Andreu Porta-Sánchez

Effects of Renal Artery Denervation on Ventricular Arrhythmias in a Postinfarct Model

Background— The therapeutic potential of renal denervation (RDN) for arrhythmias has not been fully explored. Detailed mechanistic evaluation is in order. The objective of the present study was to determine the antiarrhythmic potential of RDN in a postinfarct animal model and to determine whether any benefits relate to RDN-induced reduction of sympathetic effectors on the myocardium. Methods and Results— Pigs implanted with single-chamber implantable cardioverter defibrillators to record ventricular arrhythmias (VAs) were subjected to percutaneous coronary occlusion to induce myocardial infarction. Two weeks later, a sham or real RDN treatment was performed bilaterally using the St Jude EnligHTN basket catheter. Parameters of ventricular remodeling and modulation of cardio–renal sympathetic axis were monitored for 3 weeks after myocardial infarction. Histological analysis of renal arteries yielded a mean neurofilament score of healthy nerves that was significantly lower in the real RDN group than in sham controls; damaged nerves were found only in the real RDN group. There was a 100% reduction in the rate of spontaneous VAs after real RDN and a 75% increase in the rate of spontaneous VAs after sham RDN (P=0.03). In the infarcted myocardium, presence of sympathetic nerves and tissue abundance of neuropeptide-Y, an indicator of sympathetic nerve activities, were significantly lower in the RDN group. Peak and mean sinus tachycardia rates were significantly reduced after RDN. Conclusions— RDN in the infarcted pig model leads to reduction of postinfarction VAs and myocardial sympathetic effectors. This may form the basis for a potential therapeutic role of RDN in postinfarct VAs.

Mortality Implications of Appropriate Implantable Cardioverter Defibrillator Therapy in Secondary Prevention Patients: Contrasting Mortality in Primary Prevention Patients From a Prospective Population‐Based Registry

Background We sought to examine the mortality impact of appropriate implantable cardioverter defibrillator (ICD) therapy between patients who received ICD for primary versus secondary prevention purposes. Methods and Results From a prospective, population‐based registry, we identified 7020 patients who underwent de novo ICD implantation between February 2007 and May 2012 in Ontario, Canada. The primary outcome was all‐cause mortality. We used multivariable Cox proportional hazard modeling to adjust for differences in baseline characteristics and analyzed the mortality impact of first appropriate ICD therapy (shock and antitachycardia pacing [ATP]) as a time‐varying covariate. There were 1929 (27.5%) patients who received ICDs for secondary prevention purposes. The median follow‐up period was 5.02 years. Compared with those with secondary prevention ICDs, patients with primary prevention ICDs had more medical comorbidities, and lower ejection fraction. Patients who experienced appropriate ICD shock or ATP had greater risk of death compared with those who did not, irrespective of implant indication. In the primary prevention group, the adjusted hazard ratios of death for appropriate shock and ATP were 2.00 (95% CI: 1.72–2.33) and 1.73 (95% CI: 1.52–1.97), respectively. In the secondary prevention group, the adjusted hazard ratios of death for appropriate ICD shock and ATP were 1.46 (95% CI: 1.20–1.77) and 1.38 (95% CI: 1.16–1.64), respectively. Conclusions Despite having a more favorable clinical profile, occurrence of appropriate ICD shock or ATP in patients with secondary prevention ICDs was associated with similar magnitudes of mortality risk as those with primary prevention ICDs. A heightened degree of care is warranted for all patients who experience appropriate ICD shock or ATP therapy.

Effect of spatial resolution and filtering on mapping cardiac fibrillation

BACKGROUND Endocardial mapping tools use variable interelectrode resolution, whereas body surface mapping tools use narrow bandpass filtering (BPF) to map fibrillatory mechanisms established by high-resolution optical imaging. OBJECTIVE The purpose of this study was to study the effect of resolution and BPF on the underlying mechanism being mapped. METHODS Hearts from 14 healthy New Zealand white rabbits were Langendorff perfused. We studied the effect of spatial resolution and BPF on the location and characterization of rotors by comparing phase singularities detected by high-resolution unfiltered optical maps and of fibrillating myocardium with decimated and filtered maps with simulated electrode spacing of 2, 5, and 8 mm. RESULTS As we decimated the maps with 2-mm, 5-mm, and 8-mm interelectrode spacing, the mean ( ± SD) number of rotors detected decreased from 10.2 ± 9.6, 1.6 ± 3.2, and 0.2 ± 0.5, respectively. Lowering the resolution led to synthesized pseudo-rotors that may be inappropriately identified. Applying a BPF led to fewer mean phase singularities detected (248 ± 207 vs 333 ± 130; P<.01), giving the appearance of pseudo-spatial stability measured as translation index (with BPF 3.6 ± 0.4 mm vs 4.0 ± 0.5 mm without BPF; P<.01) and pseudo-temporal stability with longer duration (70.0 ± 17.6 ms in BPF maps vs 44.1 ± 6.6 ms in unfiltered maps; P<.001) than true underlying fibrillating myocardium mapped. CONCLUSION Electrode resolution and BPF of electrograms can result in distortion of the underlying electrophysiology of fibrillation. Newer mapping techniques need to demonstrate sensitivity analysis to quantify the degree of distortion before clinical use to avoid inaccurate electrophysiologic interpretation.

Resolving Bipolar Electrogram Voltages During Atrial Fibrillation Using Omnipolar Mapping

Background: Low-voltage–guided substrate modification is an emerging strategy in atrial fibrillation (AF) ablation. A major limitation to contemporary bipolar electrogram (EGM) analysis in AF is the resultant lower peak-to-peak voltage (Vpp) from variations in wavefront direction relative to electrode orientation and from fractionation and collision events. We aim to compare bipole Vpp with novel omnipolar peak-to-peak voltages (Vmax) in sinus rhythm (SR) and AF. Methods and Results: A high-density fixed multielectrode plaque was placed on the epicardial surface of the left atrium in dogs. Horizontal and vertical orientation bipolar EGMs, followed by omnipolar EGMs, were obtained and compared in both SR and AF. Bipole orientation has significant impact on bipolar EGM voltages obtained during SR and AF. In SR, vertical values were on average 66±119% larger than horizontal (P=0.004). In AF, vertical values were on average 31±96% larger than horizontal (P=0.07). Omnipole Vmax values were 99.9±125% larger than both horizontal (99.9±125%; P<0.001) and vertical (41±78%; P<0.0001) in SR and larger than both horizontal (76±109%; P<0.001) and vertical (52±70%; P value <0.0001) in AF. Vector field analysis of AF wavefronts demonstrates that omnipolar EGMs can account for collision and fractionation and record EGM voltages unaffected by these events. Conclusions: Omnipolar EGMs can extract maximal voltages from AF signals which are not influenced by directional factors, collision or fractionation, compared with contemporary bipolar techniques.

Constrictive Pericarditis: Etiologic Spectrum, Patterns of Clinical Presentation, Prognostic Factors, and Long-term Follow-up

INTRODUCTION AND OBJECTIVES Some reports have described a change in the etiologic spectrum of constrictive pericarditis. In addition, data on the relationship between its clinical presentation and etiology are lacking. We sought to describe the etiologies of the disease, their relationship with its clinical presentation and surgical findings, and to identify predictors of poor outcome. METHODS We analyzed 140 consecutive patients who underwent surgery for constrictive pericarditis over a 34-year period in a single center. RESULTS The etiology was idiopathic in 76 patients (54%), acute idiopathic pericarditis in 24 patients (17%), tuberculous pericarditis in 15 patients (11%), purulent pericarditis in 10 patients (7%), and cardiac surgery, radiation and uremia in 5, 3 and 2 patients respectively (4%, 2% and 1%). Mean duration of symptoms before pericardiectomy was 19 months (standard deviation, 44 months), the most acute presentation being for purulent pericarditis (26 days [range, 7-60 days]) and the most chronic for idiopathic cases (29 months [range, 4 days-360 months]). Perioperative mortality was 11%. There was no difference in mortality between etiologies. Median follow-up was 12 years (range, 0.1-33.0 years) in which 50 patients died. In a Cox-regression analysis, age at surgery, advanced New York Heart Association functional class (III to IV) and previous acute idiopathic pericarditis were associated with increased mortality during follow-up. CONCLUSIONS Most cases of constrictive pericarditis are idiopathic. Cardiac surgery and radiation accounted for a minority of cases. Etiologic investigations are warranted only in acute or subacute presentations. Age, advanced functional class, and previous acute idiopathic pericarditis are associated with increased mortality.

The effect of left ventricular pacing on transmural activation delay in myopathic human hearts

Aims Left ventricular (LV) epicardial pacing (LVEpiP) in human myopathic hearts does not decrease global epicardial activation delay compared with right ventricular (RV) endocardial pacing (RVEndoP); however, the effect on transmural activation delay has not been evaluated. To characterize the transmural electrical activation delay in human myopathic hearts during RVEndoP and LVEpiP compared with global epicardial activation delay. Methods and results Explanted hearts from seven patients (5 male, 46 ± 10 years) undergoing cardiac transplantation were Langendorff-perfused and mapped using an epicardial sock electrode array (112 electrodes) and 25 transmural plunge needles (four electrodes, 2 mm spacing), for a total of 100 unipolar transmural electrodes. Electrograms were recorded during LVEpiP and RVEndoP, and epicardial (sock) and transmural (needle) activation times, along with patterns of activation, were compared. There was no difference between the global epicardial activation times (LVEpiP 147 ± 8 ms vs. RVEndoP 156 ± 17 ms, P = 0.46). The mean LV transmural activation time during LVEpiP was significantly shorter than that during RVEndoP (125 ± 44 vs. 172 ± 43 ms, P < 0.001). During LVEpiP, of the transmural layers endo-, mid-myocardium and epicardium, LV endocardial layer was often the earliest compared with other transmural layers. Conclusion In myopathic human hearts, LVEpiP did not decrease global epicardial activation delays compared with RVEndoP. LV epicardial pacing led to early activation of the LV endocardium, revealing the importance of the LV endocardium even when pacing from the LV epicardium.

Incidence, Diagnosis, and Management of QT Prolongation Induced by Cancer Therapies: A Systematic Review

Background The cardiovascular complications of cancer therapeutics are the focus of the burgeoning field of cardio‐oncology. A common challenge in this field is the impact of cancer drugs on cardiac repolarization (ie, QT prolongation) and the potential risk for the life‐threatening arrhythmia torsades de pointes. Although QT prolongation is not a perfect marker of arrhythmia risk, this has become a primary safety metric among oncologists. Cardiologists caring for patients receiving cancer treatment should become familiar with the drugs associated with QT prolongation, its incidence, and appropriate management strategies to provide meaningful consultation in this complex clinical scenario. Methods and Results In this article, we performed a systematic review (using Preferred Reporting Items of Systematic Reviews and Meta‐Analyses (PRISMA) guidelines) of commonly used cancer drugs to determine the incidence of QT prolongation and clinically relevant arrhythmias. We calculated summary estimates of the incidence of all and clinically relevant QT prolongation as well as arrhythmias and sudden cardiac death. We then describe strategies to prevent, identify, and manage QT prolongation in patients receiving cancer therapy. We identified a total of 173 relevant publications. The weighted incidence of any corrected QT (QTc) prolongation in our systematic review in patients treated with conventional therapies (eg, anthracyclines) ranged from 0% to 22%, although QTc >500 ms, arrhythmias, or sudden cardiac death was extremely rare. The risk of QTc prolongation with targeted therapies (eg, small molecular tyrosine kinase inhibitors) ranged between 0% and 22.7% with severe prolongation (QTc >500 ms) reported in 0% to 5.2% of the patients. Arrhythmias and sudden cardiac death were rare. Conclusions Our systematic review demonstrates that there is variability in the incidence of QTc prolongation of various cancer drugs; however, the clinical consequence, as defined by arrhythmias or sudden cardiac death, remains rare.

Comparison of Electrocardiographic Characteristics in Men Versus Women ≤ 55 Years With Acute Myocardial Infarction (a Variation in Recovery: Role of Gender on Outcomes of Young Acute Myocardial Infarction Patients Substudy)

Young women with acute myocardial infarction (AMI) have a worse prognosis than their male counterparts. We searched for differences in the electrocardiographic presentation of men and women in a large, contemporary registry of young adults with AMI that could help explain gender differences in outcomes. The qualifying electrocardiogram was blindly assessed by a central core lab in 3,354 patients (67% women) aged 18 to 55 years included in the Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients study. Compared with men, women did not have a different frequency of sinus rhythm, and they had shorter PR and QRS intervals and longer QTc intervals. Intraventricular conduction disturbances were not different among genders. Notably, women were more likely than men to have abnormal Q waves in anterior leads and a lower frequency of Q waves in other territories. ST-segment elevation myocardial infarction (STEMI) diagnosis was less frequent in women than in men (44.6% vs 55.1%, p < 0.001). Among patients with STEMI, women had less magnitude and extent of ST-segment elevation than men. In patients with non-STEMI, the frequency, magnitude, and extent of ST-segment depression were not different among genders, but women had anterior ST-segment depression less frequently and anterior negative T waves more frequently compared with men. These differences remained statistically significant after adjusting for baseline characteristics. In conclusion, there are significant gender differences in the electrocardiographic presentation of AMI among young patients. Further studies are warranted to evaluate their impact on gender-related differences in the management and outcomes of AMI.

Transbaffle multielectrode mapping of atrial flutter post double switch operation.

A 26-year-old woman with congenitally corrected transposition of the great arteries (ccTGA) had undergone a doubleswitch corrective surgery consisting of a Mustard procedure (bovine pericardial baffles and hemashield grafts) and arterial switch (Jatene technique). She subsequently developed drug refractory atrial flutter and underwent ablation. An Agilis sheath (St. Jude Medical, St. Paul, MN, USA) and a long BRK 1 needle were used for the transbaffle puncture guided by transoesophageal echocardiography. Activation maps of the systemic venous antrum (SVA) and then the PVA (Fig. 1A) were created with a 20-pole PentaRay R

Reduced T wave alternans in heart failure responders to cardiac resynchronization therapy: Evidence of electrical remodeling

Background T-wave alternans (TWA), a marker of electrical instability, can be modulated by cardiac resynchronization therapy (CRT). The relationship between TWA and heart failure response to CRT has not been clearly defined. Methods and results In 40-patients (age 65±11 years, left ventricular ejection-fraction [LVEF] 23±7%), TWA was evaluated prospectively at median of 2 months (baseline) and 8 months (follow-up) post-CRT implant. TWA-magnitude (Valt >0μV, k≥3), its duration (d), and burden (Valt ·d) were quantified in moving 128-beat segments during incremental atrial (AAI, native-TWA) and atrio-biventricular (DDD-CRT) pacing. The immediate and long-term effect of CRT on TWA was examined. Clinical response to CRT was defined as an increase in LVEF of ≥5%. Native-TWA was clinically significant (Valt ≥1.9μV, k≥3) in 68% of subjects at baseline. Compared to native-TWA at baseline, DDD-CRT pacing at baseline and follow-up reduced the number of positive TWA segments, peak-magnitude, longest-duration and peak-burden of TWA (44±5 to 33±5 to 28±4%, p = 0.02 and 0.002; 5.9±0.8 to 4.1±0.7 to 3.8±0.7μV, p = 0.01 and 0.01; 97±9 to 76±8 to 67±8sec, p = 0.004 and <0.001; and 334±65 to 178±58 to 146±54μV.sec, p = 0.01 and 0.004). In addition, the number of positive segments and longest-duration of native-TWA diminished during follow-up (44±5 to 35±6%, p = 0.044; and 97±9 to 81±9sec, p = 0.02). Clinical response to CRT was observed in 71% of patients; the reduction in DDD-CRT paced TWA both at baseline and follow-up was present only in responders (interaction p-values <0.1). Conclusion Long-term CRT reduces the prevalence and magnitude of TWA. This CRT induced beneficial electrical remodeling is a marker of clinical response after CRT.