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.     

Pacemaker optimization in nonresponders to cardiac resynchronization therapy: left ventricular pacing as an available option

Background: Echocardiographic (ECHO)‐guided pacemaker optimization (PMO) in cardiac resynchronization therapy (CRT) nonresponders acutely improves left ventricular (LV) function. However, the chronic results of LV pacing in this group are less understood. Methods: We retrospectively studied 28 CRT nonresponders optimized based on ECHO to LV pacing and compared them to 28 age‐ and gender‐matched patients optimized to biventricular (BiV) pacing. ECHOs with tissue Doppler imaging assessed LV hemodynamics before, immediately after, and 29 ± 16 months after PMO. Also, 56 age‐ and gender‐matched CRT responders were included for comparison of clinical outcomes. Results: PMO resulted in acute improvements in longitudinal LV systolic function and several measures of dyssynchrony, with greater improvements in the LV paced group. Chronic improvements in ejection fraction (EF) (3.2 ± 7.7%), and left ventricle end‐systolic volume (LVESV) (?11 ± 36 mL) and one dyssynchrony measure were seen in the combined group. Chronically, both LV and BiV paced patients improved some measures of systolic function and dyssynchrony although response varied between the groups. Survival at 3.5 years was similar (P = 0.973) between the PMO (58%) and nonoptimized groups (58%) but survival free of cardiovascular hospitalization was significantly (P = 0.037) better in the nonoptimized group. Conclusions : CRT nonresponders undergoing PMO to either LV or BiV pacing have acute improvements in longitudinal systolic function and some measures of dyssynchrony. Some benefits are sustained chronically, with improvements in EF, LVESV, and dyssynchrony. A strategy of ECHO‐guided PMO results in survival for CRT nonresponders similar to that of CRT patients not referred for PMO. (PACE 2012; 35:685–694))     

Video-assisted thoracoscopic implantation of the left ventricular pacing lead for cardiac resynchronization therapy

Background: To study the feasibility and efficacy of video-assisted thoracoscopic (VAT) placement of the left ventricular pacing lead for cardiac resynchronization therapy (CRT) where the conventional transvenous coronary sinus approach has failed.
Methods: Seventeen patients underwent the VAT procedure. Indications for CRT were ischemic cardiomyopathy in six patients and nonischemic cardiomyopathy in 11. The procedure was performed under general anesthesia with single-lung ventilation. Three 2-cm incisions were used on the left chest wall to place the screw-in lead near the obtuse marginal arteries high on the lateral wall of the left ventricle (LV).
Results: The VATS approach was successful in 13/17 (76%) patients. Median procedure time was 75 minutes (range 55–135). A learning curve was observed that appeared to plateau at 75 minutes procedure time after four cases. Median length of hospital stay was 2 days (range 2–8) with one patient requiring intensive care. Satisfactory thresholds and impedances of 2.3 ± 0.9 V/0.5 ms and 560 ohms, respectively, were achieved at mean follow-up of 226 days. All patients reported symptomatic benefit with reduction in New York Heart Association score from III preoperatively to II postoperatively.
Conclusions: VAT placement of the epicardial pacing lead is feasible, safe, and efficacious. It should be considered in cases where the transvenous route has failed or as an alternative in prolonged or hazardous transvenous procedures.     

Transseptal left ventricular endocardial pacing reduces dispersion of ventricular repolarization

Background: Cardiac resynchronization therapy (CRT) may be proarrhythmic in some patients. This may be due to the effect of left ventricular (LV) epicardial pacing on ventricular repolarization. The purpose of this study was to evaluate the effect of endocardial versus epicardial LV biventricular pacing on surface electrocardiogram (ECG) parameters that are known markers of arrhythmogenic repolarization. Methods: ECG markers of repolarization (QT dispersion, QTD; T peak to end, T_peak‐end; T_peak‐end dispersion, T_peak‐endD; QTc) were retrospectively measured before and after CRT in seven patients with transseptal LV endocardial leads (TS group), 28 matched patients with coronary sinus (CS) LV leads (CS group), and eight patients with surgical LV epicardial leads (SUR group). All ECGs were scanned and analyzed using digital callipers. Results: Compared to the CS group, the TS group CRT was associated with a significant postpacing reduction in QTD (?45.2 ± 35.6 vs ?4.3 ± 43.6 ms, P = 0.03) and T_peak‐end (?24.2 ± 22.1 vs 3.4 ± 26.7 ms, P = 0.02). There was a nonsignificant post‐CRT reduction in both T_peak‐endD (?11.3 ± 31.0 vs 2.4 ± 28.9 ms, P = 0.27) and QTc (?50.0 ± 46.4 vs 4.4 ± 70.2 ms, P = 0.06) in the TS versus the CS group. In contrast, there were no differences between the SUR and CS groups in terms of the effect of CRT on these repolarization parameters. Conclusions: CRT with (atrial transseptal) endocardial LV lead placement is associated with repolarization characteristics that are considered to be less arrhythmogenic than those generated by CS (epicardial) LV lead placement. Further work is needed to determine whether these changes translate to a reduction in proarrhythmia. (PACE 2011; 34:1258–1266)     

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.     

Use of a retained guidewire to improve the left ventricular pacing threshold

Although transvenous access to the coronary veins has considerably simplified left ventricular (LV) pacing, it can remain a time consuming and arduous task achieving satisfactory pacing positions for the LV electrode. Common problems include negotiating small veins with adequate guide catheter stability, pacing electrode stability once positioned, and phrenic nerve stimulation. We report a case where use of the pacing lead guidewire resulted in a dramatic reduction in the pacing threshold of the LV lead, and saved the patient the need to undergo thoracotomy placement.     

Invasive optimization of cardiac resynchronization therapy: role of sequential biventricular and left ventricular pacing

BACKGROUND: Aim of this invasive study was to characterize and quantify changes in left ventricular (LV) systolic function due to sequential biventricular pacing (BV) as compared to right atrial triggered simultaneous BV (BV(0)), LV, and right ventricular (RV) pacing in patients with congestive heart failure (CHF). METHODS: In 22 CHF patients, all in sinus rhythm, temporary multisite pacing was performed prior to implantation of a permanent system. LV systolic function was evaluated invasively by the maximum rate of LV pressure increase (dP/dt(max)). Sequential BV pacing was performed with preactivation of either ventricle at 20-80 ms. RESULTS: In comparison to RV pacing, LV and BV(0) pacing increased dP/dt(max) by 33.9 +/- 19.3% and 34.0 +/- 22.6%, respectively (P < 0.001). In 9 patients, optimized sequential BV pacing further improved dP/dt(max) by 8.5 +/- 4.8% compared to BV(0) (range 3.3-17.1, P < 0.05). In 10 patients exhibiting a PR interval < or =200 ms, LV pacing was either superior (n = 6) or equal to BV(0) pacing (n = 4). In these 10 patients, LV pacing yielded a 7.4 +/- 8.0% higher dP/dt(max) than BV(0) pacing (P < 0.05). CONCLUSIONS: Using sequential BV pacing, generally with LV preactivation, moderate improvements in LV systolic function can be achieved in selected patients. Baseline PR interval may aid in the selection of the optimum cardiac resynchronization therapy (CRT) mode, favoring LV pacing in patients with a PR interval < or =200 ms.     

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.     

Anodal right ventricular capture during left ventricular stimulation in CRT-implantable cardioverter defibrillators

BACKGROUND: Cardiac resynchronization therapy (CRT) has been shown to improve symptoms of patients with moderate to severe heart failure. Optimal CRT involves biventricular or left ventricular (LV) stimulation alone, atrio-ventricular (AV) delay optimization, and possibly interventricular timing adjustment. Recently, anodal capture of the right ventricle (RV) has been described for patients with CRT-pacemakers. It is unknown whether the same phenomenon exists in CRT systems associated with defibrillators (CRT-ICD). The RV leads used in these systems are different from pacemaker leads: they have a larger diameter and shocking coils, which may affect the occurrence of anodal capture. METHODS: We looked for anodal RV capture during LV stimulation in 11 consecutive patients who received a CRT-ICD system with RV leads with a true bipolar design. Fifteen patients who had RV leads with an integrated design were used as controls. Anodal RV and LV thresholds were determined at pulse width (pw) durations of 0.2, 0.5, and 1.0 ms. RESULTS: RV anodal capture during LV pacing was found in 11/11 patients at some output with true bipolar RV leads versus 0/15 patients with RV leads with an integrated bipolar design. Anodal RV capture threshold was more affected by changes in pw duration than LV capture threshold. In CRT-ICD systems, RV leads with a true bipolar design with the proximal ring also used as the anode for LV pacing are associated with a high incidence of anodal RV capture during LV pacing. This may affect the clinical response to alternative resynchronization methods using single LV stimulation or interventricular delay programming.     

Atrial transseptal left ventricular lead implantation for cardiac resynchronization therapy using arteriovenous loop technique

To date, several techniques for transseptal left ventricular (LV) endocardial pacing for cardiac resynchronization therapy (CRT) have been proposed in patients for whom routine transvenous LV pacing is infeasible. These techniques are of varying difficulty and complexity, and some requires devices not easily accessible. We herein report a simple, safe and effective approach of atrial transseptal LV lead implantation using arteriovenous loop technique in a patient for whom transvenous LV implantation lead had failed.     

The deleterious consequences of right ventricular apical pacing: time to seek alternate site pacing

BACKGROUND: The purpose of this article is to critically review the data accumulated to date from studies evaluating the hemodynamic and clinical effects of right ventricular apical pacing during conventional permanent cardiac pacing. The data from studies comparing the effects of right ventricular apical pacing and alternate site ventricular pacing are also reviewed. METHODS: We conducted a MEDLINE and journal search of English-language reports published in the last decade and searched relevant papers. RESULTS: Although intraventricular conduction delay in the form of left bundle branch block (LBBB) has traditionally been viewed as an electrophysiologic abnormality, it has now become abundantly clear that it has profound hemodynamic effects due to ventricular dyssynchrony, especially in patients with heart failure. These deleterious effects can be significantly ameliorated by cardiac resynchronization therapy effected by biventricular or left ventricular pacing. However, not only is spontaneous LBBB harmful, but the iatrogenic variety produced by right ventricular apical pacing in patients with permanent pacemakers may be equally deleterious. In this review new evidence from recent studies is presented, which strongly suggests a harmful effect of our long-standing practice of producing an iatrogenic LBBB by conventional right ventricular apical pacing in patients receiving permanent pacemakers. This emerging strong new evidence about the adverse hemodynamic and clinical effects of right ventricular apical pacing would dictate a reassessment of our traditional approach to permanent cardiac pacing and direct our attention to alternate sites of pacing, such as the left ventricle and/or the right ventricular outflow tract or septum, if not for all patients, at least for those with left ventricular dysfunction. Indeed, current convincing data on alternate site ventricular pacing are encouraging and this approach should be actively pursued and further investigated in future studies. CONCLUSIONS: Not only is spontaneous permanent LBBB harmful to our patients, but the iatrogenic variety produced by right ventricular apical pacing during conventional permanent pacing may also be deleterious to some patients. The compelling evidence presented herein cannot be ignored; it may dictate a change of attitude toward right ventricular apical pacing directing our attention to alternate sites of ventricular pacing and avoidance of the right ventricular apex.     

Predictors of a positive response to biventricular pacing in patients with severe heart failure and ventricular conduction delay

BACKGROUND: Cardiac resynchronization therapy (CRT) is recommended in patients with ejection fraction <35%, QRS width> 120 ms, and New York Heart Association (NYHA) functional class III or IV despite optimal medical therapy. We aimed to define demographic, clinical, and electrocardiographic predictors of positive clinical response to CRT. METHODS AND RESULTS: Hundred consecutive patients fulfilling the recommended criteria were implanted with a CRT device. Demographic, clinical, two-dimensional echocardiographic and electrographic parameters were measured at baseline and after 6 months of simultaneous biventricular pacing. A positive response to CRT included an improvement of at least one NYHA functional class associated with an absence of hospitalization for worsening heart failure. At the end of follow-up, 12 patients were dead and 71% of the patients were classified as responders. After 6 months of CRT, the ejection fraction was significantly higher (P = 0.035) in responders versus nonresponders. Multivariate analysis identified three independent predictors of positive response to CRT: an idiopathic origin of the cardiomyopathy (P = 0.043), a wider QRS before implantation (P = 0.017), and a narrowing of the QRS after implantation (P = 0.037). CONCLUSION: An idiopathic origin of the cardiomyopathy, a wider QRS before implantation, and a narrowing of the QRS width after implantation were identified as independent predictors of clinical positive response to CRT.     

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.     

Resynchronization therapy after congenital heart surgery to improve left ventricular function

This report describes the mid-term beneficial hemodynamic effect of biventricular pacing in an infant with congestive heart failure after congenital heart surgery, due to resynchronization of the left and right ventricle, optimization of the AV delay, and (partial) correction of the LV dyssynchrony.     

Simple access to the coronary venous system for left ventricular pacing

Implantation of the LV lead for biventricular pacing can be challenging, time consuming, and often requires extensive fluoroscopy time. A conventional diagnostic 5 Fr left Amplatz catheter was used to cannulate the coronary sinus in 15 consecutive patients undergoing implantation of a biventricular pacemaker. When the coronary sinus was cannulated, the proximal end of the Amplatz catheter was cut and the coronary sinus sheath was passed over the Amplatz catheter that was then removed. Coronary sinus cannulation was achieved in all 15 patients with a mean fluoroscopy time of 3.34 +/- 1.9 minutes. Subsequent implantation of a biventricular pacemaker was successful and free of complications in all the 15 patients.     

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.