[New frontiers in pacing: from myocardial pacing to conduction system pacing]. / Nuove frontiere dell'elettrostimolazione: dal pacing del miocardio comune al pacing del sistema di conduzione.

For many years, cardiac pacing has been based on the stimulation of right ventricular common myocardium to correct diseases of the conduction system. The birth and the development of cardiac resynchronization have led to growing interest in the correction and prevention of pacing-induced dyssynchrony. Many observational studies and some randomized clinical trials have shown that conduction system pacing (CSP) can not only prevent pacing-induced dyssynchrony but can also correct proximal conduction system blocks, with reduction of QRS duration and with equal or greater effectiveness than biventricular pacing. Based on these results, many Italian electrophysiologists have changed the stimulation target from the right ventricular common myocardium to CSP. The two techniques with greater clinical impact are the His bundle stimulation and the left bundle branch pacing. The latter, in particular, because of its easier implantation technique and better electric parameters, is spreading like wildfire and is representing a real revolution in the cardiac pacing field. However, despite the growing amount of data, until now, the European Society of Cardiology guidelines give a very limited role to CSP.

Determination of sensed and paced atrial-ventricular delay in cardiac resynchronization therapy.

BACKGROUND: Optimization of atrial-ventricular delay (AVD) during atrial sensing (SAVD) and pacing (PAVD) provides the most effective cardiac resynchronization therapy (CRT). We demonstrate a novel electrocardiographic methodology for quantifying electrical synchrony and optimizing SAVD/PAVD. METHODS: We studied 40 CRT patients with LV activation delay. Atrial-sensed to RV-sensed (As-RVs) and atrial-paced to RV-sensed (Ap-RVs) intervals were measured from intracardiac electrograms (IEGM). LV-only pacing was performed over a range of SAVD/PAVD settings. Electrical dyssynchrony (cardiac resynchronization index; CRI) was measured at each setting using a multilead ECG system placed over the anterior and posterior torso. Biventricular pacing, which included multiple interventricular delays, was also conducted in a subset of 10 patients. RESULTS: When paced LV-only, peak CRI was similar (93 ± 5% vs. 92 ± 5%) during atrial sensing or pacing but optimal PAVD was 61 ± 31 ms greater than optimal SAVD. The difference between As-RVs and Ap-RVs intervals on IEGMs (62 ± 31 ms) was nearly identical. The slope of the correlation line (0.98) and the correlation coefficient r (0.99) comparing the 2 methods of assessing SAVD-PAVD offset were nearly 1 and the y-intercept (0.63 ms) was near 0. During simultaneous biventricular (BiV) pacing at short AVD, SAVD and PAVD programming did not affect CRI, but CRI was significantly (p < .05) lower during atrial sensing at long AVD. CONCLUSIONS: A novel methodology for measuring electrical dyssynchrony was used to determine electrically optimal SAVD/PAVD during LV-only pacing. When BiV pacing, shorter AVDs produce better electrical synchrony.

Cardiac implantable electronic devices and bloodstream infections: management and outcomes.

BACKGROUND AND AIMS: Bloodstream infection (BSI) of any cause may lead to device infection in cardiac implantable electronic device (CIED) patients. Aiming for a better understanding of the diagnostic approach, treatment, and outcome, patients with an implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy and defibrillator (CRT-D) hospitalized with BSI were investigated. METHODS: This is a single-centre, retrospective, cohort analysis including consecutive ICD/CRT-D patients implanted between 2012 and 2021. These patients were screened against a list of all hospitalized patients having positive blood cultures consistent with diagnosed infection in any department of a local public hospital. RESULTS: The total cohort consisted of 515 patients. Over a median follow-up of 59 months (interquartile range 31-87 months), there were 47 BSI episodes in 36 patients. The majority of patients with BSI (92%) was admitted to non-cardiology units, and in 25 episodes (53%), no cardiac imaging was performed. Nearly all patients (85%) were treated with short-term antibiotics, whereas chronic antibiotic suppression therapy (n = 4) and system extraction (n = 3) were less frequent. Patients with BSI had a nearly seven-fold higher rate (hazard ratio 6.7, 95% confidence interval 3.9-11.2; P < .001) of all-cause mortality. CONCLUSIONS: Diagnostic workup of defibrillator patients with BSI admitted to a non-cardiology unit is often insufficient to characterize lead-related endocarditis. The high mortality rate in these patients with BSI may relate to underdiagnosis and consequently late/absence of system removal. Efforts to increase an interdisciplinary approach and greater use of cardiac imaging are necessary for timely diagnosis and adequate treatment.

Redefining left bundle branch block from high-density electroanatomical mapping.

BACKGROUND: The existing ECG criteria for diagnosing left bundle branch block (LBBB) are insufficient to distinguish between true and false blocks accurately. METHODS: We hypothesized that the notch width of the QRS complex in the lateral leads (I, avL, V5, V6) on the LBBB-like ECG could further confirm the diagnosis of true complete left bundle branch block (t-LBBB). We conducted high-density, three-dimensional electroanatomical mapping in the cardiac chambers of 37 patients scheduled to undergo CRT. These patients' preoperative electrocardiograms met the ACC/AHA/HRS guidelines for the diagnosis of complete LBBB. If the left bundle branch potential could be mapped from the base of the heart to the apex on the left ventricular septum, it was defined as a false complete left bundle branch block (f-LBBB). Otherwise, it was categorized as a t-LBBB. We conducted a comparative analysis between the two groups, considering the clinical characteristics, real-time correspondence between the spread of ventricular electrical excitation and the QRS wave, QRS notch width of the lateral leads (I, avL, V5, V6), and the notch width/left ventricular end-diastolic diameter (Nw/LVd) ratio. We performed the ROC correlation analysis of Nw/LVd and t-LBBB to determine the sensitivity and specificity for diagnostic authenticity. RESULTS: Twenty-five patients were included in the t-LBBB group, while 12 patients were assigned to the f-LBBB group. Within the t-LBBB group, the first peak of the QRS notch correlated with the depolarization of the right ventricle and septum, the trough corresponded to the depolarization of the left ventricle across the left ventricle, and the second peak aligned with the depolarization of the left ventricular free wall. In contrast, within the f-LBBB group, the first peak coincided with the depolarization of the right ventricle and a majority of the left ventricle, the second peak occurred due to the depolarization of the latest, locally-activated myocardium in the left ventricle, and the trough was a result of delayed activation of the left ventricle that did not align with the usual peak timing. The QRS notch width (45.2 ± 12.3 ms vs. 52.5 ± 9.2 ms, P < 0.05) and the Nw/LVd ratio (0.65 ± 0.19 ms/mm vs. 0.81 ± 0.17 ms/mm, P < 0.05) were compared between the two groups. After conducting the ROC correlation analysis, a sensitivity of 56% and a specificity of 91.7% for diagnosing t-LBBB using Nw/LVd were obtained. CONCLUSION: By utilizing the current diagnostic criteria for LBBB, an increased Nw/LVd value can enhance the effectiveness of diagnosing LBBB.

Monolithic silicon for high spatiotemporal translational photostimulation.

Electrode-based electrical stimulation underpins several clinical bioelectronic devices, including deep-brain stimulators1,2 and cardiac pacemakers3. However, leadless multisite stimulation is constrained by the technical difficulties and spatial-access limitations of electrode arrays. Optogenetics offers optically controlled random access with high spatiotemporal capabilities, but clinical translation poses challenges4-6. Here we show tunable spatiotemporal photostimulation of cardiac systems using a non-genetic platform based on semiconductor-enabled biomodulation interfaces. Through spatiotemporal profiling of photoelectrochemical currents, we assess the magnitude, precision, accuracy and resolution of photostimulation in four leadless silicon-based monolithic photoelectrochemical devices. We demonstrate the optoelectronic capabilities of the devices through optical overdrive pacing of cultured cardiomyocytes (CMs) targeting several regions and spatial extents, isolated rat hearts in a Langendorff apparatus, in vivo rat hearts in an ischaemia model and an in vivo mouse heart model with transthoracic optical pacing. We also perform the first, to our knowledge, optical override pacing and multisite pacing of a pig heart in vivo. Our systems are readily adaptable for minimally invasive clinical procedures using our custom endoscopic delivery device, with which we demonstrate closed-thoracic operations and endoscopic optical stimulation. Our results indicate the clinical potential of the leadless, lightweight and multisite photostimulation platform as a pacemaker in cardiac resynchronization therapy (CRT), in which lead-placement complications are common.

Association between QRS shortening and mortality after cardiac resynchronization therapy: Results from the DANISH study.

BACKGROUND: Changes in QRS duration (∆QRS) are often used in the clinical setting to evaluate the effect of cardiac resynchronization therapy (CRT), although an association between ∆QRS and outcomes is not firmly established. We aimed to assess the association between mortality and ∆QRS after CRT in patients from the DANISH (Danish Study to Assess the Efficacy of ICDs in Patients with Non-Ischemic Systolic Heart Failure on Mortality) study. METHODS: We included all patients from DANISH who received a CRT device and had available QRS duration data before and after implantation. Cox proportional hazards models were used to assess associations between ∆QRS (post-CRT QRS minus pre-CRT QRS) and mortality. RESULTS: Complete data were available in 572 patients. Median baseline QRS duration was 160 ms (IQR [146;180]). Post-CRT QRS was recorded a median of 48 days (IQR [33;86]) after implantation, and the median ∆QRS was -14 ms (IQR [-38;-3]). During a median follow-up of 4.1 years (IQR [2.5;5.8]), 106 patients died. In crude Cox regression, all-cause mortality was reduced by 6% per 10 ms shortening of QRS (HR 0.94; CI: 0.88-1.00, p = 0.04). The effect did not remain significant after multivariable adjustment (HR 1.01, CI: 0.93-1.10, p = 0.77). Further, no association was found between ∆QRS and improvement of New York Heart Association functional class at 6 months (OR 1.03, CI: 0.96-1.10, p = 0.42). CONCLUSION: In a large cohort of patients with non-ischemic cardiomyopathy, reduction of QRS duration after CRT was not associated with changes in mortality during long-term follow-up.

Motion correction of wide-detector 4DCT images for cardiac resynchronization therapy planning.

BACKGROUND: Lead placement at the latest mechanically activated left ventricle (LV) segments is strongly correlated with response to cardiac resynchronization therapy (CRT). We demonstrate the feasibility of a cardiac 4DCT motion correction algorithm (ResyncCT) in estimating LV mechanical activation for guiding lead placement in CRT. METHODS: Subjects with full cardiac cycle 4DCT images acquired using a wide-detector CT scanner for CRT planning/upgrade were included. 4DCT images exhibited motion artifact-induced false-dyssynchrony, hindering LV mechanical activation time estimation. Motion-corrupted images were processed with ResyncCT to yield motion-corrected images. Time to onset of shortening (TOS) was estimated in each of 72 endocardial segments. A false-dyssynchrony index (FDI) was used to quantify the extent of motion artifacts in the uncorrected and the ResyncCT images. After motion correction, the change in classification of LV free-wall segments as optimal target sites for lead placement was investigated. RESULTS: Twenty subjects (70.7 â€‹± â€‹13.9 years, 6 female) were analyzed. Motion artifacts in the ResyncCT-processed images were significantly reduced (FDI: 28.9 â€‹± â€‹9.3 â€‹% vs 47.0 â€‹± â€‹6.0 â€‹%, p â€‹< â€‹0.001). In 10 (50 â€‹%) subjects, ResyncCT motion correction yielded statistically different TOS estimates (p â€‹< â€‹0.05). Additionally, 43 â€‹% of LV free-wall segments were reclassified as optimal target sites for lead placement after motion correction. CONCLUSIONS: ResyncCT significantly reduced motion artifacts in wide-detector cardiac 4DCT images, yielded statistically different time to onset of shortening estimates, and changed the location of optimal target sites for lead placement. These results highlight the potential utility of ResyncCT motion correction in CRT planning when using wide-detector 4DCT imaging.

Utilization of and perceived need for simulators in clinical electrophysiology: results from an EHRA physician survey.

AIMS: Simulator training has been recently introduced in electrophysiology (EP) programmes in order to improve catheter manipulation skills without complication risks. The aim of this study is to survey the current use of EP simulators and the perceived need for these tools in clinical training and practice. METHODS AND RESULTS: A 20-item online questionnaire developed by the Scientific Initiatives Committee of the European Heart Rhythm Association (EHRA) in collaboration with EHRA Digital Committee was disseminated through the EHRA Scientific Research Network members, national EP groups, and social media platforms. Seventy-four respondents from 22 countries (73% males; 50% under 40 years old) completed the survey. Despite being perceived as useful among EP professionals (81%), EP simulators are rarely a part of the institutional cardiology training programme (20%) and only 18% of the respondents have an EP simulator at their institution. When available, simulators are mainly used in EP to train transseptal puncture, ablation, and mapping, followed by device implantation (cardiac resynchronization therapy [CRT], leadless, and conduction system pacing [CSP]). Almost all respondents (96%) believe that simulator programmes should be a part of the routine institutional EP training, hopefully developed by EHRA, in order to improve the efficacy and safety of EP procedures and in particular CSP 58%, CRT 42%, leadless pacing 38%, or complex arrhythmia ablations (VT 58%, PVI 45%, and PVC 42%). CONCLUSION: This current EHRA survey identified a perceived need but a lack of institutional simulator programme access for electrophysiologists who could benefit from it in order to speed up the learning curve process and reduce complications of complex EP procedures.

Clinical outcomes and predictors of delayed echocardiographic response to cardiac resynchronization therapy.

INTRODUCTION: The clinical outcomes and mechanisms of delayed responses to cardiac resynchronization therapy (CRT) remain unclear. We aimed to investigate the differences in outcomes and gain insight into the mechanisms of early and delayed responses to CRT. METHODS: This retrospective study included 110 patients who underwent CRT implantation. Positive response to CRT was defined as ≥15% reduction of left ventricular (LV) end-systolic volume on echocardiography at 1 year (early phase) and 3 years (delayed phase) after implantation. The latest mechanical activation site (LMAS) of the LV was identified using two-dimensional speckle-tracking radial strain analysis. RESULTS: Seventy-eight (71%) patients exhibited an early response 1 year after CRT implantation. Of 32 non-responders in the early phase, 12 (38%) demonstrated a delayed response, and 20 (62%) were classified as non-responders after 3 years. During the follow-up time of 10.3 ± 0.5 years, the delayed and early responders had a similar prognosis of mortality and heart failure (HF) hospitalization. In contrast, non-responders had a worse prognosis. Multivariate analysis revealed that a longer duration (months) between initial HF hospitalization and CRT (odds ratio [OR]: 1.126; 95% confidence interval [CI]: 1.036-1.222; p = .005), non-exact concordance of LV lead location with LMAS (OR: 32.744; 95% CI: 1.101-973.518; p = .044), and pre-QRS duration (OR: 0.901; 95% CI: 0.827-0.981; p = .016) were independent predictors of delayed response to CRT compared with early response. CONCLUSION: The prognoses were similar regardless of the response time after CRT. A longer history of HF, suboptimal LV lead position, and shorter pre-QRS duration were related to delayed response than early response.

Electrical therapies in heart failure: Evolving technologies and indications.

Device therapy for heart failure has rapidly evolved over 2 decades. The knowledge of indications, assessment lead and device technology has expanded to include CRT, leadless pacing and conduction system pacing such as His bundle and left bundle branch area pacing. But there is still a lack of evidence for these new technologies as well as for common indications such as atrial fibrillation and upgrading from a previous device. The role of personalized medicine will become increasingly important when selecting candidates for CRT, primary preventive ICD ablation procedures and emerging new devices such as cardiac contractility modulation (CCM). Rapidity of therapy is associated with outcome which will be a challenge. If properly implemented devices and drugs will have a large positive affect of HF outcomes.

Cardiac resynchronization using fusion pacing during exercise.

INTRODUCTION: Fusion pacing requires correct timing of left ventricular pacing to right ventricular activation, although it is unclear whether this is maintained when atrioventricular (AV) conduction changes during exercise. We used cardiopulmonary exercise testing (CPET) to compare cardiac resynchronization therapy (CRT) using fusion pacing or fixed AV delays (AVD). METHODS: Patients 6 months post-CRT implant with PR intervals < 250 ms performed two CPET tests, using either the SyncAV™ algorithm or fixed AVD of 120 ms in a double-blinded, randomized, crossover study. All other programming was optimized to produce the narrowest QRS duration (QRSd) possible. RESULTS: Twenty patients (11 male, age 71 [65-77] years) were recruited. Fixed AVD and fusion programming resulted in similar narrowing of QRSd from intrinsic rhythm at rest (p = .85). Overall, there was no difference in peak oxygen consumption (V̇O2 PEAK , p = .19), oxygen consumption at anaerobic threshold (VT1, p = .42), or in the time to reach either V̇O2 PEAK (p = .81) or VT1 (p = .39). The BORG rating of perceived exertion was similar between groups. CPET performance was also analyzed comparing whichever programming gave the narrowest QRSd at rest (119 [96-136] vs. 134 [119-142] ms, p < .01). QRSd during exercise (p = .03), peak O2 pulse (mL/beat, a surrogate of stroke volume, p = .03), and cardiac efficiency (watts/mL/kg/min, p = .04) were significantly improved. CONCLUSION: Fusion pacing is maintained during exercise without impairing exercise capacity compared with fixed AVD. However, using whichever algorithm gives the narrowest QRSd at rest is associated with a narrower QRSd during exercise, higher peak stroke volume, and improved cardiac efficiency.

Post-implantation CMR imaging to study biventricular pacing effects on the right ventricle in left bundle branch block patients.

Cardiac resynchronization therapy (CRT) is an established treatment for heart failure patients with left ventricular dysfunction and a left bundle branch block. However, its impact on right ventricular (RV) function remains uncertain. This cardiac magnetic resonance imaging study found that CRT did not improve RV volumes and function, and CRT-off during follow-up had an immediate detrimental effect on the RV, which may suggest potential unfavorable RV remodeling with RV pacing during CRT.

Outcomes of dual-chamber implantable cardioverter defibrillator for left bundle branch area pacing: A systematic review of literature.

OBJECTIVE: This systematic review of literature aimed to evaluate the safety and efficacy of dual-chamber ICDs for LBBAP in patients with left bundle branch block (LBBB). METHODS: Digital databases were searched systematically to identify studies reporting the left bundle branch area pacing (LBBAP) with implantable cardioverter defibrillator (ICD) placement in patients with LBBB. Detailed study and patient-level baseline characteristics including the type of study, sample size, follow-up, number of cases, age, gender, and baseline characteristics were abstracted. RESULTS: In a total of three studies, 34 patients were included in this review. There was a significant improvement reported in QRS duration in all studies. The mean QRS duration at baseline was 170 ± 17.4 ms, whereas the follow-up QRS duration at follow-up was 121 ± 17.3 ms. Two studies reported a significant improvement of 50% in LVEF from baseline. No lead-related complications or arrhythmic events were recorded in any study. The findings of the systematic review suggest that dual-chamber ICD for LBBAP is a promising intervention for patients with heart conditions. CONCLUSION: The procedure offers significant improvements in QRS duration and LVEF, and there were no lead-related complications or arrhythmic events recorded in any of the studies.

Emerging Technologies in Cardiac Pacing.

Cardiac pacing to treat bradyarrhythmias has evolved in recent decades. Recognition that a substantial proportion of pacemaker-dependent patients can develop heart failure due to electrical and mechanical dyssynchrony from traditional right ventricular apical pacing has led to development of more physiologic pacing methods that better mimic normal cardiac conduction and provide synchronized ventricular contraction. Conventional biventricular pacing has been shown to benefit patients with heart failure and conduction system disease but can be limited by scarring and fibrosis. His bundle pacing and left bundle branch area pacing are novel techniques that can provide more physiologic ventricular activation as an alternative to conventional or biventricular pacing. Leadless pacing has emerged as another alternative pacing technique to overcome limitations in conventional transvenous pacemaker systems. Our objective is to review the evolution of cardiac pacing and explore these new advances in pacing strategies.

Sex-Specific Outcomes of LBBAP Versus Biventricular Pacing: Results From I-CLAS.

BACKGROUND: Cardiac resynchronization therapy (CRT) using biventricular pacing (BVP) has been associated with greater clinical improvement in women than men. Recently, left bundle branch area pacing (LBBAP) has been shown to be an alternative form of CRT. OBJECTIVES: The purpose of this study was to investigate sex-specific outcomes for death and heart failure events in a large, international, multicenter, cohort of patients undergoing CRT with BVP or LBBAP. METHODS: In this international study of 1,778 patients (575 female and 1203 male), sex-specific survival analysis was performed to compare the effect of LBBAP-CRT relative to BVP-CRT on the combined endpoint of death or heart failure hospitalization (HFH), and secondary endpoints of HFH only, and death alone. RESULTS: Female patients were more likely to have nonischemic cardiomyopathy and left bundle branch block (LBBB) and less likely to have hypertension, diabetes, or coronary artery disease than were male patients. Overall, female patients had a better result with LBBAP compared with BVP than did male patients, with a significant 36% reduction in death or HFH (HR: 0.64; 95% CI: 0.43 to 0.97; P = 0.03) and a significant 60% reduction in HFH alone (HR: 0.4; 95% CI: 0.24 to 0.69, P < 0.01). Women had a greater reduction in death or HFH among those with nonischemic cardiomyopathy (HR: 0.45 95% CI: 0.26 to 0.79; P < 0.01) and LBBB (HR: 0.49; 95% CI: 0.27 to 0.87; P < 0.01). Sex-specific echocardiographic outcomes were better in women than in men. CONCLUSIONS: Women obtained significantly greater reductions in the combined endpoint of death or HFH (primarily driven by reduction in HFH) with LBBAP compared with BVP among patients requiring CRT than did men.

Left ventricular lead placement in cardiac resynchronization therapy: Current data and potential explanations for the lack of benefit.

The present article reviews the literature on image-guided cardiac resynchronization therapy (CRT) studies. Improved outcome to CRT has been associated with the placement of a left ventricular (LV) lead in the latest activated segment free from scar. The majority of randomized controlled trials investigating guided LV lead implantation did not show superiority over conventional implantation approaches. Several factors may contribute to this paradoxical observation, including inclusion criteria favoring patients with left bundle branch block who already respond well to conventional anatomical LV lead implantation, differences in activation wavefronts during simultaneous right ventricular and LV pacing, incorrect definition of target regions, and limitations in coronary venous anatomy that prevent access to target regions that are detected by imaging. It is imperative that exclusion of patients lacking access to target regions from these studies would lead to larger benefit of image-guided CRT.

Beyond biventricular pacing: Exploring the advantages of his-bundle pacing and left bundle branch pacing in heart failure-A systematic review and meta-analysis.

BACKGROUND: This meta-analysis compares His-Purkinje system pacing (HPSP), a novel cardiac resynchronization therapy (CRT) technique that targets the intrinsic conduction system of the heart, with conventional biventricular pacing (BiVP) in heart failure (HF) patients with left ventricular (LV) dysfunction and dyssynchrony. METHODS: We searched multiple databases up to May 2023 and identified 18 studies (five randomized controlled trials and 13 observational studies) involving 1291 patients. The outcome measures were QRS duration, left ventricular ejection fraction (LVEF) improvement, left ventricular end-diastolic diameter (LVEDD) change, HF hospitalization, and New York Heart Association (NYHA) functional class improvement. We used a random-effects model to calculate odds ratios (OR), and mean differences (MD) with 95% confidence intervals (CI). We also assessed the methodological quality of the studies. RESULTS: The mean LVEF was 30.7% and the mean follow-up duration was 8.1 months. Among LBBP, HBP, and BiVP, HBP provided the shortest QRS duration [MD: -18.84 ms, 95% CI: -28.74 to -8.94; p = 0.0002], while LBBP showed the greatest improvement in LVEF [MD: 5.74, 95% CI: 2.74 to 7.46; p < 0.0001], LVEDD [MD: -5.55 mm, 95% CI: -7.51 to -3.59; p < 0.00001], and NYHA functional class [MD: -0.58, 95% CI: -0.80 to --0.35; p < 0.00001]. However, there was no significant difference in HF hospitalization between HPSP and BiVP. CONCLUSION: LBBP as modality of HPSP demonstrated superior outcomes in achieving electrical ventricular synchrony and systolic function, as well as alleviating HF symptoms, compared to other pacing techniques.

Multimodality Imaging for Selecting Candidates for CRT: Do We Have a Single Alley to Increase Responders?

Cardiac resynchronization therapy has evolved in recent years to provide a reduction of morbidity and mortality for many patients with heart failure. Its application and optimization is an evolving field and its use requires a multidisciplinary approach for patient and device selection, technical preprocedural planning, and optimization. While echocardiography has always been considered the first line for the evaluation of patients, additional imaging techniques have gained increasing evidence in recent years. Today different details about heart anatomy, function, dissynchrony can be investigated by magnetic resonance, cardiac computed tomography, nuclear imaging, and more, with the aim of obtaining clues to reach a maximal response from the electrical therapy. The purpose of this review is to provide a practical analysis of the single and combined use of different imaging techniques in the preoperative and perioperative phases of cardiac resynchronization therapy, underlining their main advantages, limitations, and information provided.

Case of a misleading ECG.

An elderly man with severe chronic obstructive pulmonary disease and a history of complete heart block with pacemaker placement was found to have pacemaker lead infection and required device extraction. He had a standard dual chamber pacemaker in place, however the ECG obtained showed paced QRS complexes with presence of R wave in lead V1 and QS in lead I suggestive of left ventricular pacing. Additional imaging with CT scan obtained for confirmation revealed that the heart was displaced to the left posterior hemithorax secondary to pulmonary disease. Due to significant posterolateral rotation of the heart, a right ventricular paced rhythm can demonstrate Q/S waves in the lateral leads (I, aVL, V5-6) and R waves in the right precordial leads (V1-3). This can be misdiagnosed as a left ventricular paced rhythm.