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.     

Perioperative biventricular pacing leads to improvement of hemodynamics in patients with reduced left-ventricular function--interim results

BACKGROUND: Cardiac resynchronization therapy (CRT) has been introduced as a new therapeutic modality in patients with chronic heart failure. However, most studies have investigated the hemodynamic effects in congestive, but not postoperative heart failure. OBJECTIVE: The following study investigates hemodynamic effects of perioperative temporary biventricular pacing in patients undergoing open heart surgery.In 54 patients one left and one right ventricular epicardial wire was placed during open heart operations. Hemodynamic parameters were measured immediately after the operation and 6 as well as 24 hours postoperatively. Transesophageal echocardiography was performed 1 hour postoperatively. RESULTS: Of the 54 patients (59.2%), 32 responded to biventricular pacing with an increase in cardiac output; in these patients synchronized ventricular contraction could be verified echocardiographically. This hemodynamic benefit persisted 6 hours and 24 hours postoperatively. The remaining 22 patients did not show any hemodynamic improvement from biventricular stimulation. CONCLUSION: Biventricular pacing leads to significant rise in cardiac output in approximately 59% of patients with severely reduced left ventricular function and widened QRS complexes. Further studies are necessary to define clearly the clinical characteristics of patients who show remodeling by CRT.     

Latency during left ventricular pacing from the lateral cardiac veins: a cause of ineffectual biventricular pacing

We report three patients with cardiomyopathy and pronounced stimulus to QRS latency during left ventricular (LV) pacing from an epicardial cardiac vein. Delayed LV activation during simultaneous biventricular pacing produced an electrocardiographic pattern dominated by right ventricular stimulation. Hemodynamic parameters improved immediately after advancing LV stimulation (in one patient) or pacing the LV only (in two patients) coupled with dramatic improvement of heart failure symptoms.     

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.     

Right heart failure due to loss of right ventricular capture in a patient with atrioventricular junction ablation and biventricular pacing

We describe the case of a patient with atrioventricular (AV) junction ablation and chronic biventricular pacing in which intermittent dysfunction of the right ventricular (RV) lead resulted in left ventricular (LV) stimulation alone and onset of severe right heart failure. Restoration of biventricular pacing by increasing device output and then performing lead revision resolved the issue. This case provides evidence that LV pacing alone in patients with AV junction ablation may lead to severe right heart failure, most likely as a result of iatrogenic mechanical dyssynchrony within the RV. Thus, probably this pacing mode should be avoided in pacemaker-dependent patients with heart failure.     

Upgrade of a chronic unipolar pacemaker to a biventricular pacemaker system

With the development of cardiac resynchronization for patients with symptomatic heart failure and electrical dyssynchrony, there are patients with chronic pacemakers that meet the indications for biventricular pacing. Typically, this involves placement of the left ventricular lead with generator change to a dual chamber biventricular pacemaker, maintaining use of the right-sided leads. There are patients with older pacemaker systems that have unipolar leads with 5/6-mm pin connectors. These patients present challenges to upgrade that are separate from typical IS-1 system upgrades. Currently there are no pacemakers manufactured that accept the chronic 5/6-mm unipolar leads directly with the additional IS-1 left heart lead. This report presents one such case in which a combination of adaptor and lead replacement resulted in upgrade to a biventricular system.     

Assessment of regional wall motion by strain Doppler during biventricular pacing in patients with conventional indications for a pacemaker

Biventricular pacing therapy is effective in patients with severe congestive heart failure. Strain Doppler imaging (SDI) is a new tool for measuring regional myocardial deformation. We evaluated regional wall motion by strain Doppler imaging in 13 patients who had conventional indications for a pacemaker (74 +/- 6 years old) and in six with NYHA Class III or IV heart failure with a biventricular pacemaker (HF-RV: during right ventricular pacing, HF-BV: during biventricular pacing). The other seven patients had normal LV function (N-RV). Wall motion was assessed by strain of the myocardium, and the interval between the Q wave of the surface ECG and the peak strain (QPSI) was measured in three septal and three lateral segments. Interventricular contraction delay was determined as the interval between the onset of the left and right ventricular outflow waves. Intraventricular contraction delay was determined as the time difference between minimum and maximum QPSI. Strain of HF-RV was significantly greater than that of N-RV (-9.6%+/- 2.5% vs -14.4%+/- 2.3%, P < 0.0001). Intraventricular contraction delay of HF-RV was significantly greater than that of N-RV (273 +/- 12 vs 151 +/- 69 ms, P = 0.0004). Strain of HF-RV was not significantly greater than that of HF-BV (-9.6% +/- 2.5% vs -10.6% +/- 2.9%). Interventricular contraction delay of HF-RV was greater than that of HF-BV (37.2 +/- 44.7 vs 16.2 +/- 47.4 ms, P < 0.0001). Intraventricular contraction delay of HF-RV was significantly greater than that of HF-BV (322 +/- 101 vs 209 +/- 88 ms, P = 0.0006). In conclusion, biventricular pacing improves both interventricular contraction delay and intraventricular contraction delay in patients with conventional indications for a pacemaker with severe congestive heart failure, and SDI is useful to predict the efficacy of biventricular pacing.     

Transmyocardial voyage of a temporary epicardial lead: an unusual long-term complication

Although the majority of temporary epicardial leads used during cardiac surgery are removed in the perioperative period, occasionally, the wires are cut and allowed to retract into the subcutaneous tissue. Complications arising from such retained epicardial wires are rare. We present a case of transmyocardial migration of a retained epicardial wire through the right ventricular myocardium into the pulmonary artery in a patient who had undergone coronary artery bypass graft surgery 13 years ago. We describe the presentation and successful management of this case.     

Economic analysis of a randomized trial of biventricular pacing in Canada

BACKGROUND: Congestive heart failure (CHF) has been shown to affect 5% of the Canadian adult population, and leads to 9.5 deaths per 100 cardiac-related hospitalizations in Canada. The economic outcomes from biventricular pacing for heart failure are not well understood. This study analyzes resource utilization and related costs associated with CHF for patients who receive standard implantable cardiac defibrillators (ICDs) versus those who receive ICD plus biventricular pacing or cardiac resynchronization therapy (CRT). METHODS: The Canadian analysis of resynchronization therapy in heart failure (CART-HF) study included 72 patients with New York Heart Association class II-IV CHF requiring an ICD. Patients were randomized to receive either ICD + CRT treatment or ICD treatment alone. Medical resource utilization data were collected for 6 months following treatment and were applied to representative costs for the provinces of Quebec and Ontario. Resource utilization was subcategorized into pharmacological therapy, physician visits, hospitalizations, adverse events, and productivity losses. RESULTS: Post-treatment, per patient costs for the CRT + ICD treatment group were less than the follow-up costs for patients receiving ICD treatment only in each province. Mean savings for patients receiving biventricular therapy were CAD 2,420 dollars in Quebec and CAD 2,085 dollars in Ontario during the 6-month follow-up. CONCLUSIONS: These analyses indicate that savings in post-implant health-care utilization (hospitalizations and pharmacological therapy) can offset some of the device and procedural costs associated with CRT devices.     

Sequential biventricular pacing: evaluation of safety and efficacy

The study evaluated the clinical safety, performance, and efficacy of sequential biventricular pacing in the InSync III (Model 8042) biventricular stimulator in a multicenter, prospective 3-month study and assessed the proper functioning of features aiming at improving biventricular AV therapy delivery. The system was successfully implanted in 189 (95.9%) of 198 patients with symptomatic systolic heart failure and a prolonged QRS complex duration. Patients significantly improved their 6-minute hall walk distance (baseline 339 +/- 92 vs 3-month 422 +/- 127 meter, P < 0.001) and NYHA class (baseline 3.1 +/- 0.5 vs 3-month 1.9 +/- 0.7, P < 0.001). Echocardiographic optimization of sequential biventricular pacing showed an improvement in stroke volume compared to simultaneous stimulation (sequential 68 +/- 24 mL vs simultaneous 56 +/- 23 mL, P < 0.001) at baseline and at 3 months. In 88% (30/34) of the patients these improvements were seen within a small range of V-V delays of +/-20 ms and in 94% (32/34) within V-V delays of +/-40 ms. In contrast, programming beyond this range reduced stroke volume below that during simultaneous biventricular pacing. The device functioned as expected. LV lead dislodgement was observed in 12 patients and phrenic nerve stimulation required lead repositioning in 2 patients. Eight patients died during the study. Patient survival at 3 and 6 months was 97 +/- 2% and 94 +/- 2%, respectively. Cause of death was cardiac (n = 7), heart failure related (n = 3), arrhythmia related (n = 2), and unknown (n = 2). In conclusion, this sequential biventricular pacemaker was safe and efficacious.     

Magnetic resonance imaging-based biventricular pacemaker upgrade

This report describes a patient with drug refractory severe chronic ischemic heart failure, atrial fibrillation with bradycardia, and left bundle branch block who had a failed implantation of a biventricular pacemaker because of a high left ventricular pacing threshold. VVI pacemaker implantation had not improved the patient's condition. MRI-guided biventricular pacemaker upgrade had been performed with a left ventricular epicardial lead at the lateral region where a 4-mm thickening during systole had been proven. After 6 months of effective resynchronization, the patient's functional class improved to NYHA II without further need of hospitalization.     

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.     

Performance of left ventricular versus biventricular pacing in chronic heart failure assessed by stress echocardiography

Acute hemodynamic studies suggest that resynchronization therapy using single-site left ventricular pacing (LVP) is equivalent to biventricular pacing (BIVP). The aim of this study was to assess the performance of LVP versus BIVP during exercise by means of stress echocardiography. A total of 28 patients (25 men and 3 women, mean age 60.9 +/- 8 years) with advanced chronic heart failure and impaired ventricular conduction (QRS > 150 ms) were studied. Patients were randomly allocated to either BIVP or LVP mode with a crossover on the next day and cardiac output was estimated at rest and during each stage of bicycle ergometry in supine position by means of velocity time integral formula. Maximum exercise level was comparable for both pacing modes (up to 100 W) and no significant differences were revealed either in heart rate or in blood pressure at rest and during any step of exercise. LVP was associated with significantly higher cardiac output at rest (3.2 +/- 0.5 vs 2.8 +/- 0.6 l/min, P < 0.01) and during low level exercise (4.4 +/- 0.8 vs 3.9 +/- 0.8 l/min at 25 W, P < 0.05) as compared with BIVP. There was a trend towards higher cardiac output for LVP even at higher levels of exercise. These effects were predominantly confined to patients with idiopathic dilated cardiomyopathy. It is concluded that cardiac resynchronization therapy using single-site LVP results in better hemodynamic response as compared with BIVP, both at rest and during physical exercise.     

Prolonged paced QRS duration as a predictor for congestive heart failure in patients with right ventricular apical pacing

BACKGROUND: The recent studies showed that right ventricular (RV) pacing was associated with worsening of heart failure. The aim of this study is to clarify the clinical significance of paced QRS duration during RV pacing to predict congestive heart failure (CHF) patients. METHODS AND RESULTS: This study enrolled in 92 patients with atrioventricular block who underwent initial pacemaker implantation. The paced QRS duration was automatically obtained by electrocardiography immediately after pacemaker implantation and then by routine attendance at a pacemaker clinic every 3 months. The paced QRS duration was positively correlated with left ventricular end-diastolic dimension (P < 0.05) and left ventricular end-systolic dimension (P < 0.05), and tended to negatively correlate with left ventricular ejection fraction (P = 0.0507). The paced QRS duration immediately after pacemaker implantation was 170.4 +/- 18.9 ms. During a mean follow-up period of 53 +/- 16 months, 16 patients developed CHF. We selected as a cut-off value the nearest whole number (190 ms) that was one standard deviation greater than the mean, and divided into two groups according to baseline paced QRS duration. Patients with a paced QRS duration of <190 ms comprised group A (n = 77, nine of which developed CHF) and the remainder comprised group B (n = 15, seven of which developed CHF). Prolonged paced QRS duration (> or =190 ms) was associated with a significant increase in the overall morbidity of CHF (P < 0.05). Additionally, paced QRS duration significantly prolonged during the follow-up period among group A patients with CHF (P < 0.05), but did not change among patients without CHF. CONCLUSION: We concluded that paced QRS duration can be a useful indicator of impaired left ventricular function in patients with RV pacing. Even in patients whose paced QRS duration is relatively shorter, progressive prolongation of paced QRS duration can predict the development of CHF.     

The benefits of biventricular pacing in heart failure patients with narrow QRS, NYHA class II and right ventricular pacing

OBJECTIVE: To identify subgroups of heart failure patients who might benefit from biventricular pacing. BACKGROUND: Cardiac resynchronization therapy (CRT) improves the quality of life, New York Heart Association (NYHA) functional class, and exercise capacity and decreases hospitalizations for heart failure for patients who have severe heart failure and a wide QRS. It is unclear if other populations of heart failure patients would benefit from CRT. METHODS: One hundred forty-four consecutive heart failure patients who underwent CRT and completed 3 months of follow-up were reviewed. Demographic, echocardiographic, electrocardiographic, and clinical outcome data were analyzed to assess the relationship of functional class and QRS duration before device implantation to postimplant outcomes. RESULTS: There were 20, 88, and 36 patients in NYHA functional class II, III, and IV, respectively. Thirty-four patients had right ventricular pacing and another 29 patients had a QRS duration < or = 150 ms. Patients who were in NYHA functional class II at baseline had significant improvement in left ventricular ejection fraction and indices of left ventricular remodeling after CRT. Similar significant findings were seen in the subgroup with right ventricular pacing at baseline after CRT. However, in the subgroup with a narrow QRS duration, there were no significant changes in the indices of left ventricular remodeling or in the NYHA functional class and there was a significant increase in the QRS duration. For the study cohort as a whole, an improvement in NYHA functional class after CRT correlated with a significant decrease in adverse clinical outcomes. CONCLUSIONS: Heart failure patients who were in NYHA functional class II and those with right ventricular pacing appeared to benefit from CRT.     

Basal asynchrony and resynchronization with biventricular pacing predict long-term improvement of LV function in heart failure patients

Biventricular pacing (BiV) is emerging for patients with dilated cardiomyopathy (DCM) and asynchrony. We measured basal asynchrony and early resynchronization by radionuclide angioscintigraphy (RNA) in order to predict long-term evolution of ventricular function after BiV. Thirty-four patients (NYHA Class III-IV,65.4 +/- 11 years) with large QRS(179 +/- 18 ms)were implanted with BiV and studied by RNA before (D0), at day 8 (D8), and during follow-up(20 +/- 7 months). We calculated left and right ejection fractions, the interventricular dyssynchrony (TRVLV), and the apicobasal dyssynchrony (Tab). LVEF improved from 20.2 +/- 8.1%(D0) to27.1%+/- 12.6%(follow-up,P < 0.003 vs D0) and RVEF from 28.6%+/- 13%(D0) to 34.3 +/- 11.5%(follow-up,P < 0.03 vs D0). Inter- (DeltaTRVLV) and intraventricular resynchronization was immediate and remained stable: TRVLV decreased from 68.3 +/- 38 ms(D0) to 13.4 +/- 48.5 ms(D8) and1.8 +/- 39.2 ms(follow-up,P < 0.0001 vs D0); and Tab from 45.8 +/- 64.1 msto-18 +/- 68(D8) and-28.3 +/- 53.6 ms(follow-up,P < 0.0001 vs D0). Early inter- and intraventricular resynchronization (DeltaTab) at D8 were related to late LVEF and RVEF improvement. Together, an LVEF > 15% and a significant interventricular dyssynchrony (TRVLV > 60 ms) at D0 have a sensitivity of 79% and a positive predictive value of 83% to predict an improvement of LVEF superior to 5% at follow-up. In DCM patients, BiV resynchronizes ventricles early and in the long-term, while RVEF and LVEF improve progressively. Patients with large electromechanical dyssynchrony benefit most from BiV.     

Extraction of looped transvenous pacing leads to reduce tricuspid regurgitation

Transvenous leads are a known source of iatrogenic tricuspid regurgitation. It is commonly held that extraction of chronic pacing and defibrillator leads will not reduce this, due to the inevitable trauma to the valve associated with the procedure. We demonstrate three cases of clinically significant reductions in tricuspid regurgitation after extraction of leads that were looped across the tricuspid valve.     

Optimal location for temporary epicardial pacing leads following open heart surgery

Temporary epicardial pacing wires are routinely placed in patients undergoing cardiac surgery. Eighteen suitable patients undergoing elective surgery were prospectively studied. Their sensing and stimulating characteristics were studied at various locations. Subepicardial pacing leads were applied to the lateral wall of the LV, apex of the LV, anterior wall of the RV, diaphragmatic wall of the RV, and diaphragmatic wall of the LV. Impedance, R wave amplitude, slew rate, and stimulation thresholds were measured on postoperative days 1 and 5. Impedance remained unchanged in time with no significant differences between locations. R waves and slew rates were significantly lower in the anterior RV wall. Stimulation thresholds displayed no differences on day 1, but they increased significantly in all locations on day 5. These thresholds were significantly lower in the lateral and diaphragmatic LV walls on day 5, and the rate of voltage increase was also lower in these two locations. Five patients presented phrenic nerve stimulation when stimulating the lateral LV wall. The authors advocate the diaphragmatic wall of the LV as the best location for placing temporary leads. The anterior wall of the RV is not recommended for pacing purposes.