Close Proximity of Left Anterior Descending Artery to the Right Ventricular Lead Apparently Implanted into the Mid-septum

Right ventricular (RV) mid-septal pacing should have fewer negative effects on left ventricular function compared to apical pacing. However, targeting the mid-septum may be technically challenging since it is usually done with two-dimensional fluoroscopy. The rotation of the heart and various shapes of the RV make it difficult to assess, whether the lead is really anchored in the septum. Many leads, apparently anchored in the septum, are in fact anchored in the anterior wall or anteroseptal groove, and some can get anchored in close proximity to the left anterior descending artery (LAD). We report three cases from our series of 51 patients, in whom the RV lead thought to be implanted in the mid-septum was in fact anchored in close proximity of LAD when assessed using computed tomography.     

Permanent direct His bundle pacing: initial report showing technical feasibility of an alternative pacing therapy

To prevent deterioration of left ventricular function during right ventricular apical pacing, permanent direct His bundle stimulation can be considered in selected patients with low left ventricular ejection fraction and a normal His-ventricle conduction time. We describe our first short-term experiences with permanent direct His bundle pacing in three patients. In two patients His bundle stimulation was still effective at six weeks'' follow-up. In one patient loss of capture was registered, after which conventional RV apical pacing was performed.     

Adverse effects of atrioventricular synchronous right ventricular pacing on left ventricular sympathetic activity, efficiency, and hemodynamic status

Right ventricular (RV) pacing is now recognized to play a role in the development of heart failure in patients with and without underlying left ventricular (LV) dysfunction. We used the cardiac norepinephrine spillover method to test the hypothesis that RV pacing is associated with cardiac sympathetic activation. We studied 8 patients with normal LV function using temporary right atrial and ventricular pacing wires. All measurements were carried out during a fixed atrial pacing rate. The radiotracer norepinephrine spillover technique was employed to measure total body and cardiac sympathetic activity while changes in LV performance were evaluated with a high-fidelity manometer catheter. Atrioventricular synchronous RV pacing, compared with atrial pacing alone, was associated with a 65% increase in cardiac norepinephrine spillover, an increase in LV end-diastolic pressure, and a reduction in myocardial efficiency. These responses may play a role in the development of heart failure and poor outcomes that are associated with chronic RV pacing.     

An Approach to the Stepwise Management of Severe Mitral Regurgitation with Optimal Cardiac Pacemaker Function

Right ventricular apical pacing may cause or worsen mitral regurgitation (MR). Potential mechanisms for this adverse sequelae include intraventricular dyssynchrony, altered papillary muscle function, pacing-induced cardiomyopathy with left ventricular dilation, and annular dilation. In contrast, biventricular (BiV) pacing may improve MR presumably by opposing the negative effects. Whether or not left ventricular lead location is important in treating mitral regurgitation in patients with pacemakers is unknown.We report a case of severe MR and left ventricular (LV) systolic failure in a patient with right ventricular pacing. Multiple potential etiologies for the worsening valve function were noted, and a stepwise iterative optimizing scheme that included basal lateral LV pacing improved mitral valve function and ameliorated heart failure symptoms.     

Acute Impact of Pacing at Different Cardiac Sites on Left Ventricular Rotation and Twist in Dogs

Objectives

We evaluated the acute impact of different cardiac pacing sites on two-dimensional speckle-tracking echocardiography (STE) derived left ventricular (LV) rotation and twist in healthy dogs.

Methods

Twelve dogs were used in this study. The steerable pacing electrodes were positioned into right heart through the superior or inferior vena cava, into LV through aorta across the aortic valve. The steerable pacing electrodes were positioned individually in the right atrium (RA), right ventricular apex (RVA), RV outflow tract (RVOT), His bundle (HB), LV apex (LVA) and LV high septum (LVS), individual pacing mode was applied at 10 minutes interval for at least 5 minutes from each position under fluoroscopy and ultrasound guidance and at stabilized hemodynamic conditions. LV short-axis images at the apical and basal levels were obtained during sinus rhythm and pacing. Offline STE analysis was performed. Rotation, twist, time to peak rotation (TPR), time to peak twist (TPT), and apical-basal rotation delay (rotational synchronization index, RSI) values were compared at various conditions. LV pressure was monitored simultaneously.

Results

Anesthetic death occurred in 1 dog, and another dog was excluded because of bad imaging quality. Data from 10 dogs were analyzed. RVA, RVOT, HB, LVA, LVS, RARV (RA+RVA) pacing resulted in significantly reduced apical and basal rotation and twist, significantly prolonged apical TPR, TPT and RSI compared to pre-pacing and RA pacing (all P<0.05). The apical and basal rotation and twist values were significantly higher during HB pacing than during pacing at ventricular sites (all P<0.05, except basal rotation at RVA pacing). The apical TPR during HB pacing was significantly shorter than during RVOT and RVA pacing (both P<0.05). The LV end systolic pressure (LVESP) was significantly lower during ventricular pacing than during pre-pacing and RA pacing.

Conclusions

Our results show that RA and HB pacing results in less acute reduction on LV twist, rotation and LVESP compared to ventricular pacing.     

Biventricular pacing in the early postoperative period after cardiac surgery

Cardiac resynchronization therapy is not commonly used in the early postoperative period in patients undergoing cardiac surgery who have left ventricular (LV) dysfunction and a history of heart failure. We performed a prospective randomized clinical trial to compare atrial synchronous right ventricular (DDD RV) and biventricular (DDD BIV) pacing within 72 hours after cardiac surgery in patients with an EF ≤35 %, a QRS interval longer than 120 msec and who had LV dyssynchrony detected by real-time three-dimensional echocardiography (RT3DE). Epicardial pacing was provided by a modified Medtronic INSYNC III pacemaker. An LV epicardial pacing lead was implanted on the latest activated segment of the LV based on RT3DE. The study included 18 patients with ischemic heart disease, with or without valvular heart disease (14 men, 4 women, average age 71 years). Patients undergoing DDD BIV pacing had a statistically significant greater CO and CI (CO 6.7±1.8 l/min, CI 3.4±0.7 l/min/m(2)) than patients undergoing DDD RV pacing (CO 5.5±1.4 l/min, CI 2.8±0.7 l/min/m(2)), p<0.001. DDD BIV pacing in the early postoperative period after cardiac surgery corrects LV dyssynchrony and has better hemodynamic results than DDD RV pacing.     

Differential effects of left ventricular pacing sites in an acute canine model of contraction dyssynchrony

The goal of the present study was to assess the effects of left ventricular (LV) pacing sites (apex vs. free wall) on radial synchrony and global LV performance in a canine model of contraction dyssynchrony. Ultrasound tissue Doppler imaging and hemodynamic (LV pressure-volume) data were collected in seven anesthetized, opened-chest dogs. Right atrial (RA) pacing served as the control, and contraction dyssynchrony was created by simultaneous RA and right ventricular (RV) pacing to induce a left bundle-branch block-like contraction pattern. Cardiac resynchronization therapy (CRT) was implemented by adding simultaneous LV pacing to the RV pacing mode at either the LV apex (CRTa) or free wall (CRTf). A new index of synchrony was developed via pair-wise cross-correlation analysis of tissue Doppler radial strain from six midmyocardial cross-sectional regions, with a value of 15 indicating perfect synchrony. Compared with RA pacing, RV pacing significantly decreased radial synchrony (11.1 +/- 0.8 vs. 4.8 +/- 1.2, P < 0.01) and global LV performance (cardiac output: 2.0 +/- 0.3 vs. 1.4 +/- 0.1 l/min and stroke work: 137 +/- 22 vs. 60 +/- 14 mJ, P < 0.05). Although both CRTa and CRTf significantly improved radial synchrony, only CRTa markedly improved global function (cardiac output: 2.1 +/- 0.2 l/min and stroke work: 113 +/- 13 mJ, P < 0.01 vs. RV pacing). Furthermore, CRTa decreased LV end-systolic volume compared with RV pacing without any change in LV end-systolic pressure, indicating an augmented global LV contractile state. Thus, LV apical pacing appears to be a superior pacing site in the context of CRT. The dissociation between changes in synchrony and global LV performance with CRTf suggests that regional analysis from a single plane may not be sufficient to adequately characterize contraction synchrony.     

The effects of right ventricular apical pacing on left ventricular function. Stimulation of the right ventricular apex: should it still be the gold standard?

Current pacing practice is undergoing continuous and substantial changes. Initially pacing had an exclusively palliative role, since it was reserved for patients developing complete heart block or severe symptomatic bradycardia. With the appearance of novel pacing indications such as pacing for heart failure and atrial fibrillation, the effect of pacing site on cardiac function has become a critically important issue and a subject for consideration. It seems that the classical pacing site in the right ventricular apex is no longer the gold standard because of possible disadvantageous effects on cardiac function. The aim of this review article is to discuss the effect of right ventricular apical pacing on cardiac function including cellular and hemodynamic changes. We also aim to discuss the role of alternative pacing sites in the light of cardiac function.     

Permanent parahisian pacing

Right Ventricular Apical permanent pacing could have negative hemodynamic effects. A physiologic pacing modality should preserve a correct atrio-ventricular and interventricular synchronization. This can be obtained through biventricular pacing, left ventricular pacing, or from alternative right ventricular pacing sites. Direct His Bundle Pacing (DHBP) was documented as reliable and effective for preventing the desynchronization and negative effects of right ventricular apical pacing. It is, however, a complex method that requires longer average implant times, cannot be carried out on all patients and presents high pacing thresholds. On the contrary, the parahisian pacing, with simpler feasibility and reliability criteria, seems to guarantee an early invasion of the His-Purkinje conduction system, with a physiological ventricular activation, very similar to the one that can be obtained with direct His bundle pacing. We present our experience on 68 patients who underwent a permanent right ventricular pacing in hisian/parahisian region, for advanced AV block and narrow QRS. In the first 17 patients we performed a double-blind randomized controlled study, with two 6-months cross-over periods in parahisian and apical pacing, documenting a significant improvement of NYHA class, exercise tolerance, quality of life score, mitral and tricuspidal regurgitation degree, and interventricular mechanical delay. In the subsequent 51 patients, in a mean follow of 21 months/patient, the pacing threshold remained stable (0.7+/-0.5 V implant; 0.9+/-0.7 V follow-up; p=0.08). The ejection fraction maintained medium-long term stable values, confirming the fact that the parahisian pacing can prevent deterioration of the left ventricular function. Parahisian pacing, therefore, has proven to be a reliable method, easy to apply and effective in preventing the negative effects induced by non-physiological right ventricular apical pacing.     

The Effects Of Short Time Right Ventricular Pacing On Left Atrial Mechanical Functions

Objectives

Left atrium (LA) plays an important role in left ventricular filling. It is well known that right ventricular apical pacing has unfavorable effects on ventricular systolic and diastolic performance. The aim of this study is to evaluate the LA mechanical functions with 2D echocardiography in patients with a permanent pacemaker after short time ventricular pacing.

Design

Echocardiographic examination was performed in 38 patients (mean age 63.0± 10.9, 18 female) with dual chamber pacemakers or defibrillators (< 20% ventricular pacing within previous 6 months, all of them on sinus rhythm) before and after 4 hours > 90% ventricular pacing at 70 beats per minute in DDD mode with an optimal AV interval. Left atrial volumes (LAV) including at the time of mitral valve opening (Vmax), at closure (Vmin), and at the onset of atrial systole (Volp) were measured. The passive emptying, conduit, active emptying and total emptying volume, stroke volumes were also calculated.

Results

No significant differences were noted at baseline and after pacing for absolute Vmax, Volp, passive emptying, conduit, active emptying, total emptying volumes as well as the volumes indexed to body surface area (p >0.05).

Conclusions

Short - time RV pacing seems to have no acute effects on left atrial mechanical functions.     

Selective left bundle branch pacing for pediatric complete heart block

Traditionally Right Ventricle has been the preferred site of pacing for the management of symptomatic brady-arrhythmias. The deleterious effect of chronic RV pacing has been shown by several studies. This has generated interest into a novel pacing strategy called physiological pacing wherein the His bundle or the left bundle is paced directly with 4.1 F pacing lead. Herewith we are reporting a case of congenital complete heart block in a 13-year-old child for whom selective left bundle branch pacing was done. This physiological pacing will ensure a synchronized contraction of the ventricles thereby avoiding the deleterious effect of RV pacing.     

Ventricular pump function under ectopic excitation of the frog heart

The ventricular pump function under ectopic excitation of the heart was studied in decapitated and pithed adult frogs Rana temporaria (n = 21) at 18-19 degrees C. The intraventricular pressure was recorded with a catheter via ventricular wall. During pacing of the ventricular base and apex, the systolic pressure decreased (6.1 +/- 4.5 mm Hg and 8.9 +/- 5.0 mm Hg, respectively) as compared to the supraventricular rhythm (8.9 +/- 5.0 mm Hg, p < 0.05). The end-diastolic pressure decreased insignificantly both under basal and apical pacing. The systolic rate of pressure rise during dP/dtmax decreased under ventricular pacing, especially during pacing of the ventricular apex, as compared to the supraventricular rhythm (14.4 +/- 6/9 mm Hg/s and 22.1 +/- 11.2 mm Hg/s, respectively, p < 0.003). The isovolumetric relaxation (dP/dtmin) slowed during apical pacing as compared to the supraventricular rhythm (-25.1 +/- 13.6 and -35.6 +/- 18.3 mm Hg/s, respectively, p < 0.03). Ectopic excitation of the ventricular base and apex resulted in increase of the QRS duration (93 +/- 33 ms and 81 +/- 30 ms, respectively) as compared to the supraventricular rhythm (63 +/- 13 ms, p < 0.05). Thus, pacing of different ventricular areas ventricular myocardium with the ventricular pump function being reduced more obviously during the apical pacing compared to the pacing of ventricular base.     

Single-beat noninvasive imaging of ventricular endocardial and epicardial activation in patients undergoing CRT

Background

Little is known about the effect of cardiac resynchronization therapy (CRT) on endo- and epicardial ventricular activation. Noninvasive imaging of cardiac electrophysiology (NICE) is a novel imaging tool for visualization of both epi- and endocardial ventricular electrical activation.

Methodology/Principal Findings

NICE was performed in ten patients with congestive heart failure (CHF) undergoing CRT and in ten patients without structural heart disease (control group). NICE is a fusion of data from high-resolution ECG mapping with a model of the patient''s individual cardiothoracic anatomy created from magnetic resonance imaging. Beat-to-beat endocardial and epicardial ventricular activation sequences were computed during native rhythm as well as during ventricular pacing using a bidomain theory-based heart model to solve the related inverse problem. During right ventricular (RV) pacing control patients showed a deterioration of the ventricular activation sequence similar to the intrinsic activation pattern of CHF patients. Left ventricular propagation velocities were significantly decreased in CHF patients as compared to the control group (1.6±0.4 versus 2.1±0.5 m/sec; p<0.05). CHF patients showed right-to-left septal activation with the latest activation epicardially in the lateral wall of the left ventricle. Biventricular pacing resulted in a resynchronization of the ventricular activation sequence and in a marked decrease of total LV activation duration as compared to intrinsic conduction and RV pacing (129±16 versus 157±28 and 173±25 ms; both p<0.05).

Conclusions/Significance

Endocardial and epicardial ventricular activation can be visualized noninvasively by NICE. Identification of individual ventricular activation properties may help identify responders to CRT and to further improve response to CRT by facilitating a patient-specific lead placement and device programming.     

Initial experience of a cohort of patients with hypertrophic cardiomyopathy undergoing biventricular pacing

Background

Dual chamber pacing improves functional status and reduces left ventricular outflow tract gradients in some, but not all patients with hypertrophic cardiomyopathy (HCM) by altering ventricular depolarisation. We investigated the use of biventricular (BIV) pacing in symptomatic patients with HCM.

Method

8 patients aged 58±7yrs with symptomatic HCM underwent BIV pacing. 5 patients had LVOT gradients >30mmHg. Ventricular electrodes were placed in the right ventricle (RV) and a branch of the coronary sinus. An atrial electrode was inserted to achieve BIV pacing with a short AV delay. The short-term effects of different pacing modalities were assessed using 2-D and Doppler echocardiography. Symptoms and exercise tolerance were assessed after a month of each pacing mode. Long-term follow up data was available for 5 years.

Results

Baseline EF was 67±14% and mean QRS duration was 132±26msecs. BIV pacing reduced QRS duration compared to RV pacing (129±46 vs. 205±54msecs, p<0.005). Five of the seven patients had baseline LVOT gradients (mean 67±25mmHg) that decreased to 41±15mm Hg with RV pacing (p<0.01) and 25±15mmHg with BIV pacing (p<0.005). Improvements in exercise time with active pacing occurred in six out of eight patients (75%), three (37.5%) had optimal exercise times with RV pacing and three with BIV pacing. Of the three patients with short term improvements with BIV pacing, one died 4 years post implant, one deteriorated with LV dilatation and one had the system explanted for infection.

Conclusion

BIV pacing showed short-term beneficial effects in some patients over and above RV pacing alone.     

Left ventricular systolic torsion correlates global cardiac performance during dyssynchrony and cardiac resynchronization therapy

Left ventricular (LV) systolic torsion is a primary mechanism contributing to stroke volume (SV). We hypothesized that change in LV torsion parallels changes in global systolic performance during dyssynchrony and cardiac resynchronization therapy (CRT). Seven anesthetized open chest dogs had LV pressure-volume relationship. Apical, basal, and mid-LV cross-sectional echocardiographic images were studied by speckle tracking analysis. Right atrial (RA) pacing served as control. Right ventricular (RV) pacing simulated left bundle branch block. Simultaneous RV-LV free wall and RV-LV apex pacing (CRTfw and CRTa, respectively) modeled CRT. Dyssynchrony was defined as the time difference in peak strain between earliest and latest segments. Torsion was calculated as the maximum difference between the apical and basal rotation. RA pacing had minimal dyssynchrony (52 ± 36 ms). RV pacing induced dyssynchrony (189 ± 61 ms, P < 0.05). CRTa decreased dyssynchrony (46 ± 36 ms, P < 0.05 vs. RV pacing), whereas CRTfw did not (110 ± 96 ms). Torsion during baseline RA was 6.6 ± 3.7°. RV pacing decreased torsion (5.1 ± 3.6°, P < 0.05 vs. control), and reduced SV, stroke work (SW), and dP/dt(max) compared with RA (21 ± 5 vs. 17 ± 5 ml, 252 ± 61 vs. 151 ± 64 mJ, and 2,063 ± 456 vs. 1,603 ± 424 mmHg/s, respectively, P < 0.05). CRTa improved torsion, SV, SW, and dP/dt(max) compared with RV pacing (7.7 ± 4.7°, 23 ± 3 ml, 240 ± 50 mJ, and 1,947 ± 647 mmHg/s, respectively, P < 0.05), whereas CRTfw did not (5.1 ± 3.6°, 18 ± 5 ml, 175 ± 48 mJ, and 1,699 ± 432 mmHg/s, respectively, P < 0.05). LV torsion changes covaried across conditions with SW (y = 0.94x+12.27, r = 0.81, P < 0.0001) and SV (y = 0.66x+0.91, r = 0.81, P < 0.0001). LV dyssynchrony changes did not correlate with SW or SV (r = -0.12, P = 0.61 and r = 0.08, P = 0.73, respectively). Thus, we conclude that LV torsion is primarily altered by dyssynchrony, and CRT that restores LV performance also restores torsion.     

Normalisation of the ECG in a patient with right bundle branch block by cardiac pacing

Right ventricular apical pacing (RVA) appears to have potential deleterious effects on myocardial systolic and diastolic left ventricular function, especially in patients with intact AV conduction. Therefore, new pacing sites in the right ventricle are being explored to overcome these detrimental effects. Alternative pacing sites in the right ventricle are the right ventricular outflow tract (RVOT) and the right ventricular septum (RVS). In this case report, we demonstrate an exceptional form of ventricular fusion, namely normalisation of the QRS complex in a patient with pre-existing right bundle branch block by RVS pacing. To our knowledge, this is the first report in the literature where right ventricular pacing could restore a complete RBBB to a normal QRS complex by stimulating distally from the anatomical position of the RBBB, due to fusion between artificial right ventricular stimulation and intrinsic conduction over the left bundle of the specific His-Purkinje system.     

QRS alternans during right ventricular pacing while ablating a concealed left sided accessory pathway

A 16-year-old boy was referred for an electrophysiological study for documented regular narrow complex tachycardia. A diagnosis of a concealed left lateral accessory pathway was made with an eccentric atrial activation sequence both during tachycardia and right ventricular (RV) pacing. The pathway was mapped at the left posterior mitral vestibule during RV pacing, performed through the distal tip of the His bundle catheter pushed into right ventricular outflow tract. An unusual response to ventricular stimulation with alternation of QRS complex width and morphology was noted. The possible mechanisms are hereby discussed.     

Right bundle branch block pattern after uncomplicated right ventricular outflow tract pacing in a patient with a left sided superior vena cava and corrected tetralogy of Fallot

Usually an electrocardiogram after right ventricular (RV) pacing should yield left bundle branch block (LBBB) pattern. However, the presence of right bundle branch block (RBBB) pattern after pacemaker implantation should alert the physician to a malposition of lead. We report a case of 18-year-old female who underwent dual chamber pacemaker implantation and had RBBB pattern post implantation. Detailed evaluation revealed an uncomplicated right ventricular outflow tract pacing. The possible causes of this abnormal pattern after an uncomplicated RV pacing are also reviewed.     

Selective His-bundle pacing in an adult with atrioventricular canal defect via retrograde His localization

Adult congenital heart disease patients may undergo numerous fluoroscopically guided procedures including pacemaker implantation during their lifetime. One alternative to traditional pacemaker setup which may improve long-term pacing outcomes is His bundle pacing. Given the altered His-bundle location, and given increased radiation exposure over a lifetime, we used 3-dimensional mapping to locate the His and to minimize fluoroscopy for placement of a His-bundle pacemaker system in a 31-year old patient with atrioventricular canal defect and complete heart block with 100% RV pacing and epicardial lead fracture.MethodsAn Octapolar Livewire catheter (Abbott, Minneapolis, USA) was used for mapping and location of the His bundle from a right femoral venous access on the EnSite Precision system 3-dimensional mapping system (Abbott Medical, Abbott Park, IL). The same map was used to guide 3830 lead placement into the posterior-inferior His-bundle position.ResultsSuccessful placement of a His-bundle pacing system with thresholds of 1Volt@0.4ms for both the atrial and ventricular leads with selective His-bundle pacing noted. Ten-month follow-up demonstrated His-bundle capture at 0.75V@0.4ms with stable impedance, sensing and with 100% right ventricular pacing a projected longevity of 12 years total.ConclusionsSuccessful placement of selective His-bundle pacing can be achieved in an adult patient with atrioventricular canal defect using 3-dimensional mapping.     

Correlation of pacing site in right ventricle with paced QRS complex duration

Background

Pacing from RV mid septum and outflow tract septum has been proposed as a more physiological site of pacing and narrower paced QRS complex duration. The paced QRS morphology and duration in different RV pacing sites is under continued discussion. Hence, this study was designed to address the correlation of pacing sites in right ventricle with paced QRS complex duration.