Does RV Lead Positioning Provide Additional Benefit to Cardiac Resynchronization Therapy in Patients with Advanced Heart Failure?

BACKGROUND AND OBJECTIVES: The left ventricular (LV) stimulation site is currently recommended to position the lead at the lateral wall. However, little is known as to whether right ventricular (RV) lead positioning is also important for cardiac resynchronization therapy. This study compared the acute hemodynamic response to biventricular pacing (BiV) at two different RV stimulation sites: RV high septum (RVHS) and RV apex (RVA). METHODS AND RESULTS: Using micro-manometer-tipped catheter, LV pressure was measured during BiV pacing at RV (RVA or RVHS) and LV free wall in 33 patients. Changes in LV dP/dt(max) and dP/dt(min) from baseline were compared between RVA and RVHS. BiV pacing increased dP/dt(max) by 30.3 +/- 1.2% in RVHS and by 33.3 +/- 1.7% in RVA (P = n.s.), and decreased dP/dt(min) by 11.4 +/- 0.7% in RVHS and by 13.0 +/- 1.0% in RVA (P = n.s.). To explore the optimal combination of RV and LV stimulation sites, we assessed separately the role of RV positioning with LV pacing at anterolateral (AL), lateral (LAT), or posterolateral (PL) segment. When the LV was paced at AL or LAT, the increase in dP/dt(max) with RVHS pacing was smaller than that with RVA pacing (AL: 12.2 +/- 2.2% vs 19.3 +/- 2.1%, P < 0.05; LAT: 22.0 +/- 2.7% vs 28.5 +/- 2.2%, P < 0.05). There was no difference in dP/dt(min) between RVHS- and RVA pacing in individual LV segments. CONCLUSIONS: RVHS stimulation has no overall advantage as an alternative stimulation site for RVA during BiV pacing. RVHS was equivalent with RVA in combination with the PL LV site, while RVA was superior to RVHS in combination with AL or LAT LV site.     

Optimal sensed atrio-ventricular interval determined by paced QRS morphology

BACKGROUND: In cardiac resynchronization therapy (CRT), the atrio-ventricular (AV) and interventricular (VV) intervals have to be optimized. For maximal optimization, the paced and sensed AV intervals have to be determined. We hypothesized that the morphology of the paced QRS complex at the optimal paced AV interval (PAV) can be used to determine the optimal sensed AV (SAV) interval in patients with normal AV conduction. PATIENTS AND METHODS: In 16 patients with implanted CRT devices, the optimal PAV and V-V interval were determined by invasive measurement of left ventricle (LV) dP/dt(max). A 12-lead electrocardiogram (ECG) was recorded at the optimum setting. Subsequently, during atrial sensing ventricular pacing, the SAV interval was changed until the QRS morphology was identical to the morphology at the optimal PAV interval. The optimal SAV interval was verified by repeated measurement of LV dP/dt(max). RESULTS: By optimization of the PAV and VV interval, the LV dP/dt(max) increased from 639 +/- 204 to 789 +/- 223 mmHg/s (+23%; P = 0.0000002). The optimized PAV was 149 +/- 19 ms; the optimized SAV was 100 +/- 20 ms and the corresponding LV dP/dt(max) at this interval was 774 +/- 204 ms (+21%; P = 0.000004). LV dP/dt(max) at optimized SAV - 20 ms and optimized SAV + 20 ms was 747 +/- 213 mmHg/s (P = 0.00004) and 751 +/- 203 mmHg/s (P = 0.0000003), respectively. The mean difference in optimized PAV and optimized SAV was 49 +/- 17 ms, ranging from 20 to 80 ms. CONCLUSIONS: The QRS morphology at optimized PAV can be used as a template to determine the optimal SAV, provided that the patient has normal AV conduction.     

Contribution of Atrioventricular Synchrony to Left Ventricular Systolic Function in a Closed-Chest Canine Model of Complete Heart Block: Implications for Single-Chamber Rate-Variable Cardiac Pacing

This study assessed the impact of atrioventricular (AV) synchrony on characteristics of left ventricular (LV) systolic function during ventricular pacing over a wide heart rate range in a conscious closed-chest canine model of complete AV block. Ten healthy adult dogs underwent thoracotomy during which complete AV block was created by formaldehyde injection, and paired ultrasonic sonomicrometers were positioned on the LV anterior-posterior minor axis. Following recovery from surgery, peak and end-diastolic LV transmural pressure, maximum dP/dt, stroke work, end-diastolic minor axis dimension, and maximum velocity of shortening, were quantitated at heart rates of 80, 100, 120, 140, and 160 beats per minute (bpm) during both ventricular pacing alone and AV sequential pacing with increasing AV intervals (0, 50, 100, 150, 200, 250, and 300 ms). Over the heart rate range tested, parameters of LV systolic function did not differ significantly during ventricular pacing with or without AV synchrony. For example, during ventricular pacing alone maximum LV dP/dt varied from 2110 +/- 70 mmHg/s to 2463 +/- 567 mmHg/s, a range essentially identical to that observed in the presence of AV synchrony. On the other hand, although the impact on LV performance of varying AV interval from 0 to 300 ms was small, differences tended to become more pronounced at higher pacing rates. At 80 bpm, neither stroke work nor maximum LV dP/dt were affected by change in AV interval, while at heart rates greater than or equal to 120 bpm both stroke work and LV dP/dt tended to maximize at AV intervals of 50 and 100 ms and thereafter declined.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increasing left ventricular pacing output decreases interventricular conduction time in patients with biventricular pacing systems

OBJECTIVE: To evaluate the effect of increasing LV pacing output on interventricular timing in patients with biventricular pacing systems. BACKGROUND: Clinical improvement with biventricular pacing is likely related to reduction in ventricular dysynchrony in patients with cardiomyopathy. We hypothesized that increasing left ventricular pacing output would reduce interventricular conduction time and could affect ventricular synchrony. METHODS: Forty-two sequential patients with biventricular pacing systems that permitted independent LV pacing were selected at the time of routine device interrogation. The interval between LV pacing stimulus and onset of the RV electrogram was measured during LV pacing at capture threshold and at maximum pacing output for each patient. RESULTS: The average time from LV pacing stimulus to right ventricular electrogram onset was 142.5 +/- 32.5 ms (range 90-230 ms) at threshold and 132.3 +/- 30.4 ms (range 90-220 ms) at maximum pacing output, with a mean decrease in conduction time of 10.2 +/- 10.9 ms (range 0-45 ms). There was significantly greater interventricular conduction shortening with increased pacing output in patients with ischemic cardiomyopathy compared to others (14.9 +/- 11.9 ms vs 4.0 +/- 4.6 ms; P < 0.01). CONCLUSIONS: Conduction time from LV to RV shortens as LV pacing output is increased. This effect is seen to a greater degree in patients with ischemic cardiomyopathy, possibly related to the presence of myocardial scar near the pacing electrode. Further investigation is needed to assess the clinical outcomes related to this new method for optimizing resynchronization therapy.     

Radial pressure waveform dP/dt max is a poor indicator of left ventricular systolic function

Background The first derivative of left ventricular (LV) pressure over time (dP/dt max) is a marker of LV systolic function that can be assessed during cardiac catheterization and echocardiography. Radial artery dP/dt max has been proposed as a possible marker of LV systolic function and we sought to test this hypothesis. Materials and methods We compared simultaneously recorded radial dP/dt max (by high‐fidelity tonometry) with LV dP/dt max (by high‐fidelity catheter and echocardiography parameters analogous to LV dP/dt max). In study 1, beat‐to‐beat radial dP/dt max and LV dP/dt max were recorded at rest and during supine exercise in 12 males (aged 61 ± 12 years) undergoing cardiac catheterization. In study 2, 2D‐echocardiography and radial dP/dt max were recorded in 54 patients (separate to study 1; 39 men; aged 64 ± 10 years) at baseline and peak dobutamine‐induced stress. Three basal septum measures were taken as being analogous to LV dP/dt max: 1. Peak systolic strain rate; 2. Strain rate (SR‐dP/dt max) during isovolumic contraction (IVCT) and; 3. Tissue velocity during IVCT. Results In study 1 there was a significant difference between resting LV dP/dt max (1461 ± 383 mmHg s⁻¹) and radial dP/dt max (1182 ± 319 mmHg s⁻¹; P < 0·001), and a poor, but statistically significant, correlation between the variables (R² = 0·006; P < 0·05). Similar results were observed during exercise. In study 2 there were weak (R² = −0·12; P = 0·01) to non‐significant associations between radial dP/dt max and all echocardiographic measures analogous to LV dP/dt max at rest or peak stress. Conclusion Radial pressure waveform dP/dt max is not a reliable marker of LV systolic function.     

Stimulation rate and the optimal interventricular interval during cardiac resynchronization therapy in patients with chronic atrial fibrillation

Background: Optimization of cardiac resynchronization therapy (CRT) with respect to the interventricular (V‐V) interval is mainly limited to pacing at a resting heart rate. We studied the effect of higher stimulation rates with univentricular and biventricular (BiV) pacing modes including the effect of the V‐V interval optimization. Methods: In 36 patients with heart failure and chronic atrial fibrillation (AF), the effects of right ventricular (RV), left ventricular (LV), simultaneous BiV, and optimized sequential BiV (BiVopt) pacing were measured. The effect of the pacing mode and the optimal V‐V interval was determined at stimulation rates of 70, 90, and 110 ppm using invasive measurement of the maximum rate of left ventricular pressure rise (LV dP/dt_max). Results: The average LV dP/dt _max for all pacing modalities at stimulation rates of 70, 90, and 110 ppm was 781 ± 176, 833 ± 197, and 884 ± 223 mmHg/s for RV pacing; 893 ± 178, 942 ± 186, and 981 ± 194 mmHg/s for LV pacing; 904 ± 179, 973 ± 187, and 1052 ± 206 mmHg/s for simultaneous BiV pacing; and 941 ± 186, 1010 ± 198, and 1081 ± 206 mmHg/s for BiVopt pacing, respectively. In BiVopt pacing, the corresponding optimal V‐V interval decreased from 34 ± 29, 28 ± 28, and 21 ± 27 ms at stimulation rates of 70, 90, and 110 ppm, respectively . In two individuals, LV dP/dt_max decreased when the pacing rate was increased from 90 to 110 ppm. Conclusion: In patients with AF and heart failure, LV dP/dt_max increases for all pacing modalities at increasing stimulation rates in most, but not all, patients. The rise in LV dP/dt_max with increasing stimulation rates is higher in biventricular (BiV and BiVopt) than in univentricular (LV and RV) pacing. The optimal V‐V interval at sequential biventricular pacing decreases with increasing stimulation rates.     

Systolic and Diastolic Function with Alternate and Combined Site Pacing in the Right Ventricle

We hypothesized that pacing at two ventricular sites simultaneously would activate the myocardium more rapidly and improve ventricular function. We studied the effect of pacing at the right ventricular outflow tract (RYOT) and the RV apex (EVA) on systolic and diastolic function. In 14 patients with a reduced systolic ejection fraction < 40% (mean EF 32%±4%)we measured RV pressures, left ventricular pressures, EF, cardiac output, peak dP/dt, peak negative dP/dt, and the time constant of relaxation, Tau, during intrinsic rhythm, atrial pacing and DVI pacing at the RVA, the RVOT, and both RV sites combined in random order. Repeated measures analysis of variance showed no significant differences in any of these parameters. The highest absolute values of dP/dt were observed during sinus rhythm and the lowest with RVA pacing. This parameter tended to improve progressively with pacing in the RVOT and at both sites. Peak negative dP/dt showed a similar nonsignificant trend. Conclusion: These data suggest that in patients with poor LV function, there may be subtle improvements in diastolic and systolic function with pacing in the RVOT and at combined sites in the RV compared to traditional RVA pacing.     

Prediction of postoperative left ventricular systolic function with Doppler-derived dP/dt in patients with chronic aortic regurgitation.

To evaluate the value of Doppler-derived dP/dt as a predictor of postoperative left ventricular (LV) systolic function in patients with chronic aortic regurgitation, we evaluated 29 patients who underwent aortic valve replacement (n = 17) or valve repair. Doppler-derived dP/dt was determined from the continuous wave Doppler signal of the aortic regurgitation jet preoperatively. Preoperative LV ejection fraction (LVEF) and Doppler-derived dP/dt were 48 +/- 11% and 701 +/- 204 mm Hg/s, respectively. LVEF decreased to 43 +/- 12% at immediate postoperative period and improved to 54 +/- 11% at late postoperative period. In multivariate analysis, only dP/dt was an independent predictor of late postoperative LVEF (r = 0.59, P =.006). A dP/dt 相似文献   

Anodal capture in cardiac resynchronization therapy implications for device programming

INTRODUCTION: Right ventricular (RV) anodal capture (AC) has been reported in cardiac resynchronization therapy (CRT), when left ventricular (LV) pacing uses pseudobipolar (LV tip to RV proximal electrode) configuration. The aim of the study was to analyze the prevalence of AC and its implications for device programming. METHODS AND RESULTS: When AC occurred, the resulting QRS morphology was evaluated with the following pacing modes: (1) LV tip pacing plus RV AC, (2) Biventricular (BiV) pacing (i.e., both LV and RV tip pacing), and (3) BiV pacing plus RV AC. Several interventricular pacing (VV) intervals from 50 ms of LV preactivation to 30 ms of RV preactivation were tested in modes 2 and 3. From 38 consecutive patients, AC was achieved in 14 (in 74% of the pacemakers and in none of the defibrillators). LV tip pacing plus RV AC obtained narrower QRS than BiV pacing at all VV intervals in seven of the patients with AC (50%). When BiV pacing is combined with RV AC, it produced a ventricular depolarization through two wave fronts (one from the LV tip and the second from either the ring or the tip of the RV lead depending on the VV interval programmed). CONCLUSIONS: AC obtained the narrowest QRS of all tested pacing modes in a significant proportion of patients undergoing CRT. Though the stimulus was delivered from three sites (BiV pacing plus RV AC mode), only two wave fronts of ventricular activation were seen by ECG.     

Atrioventricular delay optimization by doppler-derived left ventricular dP/dt improves 6-month outcome of resynchronized patients

BACKGROUND: Atrioventricular (AV) interval optimization, ensuring the best filling and the abolishment of presystolic mitral regurgitation, is crucial for the efficacy of cardiac resynchronization therapy (CRT). The methods proposed to optimize AV delay have many limitations. The maximum left ventricular pressure derivative (LV dP/dt)--an index of cardiac performance--could provide a clue for AV optimization. DP/dt can be calculated by the Doppler curve of mitral regurgitation jet and it is related to micromanometer-derived dP/dt. AIM: The aim of this study was to assess whether optimal AV delay, defined as the highest noninvasive dP/dt, may provide clinical and functional benefits in CRT patients. METHODS: Of 41 consecutive patients, 23 echo Doppler recordings were obtained at AV delays of 60, 80, 100, 120, 140, 160, 180 ms (Group I). Three patients were discarded because of suboptimal Doppler signal. In 15 patients an empiric AV delay of 120 ms was chosen (Group II). Both groups were programmed to atriosynchronous pacing mode and synchronous VV stimulation. RESULTS: In Group I optimal AV delay was 60 ms in one patient, 80 ms in 6, 100 in 6, 120 in 8, 140 in 2. At 6 months follow-up, Group I showed a significantly lower NYHA class (2.1 +/- 0.1 vs 3 +/- 0.2 P < 0.01) and higher LV ejection fraction (LVEF): 32.1 + 1 versus 27.5 +/- 1.6% (P < 0.05) as compared to Group II. CONCLUSIONS: Doppler-derived dP/dt for AV delay optimization determines better functional class and LVEF at 6 months follow-up relative to an empiric AV delay program.     

Right ventricular dP/dt/P(max), not dP/dt(max), noninvasively derived from tricuspid regurgitation velocity is a useful index of right ventricular contractility.

BACKGROUND: Although right ventricular (RV) contractility is important in determining functional capacity, few quantification methods are clinically available. RV dP/dt(max) can be assessed by Doppler echocardiography by using tricuspid regurgitation (TR) but is not routinely used because of its dependency on a Doppler incident angle and preload. Doppler-derived dP/dt/P(max) is relatively insensitive to preload and theoretically independent of the incident angle. We investigated the clinical feasibility of this index as an RV contractility index. METHODS: We computed RV dP/dt(max) and dP/dt/P(max) from the TR-derived RV pressure in 68 patients with dominant RV failure (13 in New York Heart Association [NYHA] class I, 33 in class II, 17 in class III, and 5 in class IV). Peak oxygen consumption (peak VO(2)) was measured in 20 patients during a maximal bicycle ergometer test. RESULTS: dP/dt(max) did not significantly correlate with NYHA class. In contrast, dP/dt/P(max) decreased monotonically with the functional class (r = -0.49, P <.0001), and correlated with peak VO(2) (r = 0.66, P <.002). CONCLUSION: TR-derived dP/dt/P(max), not dP/dt(max), is a clinically useful index of RV contractility, allowing researchers to account for the functional capacity.     

Depression of systolic and diastolic myocardial reserve during atrial pacing tachycardia in patients with dilated cardiomyopathy.

Previous reports have shown that increases in heart rate may result in enhanced left ventricular (LV) systolic and diastolic performance. To assess whether this phenomenon occurs in the presence of depressed LV function, the effects of pacing on LV pressure and volume were compared in seven patients with dilated cardiomyopathy (LV ejection fraction 0.19 +/- 0.11) and six patients with no or minimal coronary artery disease (LV ejection fraction 0.69 +/- 0.11). Patients with normal LV function demonstrated significant increases in LV peak-positive dP/dt, LV end-systolic pressure-volume ratio, LV peak filling rate, and a progressive leftward and downward shift of their pressure-volume diagrams, compatible with increased contractility and distensibility in response to pacing tachycardia. There was no change in LV peak-negative dP/dt or tau. Patients with dilated cardiomyopathy, in contrast, demonstrated no increase in either LV peak-positive dP/dt or the end-systolic pressure-volume ratio, and absence of a progressive leftward shift of their pressure-volume diagrams. Moreover, cardiomyopathy patients demonstrated no increase in LV peak-negative dP/dt or LV peak filling rate and a blunted downward shift of the diastolic limb of their pressure-volume diagrams. Tau, as determined from a derivative method, became abbreviated although never reaching control values. We conclude that patients with dilated cardiomyopathy may demonstrate little or no significant enhancement in systolic and diastolic function during atrial pacing tachycardia, suggesting a depression of both inotropic and lusitropic reserve.     

Morphology of the RV electrogram during LV pacing is related to the hemodynamic effect in cardiac resynchronization therapy

Background: Biventricular (BiV) pacing and left ventricular (LV) pacing both improve LV function in patients with heart failure and LV dyssynchrony. We studied the hemodynamic effect of the atrioventricular (AV) interval and the associated changes in the right ventricular (RV) electrogram (EGM) during LV pacing and compared this with the hemodynamic effect of optimized sequential BiV pacing.
Methods: In 16 patients with New York Heart Association (NYHA) class II to IV, sinus rhythm with normal AV conduction, left bundle branch block (LBBB), QRS > 130 ms, and optimal medical therapy, the changes in RV EGM during LV pacing with varying AV intervals were studied. The hemodynamic effect associated with these changes was evaluated by invasive measurement of LVdP/dt_max and compared with the result of optimized sequential BiV pacing in the same patient.
Results: All patients showed electrocardiographic fusion during LV pacing. The morphology of the RV EGM showed changes in the RV activation that indicated a shift in the extent of fusion from LV pacing. These changes were associated with significant changes in LVdP/dt_max. Baseline LV dP/dt_max was 734 ± 177 mmHg/s, which increased to 927 ± 202 mmHg/s (P<0.0001) with optimized LV pacing and to 920 ± 209 mmHg/s (P<0.0001) with optimized sequential BiV pacing.
Conclusion: The RV EGM is a proper indicator for intrinsic activation over the right bundle during LV pacing and reveals the transition to fusion in the RV EGM that is associated with a decrease in LVdP/dt_max. The hemodynamic effect of optimized LV pacing is equal to optimized sequential BiV pacing.     

Activation sequence modification during cardiac resynchronization by manipulation of left ventricular epicardial pacing stimulus strength

BACKGROUND: Success of cardiac resynchronization therapy (CRT) depends on altering electrical ventricular activation (VA) to achieve mechanical benefit. That increases in stimulus strength (SS) can affect VA has been demonstrated previously in cardiomyopathy patients undergoing ablation. OBJECTIVE: To determine whether increasing SS can alter VA during CRT. METHODS: In 71 patients with CRT devices, left ventricle (LV) pacing was performed at escalating SS. Timing from pacing stimulus to right ventricular (RV) electrogram, ECG morphology, and maximal QRS duration on 12 lead ECG were recorded. RESULTS: Demographics: Baseline QRS duration 153 +/- 25 ms, ischemic cardiomyopathy 48%, ejection fraction 24%+/- 7%. With increased SS, conduction time from LV to right ventricle (RV) decreased from 125 +/- 56 ms to 111 +/- 59 ms (P = 0.006). QRS duration decreased from 212 +/- 46 ms to 194 +/- 42 ms (P = 0.0002). A marked change in QRS morphology occurred in 11/71 patients (15%). The RV ring was the anode in 6, while the RV coil was the anode in 5. Sites with change in QRS morphology showed decrease in conduction time from LV to RV from 110 +/- 60 ms to 64 +/- 68 ms (P = 0.04). Twelve patients (16%) had diaphragmatic stimulation with increased SS. CONCLUSIONS: Increasing LV SS reduces QRS duration and conduction time from LV to RV. Recognition of significant QRS morphology change is likely clinically important during LV threshold programming to avoid unintended VA change.     

Addition of a left ventricular lead to conventional pacing systems in patients with congestive heart failure: feasibility,safety, and early results in 60 consecutive patients

Left bundle branch block worsens congestive heart failure (CHF) in patients with LV dysfunction. Asynchronous LV activation produced by RV apical pacing leads to paradoxical septal motion and inefficient ventricular contraction. Recent studies show improvement in LV function and patient symptoms with biventricular pacing in patients with CHF. The aim of this study was to determine the feasibility, safety, acute efficacy, and early effect on symptoms of the upgrade of a chronically implanted RV pacing system to a biventricular system. Sixty patients with NYHA Class III and IV underwent the upgrade procedure using commercially available leads and adapters. The procedure succeeded in 54 (90%) of 60 patients. Acute LV stimulation thresholds obtained from leads placed along the lateral LV wall via the coronary sinus compare favorably to those reported in current biventricular pacing trials. The complication rate was low (5/60, 8.3%): lead dislodgement (n = 1), pocket hematoma (n = 1), and wound infections (n = 3). During 18 months of follow-up (16.7%) of 60 patients died. Two patients that died failed the initial upgrade attempt. At 3-month follow-up, quality of life scores improved 31 +/- 28 points (n = 29), P < 0.0001). NYHA Class improved from 3.4 +/- 0.5 to 2.4 +/- 0.7 (P = < 0.0001) and ejection fraction increased from 0.23 +/- 0.8 to 0.29 +/- 0.11 (P = 0.0003). Modification of RV pacing to a biventricular system using commercially available leads and adapters can be performed effectively and safely. The early results of this study suggest patients may benefit from this procedure with improved functional status and quality of life.     

Assessment of right ventricular function during exercise with quantitative Doppler tissue imaging in children late after repair of tetralogy of Fallot.

Doppler tissue imaging (DTI) has been developed to assess ventricular wall-motion velocity quantitatively for patients with various types of heart disease. This technique has a possibility of assessing right ventricular (RV) function reserve during exercise. To investigate RV function during exercise using DTI, 21 patients (9.3 +/- 3.3 years) who had undergone operation for tetralogy of Fallot at 1 to 3 years of age and 19 age-matched healthy children were studied. Echocardiography combined with DTI was performed at rest and during supine bicycle submaximal exercise. DTI of tricuspid annulus movement during systole (Sa) was obtained from a 4-chamber view. RV pressure was estimated by maximal tricuspid regurgitation (TR) velocity. The peak value of the first derivation of RV pressure (peak dP/dt) was measured from the continuous wave Doppler-derived TR profile. Adequate spectral Doppler recordings of TR were obtained in all participants. However, 9 healthy children and 2 patients with tetralogy of Fallot were excluded from the study because of an inability to determine the entire spectral TR velocity envelope during exercise. Therefore, data were analyzed in 29 participants. At rest, the mean RV pressure for patients was higher than that in control subjects (27 +/- 4 vs 18 +/- 3 mm Hg, P <.01). The mean Sa and RV peak dP/dt for patients were lower than those in control subjects (6.7 +/- 1.6 vs 8.8 +/- 1.7 cm/s and 464 +/- 77 vs 550 +/- 80 mm Hg/s, P <.01, respectively). Sa and RV peak dP/dt in the two groups increased significantly during exercise. However, the magnitude of increases in Sa and peak dP/dt was significantly less for patients than in control subjects (37 +/- 16 vs 66 +/- 19% and 42 +/- 10 vs 80 +/- 13%, P <.01, respectively). The magnitude of increase in Sa correlated with that in RV peak dP/dt (r = 0.84, P <.01). Results of DTI show high correlation with RV peak dP/dt during exercise. This technique has a potential as a useful indicator of the effect of exercise on RV systolic function. An insufficient increase in Sa suggests impaired response to exercise of RV in patients with tetralogy of Fallot.     

Intracavitary contrast intensity after transpulmonary transmission of a second-generation contrast agent at normal and reduced myocardial contractility.

In this closed-chest preparation in 10 anesthetized pigs, we determined the effects of left ventricular (LV) contractility changes on the echocardiographic contrast intensity variation of a second-generation contrast agent within the LV cavity. The peak positive rate of change in LV pressure (dP/dt(max)), as an index of the isovolumetric phase, was gradually reduced by administration of halothane and propranolol, and the velocity of circumferential fiber shortening (Vcfs) was referenced as an index for the LV ejection phase. Contrast intensity-time curves of the LV cavity were obtained after transpulmonary transmission of the contrast agent. An off-line densitometric method was performed to determine peak maximum and minimum intensities (I(max), I(min)) and their difference (I(amp)). Compared with baseline values, at reductions in dP/dt(max) of 50% and 75%, the contrast intensity parameters I(max), I(min), and I(amp) were decreased by 23% +/- 6% and 44% +/- 5%, 24% +/- 5% and 44% +/- 3%, and 31% +/- 6% and 45% +/- 3%, respectively (P <.05). Significant correlations were observed between I(amp) and dp/dt(max) (r = 0.82, P <.003, n = 30) and their changes (r = 0.59, P <.03, n = 20), but correlations between contrast indexes and Vcfs were only moderate. The sensitivity of I(amp) to indicate changes in dP/dt(max) and Vcfs was 0.95 and 0.83, respectively. The cyclic variation of LV intracavitary contrast intensity reflects the isovolumetric contraction phase better than the ejection phase. The results suggest that measurements of cyclic intensity changes may contribute to the assessment of myocardial contractility changes. Underlying biophysical mechanisms and load dependency of this phenomenon require further investigation.     

Evaluation of cardiac function by tissue Doppler echocardiography: hemodynamic determinants and clinical application

A total of 32 patients without regional wall motion abnormality of the left ventricle underwent sequential tissue Doppler echocardiography and cardiac catheterization. Peak velocities of systolic (Sa), early diastolic (Ea), and late diastolic (Aa) motion of the mitral annulus were measured. Normal references for Sa, Ea and Aa were obtained from 138 volunteers. Indices of left ventricular (LV) systolic and diastolic function were evaluated using high-fidelity LV pressure and volume signals. By multivariate analysis, Sa, Ea and As were significantly and independently related to the maximum of the first derivative of pressure over time (dP/dt(max)), LV relaxation time constant (tau), and LV ejection fraction (EF), respectively. Using the fifth percentiles of the age-stratified normal references as cut-offs, low Sa, low Ea and low Aa identified declined dP/dt(max), prolonged tau and reduced EF, respectively, with good sensitivities and specificities. In conclusion, mitral annulus velocities by tissue Doppler echocardiography can be used to identify patients with declined dP/dt(max), prolonged tau and reduced EF.     

Physiological range of mechanical synchronicity of the human heart: comparison between different echocardiographic assessment modalities

Tissue Doppler was performed to assess physiological ranges of mechanical synchronicity in 47 patients aged 38 to 81 y with normal coronary angiograms, ECG recordings and echocardiographic findings. Maximal time delays between two different left ventricular (LV) walls in long axis time-to-peak tissue displacement (TD_D), respectively in time-to-peak strain (TD_S), time-to-peak strain rate (TD_SR), time-to-peak systolic (TD_VS) and early diastolic (TD_VE) velocities of basal and midwall segments were determined as values corrected for heart rate in a 16-segment LV model and in the right ventricle (RV). Strain (TD_S: LV = 212 +/- 108 ms, RV = 195 +/- 15 ms) and strain rate (TD_SR: LV = 183 +/- 67 ms, RV = 120 +/- 60 ms) showed the highest dyssynchrony values (TD_D: LV = 110 +/- 96 ms, RV = 42 +/- 38 ms; TD_VS: LV = 82 +/- 47 ms, RV = 36 +/- 36 ms; TD_VE: LV = 73 +/- 36 ms, RV = 46 +/- 20 ms) in both ventricles. There was no significant association between a certain LV wall and the occurrence of the earliest, respectively latest peak values of any parameter.     

Alterations in left ventricular diastolic function in conscious dogs with pacing-induced heart failure.

We investigated in conscious dogs (a) the effects of heart failure induced by chronic rapid ventricular pacing on the sequence of development of left ventricular (LV) diastolic versus systolic dysfunction and (b) whether the changes were load dependent or secondary to alterations in structure. LV systolic and diastolic dysfunction were evident within 24 h after initiation of pacing and occurred in parallel over 3 wk. LV systolic function was reduced at 3 wk, i.e., peak LV dP/dt fell by -1,327 +/- 105 mmHg/s and ejection fraction by -22 +/- 2%. LV diastolic dysfunction also progressed over 3 wk of pacing, i.e., tau increased by +14.0 +/- 2.8 ms and the myocardial stiffness constant by +6.5 +/- 1.4, whereas LV chamber stiffness did not change. These alterations were associated with increases in LV end-systolic (+28.6 +/- 5.7 g/cm2) and LV end-diastolic stresses (+40.4 +/- 5.3 g/cm2). When stresses and heart rate were matched at the same levels in the control and failure states, the increases in tau and myocardial stiffness were no longer observed, whereas LV systolic function remained depressed. There were no increases in connective tissue content in heart failure. Thus, pacing-induced heart failure in conscious dogs is characterized by major alterations in diastolic function which are reversible with normalization of increased loading condition.