchronization. Apical–basal rotation delay of RVA pacing was significantly longer than that of healthy control (100 ± 110 vs. ?6 ± 15 ms, P = 0.002), while there was no statistically significant difference between RVOT pacing and healthy control (?3 ± 99 vs. ?6 ± 15 ms, P = 0.919). Conclusions: LV rotation during RVOT pacing is synchronous at 15 months after pacemaker implantation, while RVA pacing provokes LV rotational dyssynchrony by inducing delayed apical rotation at 7 years after pacemaker implantation in patients with complete atrioventricular block. (Echocardiography 2011;28:69‐75)     

Effect of acute changes in load on left ventricular diastolic function during device closure of atrial septal defects

Echocardiographic indexes of left ventricular (LV) diastolic function were assessed in 18 patients before and after device closure of secundum atrial septal defects. The tissue Doppler early diastolic peak annular velocity (Ea) and color M-mode velocity of propagation (Vp), indexes of relaxation, seemed to be load independent and were not affected by the change in LV filling hemodynamics, whereas the mitral inflow peak E-wave velocity and E/Ea ratio were more load dependent, with a resultant increase after the closure of large atrial shunts.     

Diastolic mitral annular velocity during the development of heart failure

OBJECTIVES: We sought to investigate the mechanism of reduced diastolic mitral annular velocity with diastolic dysfunction, despite elevated left atrial (LA) pressure. BACKGROUND: The peak rate of left ventricular (LV) early diastolic filling (E) and velocity of the mitral annulus due to long-axis lengthening (E(M)) are reduced in mild diastolic dysfunction. With more severe dysfunction, E increases in response to increased LA pressures. In contrast, E(M) decreases, despite increased LA pressure. METHODS: We studied eight dogs instrumented to measure LA pressure, LV pressure, and internal dimensions during the progressive development of heart failure (HF) produced by rapid pacing. RESULTS: Early diastolic filling decreased after four days of pacing from 114 +/- 32 to 88 +/- 22 ml/s (p < 0.05), but with more severe HF, it progressively increased to 155 +/- 32 ml/s (p < 0.05). In contrast, E(M) progressively decreased from 44 +/- 12 mm/s during the control period to 24 +/- 8 mm/s after four weeks (p < 0.05). Although E(M) was related to the time constant of LV relaxation (tau) (R(2) = 0.85), E was not. The latter occurred coincident with termination of the early diastolic LA to LV pressure gradient during all conditions. In contrast, with increasing HF, E(M) was progressively delayed after LA to LV pressure crossover by 37 +/- 12 ms (p < 0.05). The time from E to E(M) was related to tau (R(2) = 0.97). CONCLUSIONS: With slowed relaxation during the development of HF, E(M) is reduced and delayed so that it occurs after early, rapid filling. Thus, with slowed relaxation, E(M) does not respond to the early diastolic LA to LV pressure gradient, because it occurs when LV pressure is greater than or equal to LA pressure.     

Acute Effects of Single‐site Pacing from the Left and Right Ventricle on Ventricular Function and Ventricular–Ventricular Interactions in Children with Normal Hearts

Objective. We studied, as a physiological benchmark, acute effects of right ventricular (RV) apical, RV outflow, and left ventricular (LV) pacing in children with normal cardiac function on LV and RV function and ventricular–ventricular interactions. Design. The design of the study was a prospective, acute intervention. Setting. The study was conducted in a tertiary care electrophysiology laboratory. Population and Methods. Seven children (mean ± SD, 12 ± 4 years) were paced after accessory pathway ablation, at baseline (AOO), and with atrioventricular pacing (DOO) from the RV apex, RV outflow, and left ventricle. Outcome Measures. Right ventricular dP/dT_max and RV dP/dT_neg (high‐fidelity transducer‐tipped catheters, Millar Instruments, Houston, TX, USA), cardiac index (Fick), blood pressure, and QRS duration were measured at each pacing condition. Intra‐ and interventricular mechanical dyssynchrony, systolic‐ and diastolic peak tissue velocities, and isovolumic acceleration were recorded by tissue Doppler imaging at the lateral mitral, septal, and tricuspid annuli at each condition. Results at each pacing condition were compared by repeated‐measures analysis of variance. Results. Pacing prolonged QRS duration, causing electrical dyssynchrony (86 ± 19 ms [baseline], 141 ± 44 ms [RV apex], 121 ± 18 ms [RV outflow], and 136 ± 34 ms [LV], P < .01). Right ventricular outflow pacing caused LV intraventricular delay (63 ± 52 vs. 12 ± 7 ms, P < .05). Right ventricular apical pacing caused interventricular delay (61 ± 29 vs. 25 ± 18 ms, P < .05). There were no significant changes in blood pressure, cardiac index, RV dp/dT_max, RV dP/dT_neg, regional tissue velocities, or isovolumic acceleration during any of the pacing conditions, indicating preserved ventricular function and hemodynamics. No important ventricular–ventricular interactions were seen. Conclusions. In children with normal cardiac anatomy and function, single‐site RV apical, RV outflow, and LV pacing induce electromechanical dyssynchrony without significantly changing ventricular function or hemodynamics, or adversely affecting ventricular–ventricular interactions.     

The Role of Speckle Tracking Strain Imaging in Cardiac Pacing

In recent years, concerns have been raised about possible harmful effects of long-term right ventricular (RV) apical pacing. These detrimental effects may be related to changes in left ventricular (LV) mechanics during RV apical pacing. As a consequence, alternative RV pacing sites have been proposed, and in selected patients an upgrade from RV to biventricular pacing may be considered. Novel two-dimensional (2D) speckle tracking strain imaging allows detailed evaluation of LV mechanics, including LV mechanical dyssynchrony, LV strain and LV torsion. In this review, the role of speckle tracking strain imaging in the evaluation of LV function in patients with RV apical pacing will be reviewed. The effects of RV apical pacing on LV mechanical dyssynchrony, LV strain and LV torsion will be discussed. In addition, the role of speckle tracking strain imaging in the selection of the optimal (alternative) RV pacing site and in the selection of patients who may benefit from an upgrade from RV apical pacing to biventricular pacing will be reviewed.     

Right ventricular outflow versus apical pacing in pacemaker patients with congestive heart failure and atrial fibrillation

INTRODUCTION: Prior studies suggest that right ventricular apical (RVA) pacing has deleterious effects. Whether the right ventricular outflow tract (RVOT) is a more optimal site for permanent pacing in patients with congestive heart failure (CHF) has not been established. METHODS AND RESULTS: We conducted a randomized, cross-over trial to determine whether quality of life (QOL) is better after 3 months of RVOT than RVA pacing in 103 pacemaker recipients with CHF, left ventricular (LV) systolic dysfunction (LV ejection fraction < or = 40%), and chronic atrial fibrillation (AF). An additional aim was to compare dual-site (RVOT + RVA, 31-ms delay) with single-site RVA and RVOT pacing. QRS duration was shorter during RVOT (167 +/- 45 ms) and dual-site (149 +/- 19 ms) than RVA pacing (180 +/- 58 ms, P < 0.0001). At 6 months, the RVOT group had higher (P = 0.01) role-emotional QOL subscale scores than the RVA group. At 9 months, there were no significant differences in QOL scores between RVOT and RVA groups. Comparing RVOT to RVA pacing within the same patient, mental health subscale scores were better (P = 0.03) during RVOT pacing. After 9 months of follow-up, LVEF was higher (P = 0.04) in those assigned to RVA rather than RVOT pacing between months 6 and 9. After 3 months of dual-site RV pacing, physical functioning was worse (P = 0.04) than during RVA pacing, mental health was worse (P = 0.02) than during RVOT pacing, and New York Heart Association (NYHA) functional class was slightly better (P = 0.03) than during RVOT pacing. There were no other significant differences between RVA, RVOT and dual-site RV pacing in QOL scores, NYHA class, distance walked in 6 minutes, LV ejection fraction, or mitral regurgitation. CONCLUSION: In patients with CHF, LV dysfunction, and chronic AF, RVOT and dual-site RV pacing shorten QRS duration but after 3 months do not consistently improve QOL or other clinical outcomes compared with RVA pacing.     

Impact of aortic valve stenosis on left atrial phasic function

The aim of this study was to determine the impact of aortic stenosis (AS) on the different components of left atrial (LA) function. The study consisted of a total of 52 consecutive patients with severe AS (aortic valve area < 1 cm(2)) and 20 normal subjects matched for gender, heart rate, body surface area, and baseline systolic blood pressure. Phasic LA longitudinal function was assessed using tissue Doppler imaging. LA peak systolic (reservoir function), early diastolic (conduit function), and late diastolic (active function) strain rates were measured. During late diastole, LA peak strain (active function) was also measured. Mitral annular systolic, early diastolic (Ea), and late diastolic (Aa) velocities were also measured. Compared with controls, all strain values were significantly reduced in patients with AS. By multivariate regression analysis, mitral E-wave deceleration time (p = 0.033) and E/Ea ratio (p = 0.02, R(2) = 0.43) emerged as independently associated with LA peak systolic strain rate. Ea was the sole determinant of LA early diastolic strain rate (p < 0.0001, R(2) = 0.42), whereas LA late diastolic strain rate was independently related to aortic valve area (p = 0.031) and Aa (p = 0.022, R(2) = 0.51). In conclusion, in patients with severe AS, the 3 components of LA function are reduced. LA reservoir dysfunction is related to left ventricular filling pressures, whereas LA conduit dysfunction depends on left ventricular relaxation. Active LA dysfunction is related to the severity of AS and late left ventricular diastolic function.