Potential Role of Life Stress in Unexplained Sudden Cardiac Arrest.

BACKGROUND: The etiology of sudden cardiac arrest (SCA) in individuals without known cardiovascular heart disease remains elusive in nearly half of all patients after systematic testing. We investigated the relationship between stressful life events and SCA risk in cases of explained and unexplained SCA (USCA) events. METHODS: Individuals who previously experienced SCA were enrolled prospectively and divided into a USCA or explained SCA (ESCA) subgroup dependent on whether a diagnosis was ascribed after SCA. Participants completed either the 1997 Recent Life Changes Questionnaire, Student Stress Scale, or Social Re-adjustment Rating Scale for Non-Adults recalling events during the year preceding their SCA, depending on age at SCA presentation; all measure stress in life change units (LCUs). SCA group scores were compared with an age- and sex-matched control group. RESULTS: We compared 36 SCA group participants (22 USCA, 14 ESCA, age 47 ± 15 years, age at SCA 40 ± 14 years, 50% male) with 36 control participants (age 47 ± 15 years, 50% male). There was no significant difference in LCU score between the control group and the SCA group (248 ± 181 LCU vs 252 ± 227 LCU; P > .05). The ESCA subgroup had significantly lower mean LCU scores than the USCA subgroup (163 ± 183 LCU vs 308 ± 237 LCU; P = .030). CONCLUSIONS: Stressful life events, especially those producing chronic stress, might predispose otherwise healthy individuals to lethal arrhythmias. Further investigation into the role of stress in SCA precipitation is warranted.

CONTEXTE: La cause de l'arrêt cardiaque subit (ACS) chez les personnes n'ayant pas de maladie cardiovasculaire connue demeure nébuleuse dans près de la moitié des cas, même après des examens systématiques. Nous avons étudié la relation entre les événements stressants de la vie et le risque d'ACS chez des patients présentant un ACS expliqué (ACSe) ou inexpliqué (ACSi). MÉTHODOLOGIE: Des sujets ayant déjà subi un ACS ont été recrutés de manière prospective et répartis en deux sous-groupes (ACSe et ACSi), selon qu'un diagnostic a pu ou non être posé après l'ACS. On a demandé aux participants de répondre au questionnaire RLCQ (Recent Life Changes Questionnaire, questionnaire sur les changements de vie récents, version de 1997), au questionnaire SSS (Student Stress Scale, échelle d'évaluation du stress vécu par les étudiants) ou au questionnaire SRRS (Social Readjustment Rating Scale, échelle d'évaluation du réajustement social) pour les non-adultes en repensant aux événements survenus dans l'année précédant l'ACS, selon leur âge au moment de l'ACS; tous ces questionnaires mesurent le stress en unités de changement de vie (UCV). Les scores des patients ayant subi un ACS ont été comparés à ceux de sujets témoins appariés selon l'âge et le sexe. RÉSULTATS: Nous avons comparé 36 sujets ayant subi un ACS (22 ACSi et 14 ACSe; âge : 47 ± 15 ans; âge au moment de l'ACS : 40 ± 14 ans; proportion d'hommes : 50 %) à 36 sujets témoins (âge : 47 ± 15 ans; proportion d'hommes : 50 %). Il n'y avait pas de différence significative quant au score UCV entre le groupe témoin et le groupe ACS (248 ± 181 UCV vs 252 ± 227 UCV; p > 0,05). Les sujets du sous-groupe ACSe avaient un score UCV moyen significativement plus faible que ceux du sous-groupe ACSi (163 ± 183 UCV vs 308 ± 237 UCV; p = 0,030). CONCLUSIONS: Les événements stressants, plus particulièrement ceux qui entraînent un stress chronique, peuvent prédisposer des personnes autrement en bonne santé aux arythmies mortelles. Une étude plus poussée du rôle du stress dans la survenue précipitée d'un ACS s'impose.

Prospective Assessment of an Automated Intraprocedural 12-Lead ECG-Based System for Localization of Early Left Ventricular Activation.

BACKGROUND: To facilitate ablation of ventricular tachycardia (VT), an automated localization system to identify the site of origin of left ventricular activation in real time using the 12-lead ECG was developed. The objective of this study was to prospectively assess its accuracy. METHODS: The automated site of origin localization system consists of 3 steps: (1) localization of ventricular segment based on population templates, (2) population-based localization within a segment, and (3) patient-specific site localization. Localization error was assessed by the distance between the known reference site and the estimated site. RESULTS: In 19 patients undergoing 21 catheter ablation procedures of scar-related VT, site of origin localization accuracy was estimated using 552 left ventricular endocardial pacing sites pooled together and 25 VT-exit sites identified by contact mapping. For the 25 VT-exit sites, localization error of the population-based localization steps was within 10 mm. Patient-specific site localization achieved accuracy of within 3.5 mm after including up to 11 pacing (training) sites. Using 3 remotes (67.8±17.0 mm from the reference VT-exit site), and then 5 close pacing sites, resulted in localization error of 7.2±4.1 mm for the 25 identified VT-exit sites. In 2 emulated clinical procedure with 2 induced VTs, the site of origin localization system achieved accuracy within 4 mm. CONCLUSIONS: In this prospective validation study, the automated localization system achieved estimated accuracy within 10 mm and could thus provide clinical utility.

Ankyrin-B dysfunction predisposes to arrhythmogenic cardiomyopathy and is amenable to therapy.

Arrhythmogenic cardiomyopathy (ACM) is an inherited arrhythmia syndrome characterized by severe structural and electrical cardiac phenotypes, including myocardial fibrofatty replacement and sudden cardiac death. Clinical management of ACM is largely palliative, owing to an absence of therapies that target its underlying pathophysiology, which stems partially from our limited insight into the condition. Following identification of deceased ACM probands possessing ANK2 rare variants and evidence of ankyrin-B loss of function on cardiac tissue analysis, an ANK2 mouse model was found to develop dramatic structural abnormalities reflective of human ACM, including biventricular dilation, reduced ejection fraction, cardiac fibrosis, and premature death. Desmosomal structure and function appeared preserved in diseased human and murine specimens in the presence of markedly abnormal ß-catenin expression and patterning, leading to identification of a previously unknown interaction between ankyrin-B and ß-catenin. A pharmacological activator of the WNT/ß-catenin pathway, SB-216763, successfully prevented and partially reversed the murine ACM phenotypes. Our findings introduce what we believe to be a new pathway for ACM, a role of ankyrin-B in cardiac structure and signaling, a molecular link between ankyrin-B and ß-catenin, and evidence for targeted activation of the WNT/ß-catenin pathway as a potential treatment for this disease.

Mortality and Heart Failure After Upgrade to Cardiac Resynchronization Therapy.

BACKGROUND: Cardiac resynchronization therapy (CRT) is effective in treating advanced heart failure (HF), but data describing benefits and long-term outcomes for upgrades from a preexisting device are limited. This study sought to compare long-term outcomes in de novo CRT implants with those eligible for CRT with a prior device. METHODS: This is a retrospective cohort study using data from a provincial registry (2002-2015). Patients were included if they had mild-moderate HF, left ventricular ejection fraction ≤ 35%, and QRS duration ≥ 130 ms. Patients were classified as de novo CRT or upgraded to CRT from a prior device. Outcomes were mortality and composite mortality and HF hospitalization. RESULTS: There were 342 patients included in the study. In a multivariate model, patients in the upgraded cohort (n = 233) had a higher 5-year mortality rate (adjusted hazard ratio, 2.86; 95% confidence interval, 1.59-5.15; P = 0.0005) compared with the de novo cohort (n = 109) and higher composite mortality and HF hospitalization (adjusted hazard ratio, 2.60; 95% confidence interval, 1.54-4.37; P = 0.0003). CONCLUSIONS: Implantation of de novo CRTs was associated with lower mortality and HF hospitalization compared with upgraded CRTs from preexisting devices. It is unknown whether these differences are due to the timing of CRT implementation or other clinical factors. Further work in this area may be helpful to determine how to improve outcomes for these patients.

CONTEXTE: La thérapie de resynchronisation cardiaque (TRC) est efficace pour traiter l'insuffisance cardiaque avancée, mais les données décrivant les bienfaits et les résultats à long terme de la mise à niveau d'un implant déjà en place sont limitées. La présente étude visait à comparer les résultats à long terme chez les patients recevant un implant de TRC de novo et chez ceux ayant déjà un implant qui sont admissibles à une TRC. MÉTHODOLOGIE: Il s'agit d'une étude de cohorte rétrospective reposant sur les données issues d'un registre provincial (2002-2015). Les patients ont été inclus dans l'étude s'ils présentaient une insuffisance cardiaque légère ou modérée, une fraction d'éjection ventriculaire gauche ≤ 35 % et un intervalle QRS ≥ 130 ms. Les patients ont été classés dans le groupe TRC de novo ou dans le groupe TRC remplaçant un implant antérieur. Les paramètres d'évaluation étaient la mortalité et le critère regroupant la mortalité et l'hospitalisation pour insuffisance cardiaque. RÉSULTATS: En tout, 342 patients ont été inclus dans l'étude. Après analyse selon un modèle multivarié, le taux de mortalité à 5 ans était plus élevé (rapport des risques instantanés [RRI] corrigé de 2,86; intervalle de confiance [IC] à 95 % de 1,59 à 5,15], p = 0,0005) dans la cohorte TRC remplaçant un implant antérieur (n = 233) que dans la cohorte TRC de novo (n = 109), tout comme le taux pour le critère regroupant la mortalité et l'hospitalisation pour insuffisance cardiaque (RRI corrigé de 2,60; IC à 95 % de 1,54 à 4,37], p = 0,0003). CONCLUSIONS: L'implantation d'une TRC de novo était associée à un taux de mortalité et d'hospitalisation pour insuffisance cardiaque inférieur comparativement à l'implantation d'une TRC chez des patients ayant déjà un implant. On ne sait pas si ces différences sont attribuables au moment choisi pour l'implantation de la TRC ou à d'autres facteurs cliniques. D'autres études sur cette question pourraient être utiles afin de déterminer comment améliorer les résultats chez ces patients.

The Effect of Shock Burden on Heart Failure and Mortality.

BACKGROUND: Prior studies have demonstrated an association between appropriate implantable cardioverter defibrillator (ICD) shocks and mortality in clinical trials. The effect of shock burden on heart failure and mortality has not been previously studied in a large population-based cohort. METHODS: The cohort was derived using a comprehensive prospective ICD registry in the province of Nova Scotia with a mean follow-up of 4 ± 2.3 years. With the use of time-varying analysis, the relationship among shock burden, mortality, and heart failure hospitalization was determined. RESULTS: A total of 776 patients (mean age of 64.8 years) were included in the study, of whom 37% received appropriate therapy during follow-up. A single ICD shock did not confer an increased mortality risk compared with no therapy (hazard ratio [HR], 1.23; 95% confidence interval [CI], 0.84-1.79; P = 0.3), but mortality risk was significantly increased with ≥ 2 shocks (HR, 3.23; 95% CI, 2.04-5.09; P < 0.0001). There was a significant increase in heart failure hospitalization associated with receiving 1 ICD shock (HR, 2.05; 95% CI, 1.46-2.89; P < 0.0001) or more than 1 ICD shock (HR, 4.36; CI, 2.53-7.52; P < 0.0001) compared with patients receiving no ICD therapy. Patients who received antitachycardia pacing alone showed no difference in heart failure hospitalization (HR, 0.93; CI, 0.67-1.29; P = 0.7) and improved survival (HR, 0.69; CI, 0.5-0.96; P = 0.03) compared with those receiving no ICD therapy. CONCLUSION: Ventricular arrhythmia treated with appropriate ICD shocks is associated with an increased risk of heart failure hospitalization, whereas recurrent episodes of ventricular arrhythmia requiring shocks are associated with both higher mortality and higher heart failure hospitalization rates.

CONTEXTE: Des études menées antérieurement ont révélé l'existence d'un lien entre l'administration appropriée de décharges électriques au moyen d'un défibrillateur cardioverteur implantable (DCI) et la mortalité au cours des essais cliniques. L'effet de telles décharges sur l'insuffisance cardiaque et la mortalité n'avait encore jamais été étudié au sein d'une cohorte d'envergure représentative de la population. MÉTHODOLOGIE: La cohorte a été établie au moyen d'un registre prospectif exhaustif des DCI implantés chez des patients de la Nouvelle-Écosse ayant fait l'objet d'un suivi moyen de 4 ± 2,3 ans. La relation entre le fardeau imposé par les décharges, la mortalité et l'hospitalisation pour insuffisance cardiaque a été déterminée au moyen d'une analyse en fonction du temps. RÉSULTATS: Au total, 776 patients (âge moyen : 64,8 ans) ont été admis dans l'étude; 37 % d'entre eux avaient reçu un traitement approprié au cours de la période de suivi. Une seule décharge délivrée par un DCI n'augmentait pas le risque de mortalité par rapport à l'absence de traitement (rapport des risques instantanés [RRI] de 1,23; intervalle de confiance [IC] à 95 %, de 0,84 à 1,79; p = 0,3), mais le risque de mortalité était significativement accru chez les patients ayant reçu ≥ 2 décharges (RRI de 3,23; IC à 95 %, de 2,04 à 5,09; p < 0,0001). Le risque d'hospitalisation pour insuffisance cardiaque s'est révélé significativement supérieur chez les sujets ayant reçu 1 décharge par DCI (RRI de 2,05; IC à 95 %, de 1,46 à 2,89; p < 0,0001) ou plus de 1 décharge par DCI (RRI de 4,36; IC à 95 %, de 2,53-7,52; p < 0,0001), comparativement à ceux n'ayant reçu aucun traitement par DCI. On n'a observé aucune différence quant à l'hospitalisation pour insuffisance cardiaque (RRI de 0,93; IC à 95 %, de 0,67 à 1,29; p = 0,7) et à l'amélioration de la survie (RRI de 0,69; IC à 95 %, de 0,5 à 0,96; p = 0,03) chez les patients qui ont reçu uniquement une stimulation antitachycardie comparativement à ceux qui n'ont reçu aucun traitement par DCI. CONCLUSION: L'arythmie ventriculaire traitée de façon appropriée au moyen de décharges électriques délivrées par un DCI est associée à un risque accru d'hospitalisation pour insuffisance cardiaque, tandis que des épisodes récurrents d'arythmie ventriculaire exigeant un traitement par décharge électrique sont associés à des taux supérieurs de mortalité et d'hospitalisation pour insuffisance cardiaque.

Role of contact force in ischemic scar-related ventricular tachycardia ablation; optimal force required and impact of left ventricular access route.

BACKGROUND: Contact force-sensing technology has become a widely used addition to catheter ablation procedures. Neither the optimal contact force required to achieve adequate lesion formation in the ventricle, nor the impact of left ventricular access route on contact force has been fully clarified. PATIENTS AND METHODS: Consecutive patients (n = 24) with ischemic cardiomyopathy who underwent ablation for scar-related ventricular tachycardia were included in the study. All ablations (n = 25) were performed using irrigated contact force-sensing catheters (Smart Touch, Biosense Webster). Effective lesion formation was defined as electrical unexcitability post ablation at sites which were electrically excitable prior to ablation (unipolar pacing at 10 mA, 2 ms pulse width). We explored the contact force which achieved effective lesion formation and the impact of left ventricular access route (retrograde aortic or transseptal) on the contact force achieved in various segments of the left ventricle. Scar zone was defined as bipolar signal amplitude < 0.5 mV. RESULTS: Among 427 ablation points, effective lesion formation was achieved at 201 points (47.1%). Contact force did not predict effective lesion formation in the overall group. However, within the scar zone, mean contact force ≥ 10 g was significantly associated with effective lesion formation [OR 3.21 (1.43, 7.19) P = 0.005]. In the 12-segment model of the left ventricle, the retrograde approach was associated with higher median contact force in the apical anterior segment (31 vs 19 g; P = 0.045) while transseptal approach had higher median force in the basal inferior segment (25 vs 15 g; P = 0.021). In the 4-segment model, the retrograde approach had higher force in the anterior wall (28 vs 16 g; P = 0.004) while the transseptal approach had higher force in the lateral wall (21 vs 18 g; P = 0.032). There was a trend towards higher force in the inferior wall with the transseptal approach, but this was not statistically significant (20 vs 15 g; P = 0.063). CONCLUSIONS: In patients with ischemic cardiomyopathy, a mean contact force of 10 g or more within the scar zone had the best correlation with electrical unexcitability post ablation in our study. The retrograde aortic approach was associated with better contact force over the anterior wall while use of a transseptal approach had better contact force over the lateral wall.

Cost Effectiveness of Ventricular Tachycardia Ablation Versus Escalation of Antiarrhythmic Drug Therapy: The VANISH Trial.

OBJECTIVES: This analysis uses the data from the randomized controlled trial to assess the cost effectiveness of catheter ablation (n = 132) versus escalated antiarrhythmic therapy (n = 127). BACKGROUND: For survivors of myocardial infarction with implantable cardioverter-defibrillator shocks despite antiarrhythmic drugs, the VANISH (Ventricular Tachycardia Ablation Versus Escalated Antiarrhythmic Drug Therapy in Ischemic Heart Disease) trial demonstrated improved clinical outcomes with catheter ablation compared with more aggressive antiarrhythmic pharmacotherapy. METHODS: Health care resource use and quality-of-life data were used to determine the cost effectiveness of catheter ablation. Published references were used to estimate costs (in 2015 Canadian dollars). The analysis was over 3 years, with a 5% discount rate. Adjustment was made for censoring and baseline utilities. RESULTS: Ablation resulted in greater quality-adjusted life-years (QALYs) than escalated drug therapy did (1.63 vs. 1.49; difference: 0.14; 95% confidence interval [CI]: -0.20 to 0.46) and higher cost ($65,126 vs. $60,269; difference: $4,857; 95% CI: -$19,757 to $27,106); with an incremental cost per QALY gained for ablation versus escalated drug therapy of $34,057 primarily due to the initial costs of ablation, which were partially offset by the costs of subsequent ablations and adverse outcomes in the escalated drug therapy arm. For patients with amiodarone-refractory ventricular tachycardia, ablation dominated escalated drug therapy, with greater QALYs (1.48 vs. 1.26; difference: 0.22; 95% CI: -0.19 to 0.59) and lower costs ($67,614 vs. $68,383; difference: -$769; 95% CI: -$35,330 to $27,092). For those with sotalol-refractory ventricular tachycardia, ablation resulted in similar QALYs (1.90 vs. 1.90; difference: -0.00; 95% CI: -0.59 to 0.62) and higher costs ($60,455 vs. $45,033; difference: $15,422; 95% CI: -$10,968 to $48,555). CONCLUSIONS: For the total trial population, results are suggestive that ablation is cost effective compared with escalation of drug therapy. This result was only manifest for the subgroup of patients whose qualifying arrhythmia occurred despite amiodarone.

Effect of coronary revascularization on long-term clinical outcomes in patients with ischemic cardiomyopathy and recurrent ventricular arrhythmia.

BACKGROUND: Patients with ventricular tachycardia (VT) postmyocardial infarction (MI) are a higher risk group with significant morbidity and mortality. We examined the impact of prior coronary revascularization on clinical outcomes in patients with ischemic cardiomyopathy and VT. METHODS: The VANISH trial randomized 259 patients with prior MI and antiarrhythmic drug-refractory VT to receive escalated medical therapy or catheter ablation. Clinical outcomes were compared according to whether patients have undergone prior revascularization procedures. The primary outcome was a composite of death, appropriate implantable cardiac defibrillator (ICD) shock, or VT storm. The secondary outcomes included elements of the primary outcome, hospitalization, and any ventricular arrhythmia. RESULTS: 190 patients (73%) had prior coronary revascularization. Revascularization group had more men (97% vs 83%; P  =  0.0003) and patients in that group were older (mean age 69.3 ± 7.6 vs 66.7 ± 9.2; P  =  0.04), had more renal insufficiency (22.6% vs 8.7%; P  =  0.01), and were more likely to have an implanted cardiac resynchronization device (23% vs 10%, P  =  0.03) as compared with the nonrevascularized patients. There were no significant differences in baseline medication use. There was a trend toward fewer hospitalizations in the revascularization group (64% vs 77%; P  =  0.07); there were no differences in the individual outcomes of mortality, VT storm, ICD shocks, recurrent MI, or cardiac failure. CONCLUSIONS: In this cohort of patients with an ischemic cause for VT, a history of prior coronary revascularization was not associated with a reduction in ventricular arrhythmia or mortality.

Cardiac Resynchronization Therapy Reduces Ventricular Arrhythmias in Primary but Not Secondary Prophylactic Implantable Cardioverter Defibrillator Patients: Insight From the Resynchronization in Ambulatory Heart Failure Trial.

BACKGROUND: The RAFT (Resynchronization in Ambulatory Heart Failure Trial) demonstrated that cardiac resynchronization therapy (CRT) reduced both mortality and heart failure hospitalizations in patients with functional class II or III heart failure and widened QRS. We examined the influence of CRT on ventricular arrhythmias in patients with primary versus secondary prophylaxis defibrillator indications. METHODS AND RESULTS: All ventricular arrhythmias among RAFT study participants were downloaded and adjudicated by 2 blinded reviewers with an overreader for disagreements and committee review for remaining discrepancies. Incidence of ventricular arrhythmias among patients randomized to CRT-D versus implantable cardioverter defibrillator (ICD) were compared within the groups of patients treated for primary prophylaxis and for secondary prophylaxis. Of 1798 enrolled patients, 1764 had data available for adjudication and were included. Of these, 1531 patients were implanted for primary prophylaxis, while 233 patients were implanted for secondary prophylaxis; 884 patients were randomized to ICD and 880 to CRT-D. During 5953.6 patient-years of follow-up, there were 11 278 appropriate ICD detections of ventricular arrhythmias. In the primary prophylaxis group, CRT-D significantly reduced incidence ventricular arrhythmias in comparison to ICD (hazard ratio, 0.86; 95% confidence interval, 0.74-0.99; P=0.044). This effect was not seen in the secondary prophylaxis group (hazard ratio, 1.14; 95% confidence interval, 0.82-1.58; P=0.45). CRT-D was not associated with significant differences in overall ventricular arrhythmia burden in either group. CONCLUSIONS: CRT reduced the rate of onset of new ventricular arrhythmias detected by ICDs in patients without a history of prior ventricular arrhythmias. This effect was not observed among patients who had prior ventricular arrhythmias. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00251251.

Inherited heart rhythm disease: negotiating the minefield for the practicing cardiologist.

Inherited heart rhythm disorders are uncommon conditions that have emerged as a challenge to recognize and treat for the practicing clinician. The common electrical forms are long QT and Brugada syndrome, catecholaminergic ventricular tachycardia, and early repolarization syndrome. Inherited cardiomyopathies, including hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy, and left ventricular noncompaction can also cause serious cardiac rhythm disturbances and sudden death. We review the key historic and diagnostic considerations to provide guidance for day-to-day management, and the resources accessible to health care professionals and patients including a Canadian network of expert clinics. This allows for the initiation of disease-specific treatments and enables family screening. These heterogenous conditions can be challenging to diagnose with equally difficult management decisions. However, some common measures can be applied that will assist health care providers and reduce risk for patients. Condition-specific treatment strategies that are deployed in regional clinics are discussed, including the role of the referring health care team.

Differential entrainment distinguishes atrioventricular nodal reentry tachycardia from atrioventricular reentrant tachycardia.

BACKGROUND: Entrainment from the right ventricular (RV) apex and the base has been used to distinguish atrioventricular reentrant tachycardia (AVRT) from atrioventricular nodal reentry tachycardia (AVNRT). The difference in the entrainment response from the RV apex in comparison with the RV base has not been tested. METHODS: Fifty-nine consecutive patients referred for ablation of supraventricular tachycardia (SVT) were included. Entrainment of SVT was performed from the RV apex and base, pacing at 10-40-ms faster than the tachycardia cycle length. SA interval was calculated from stimulus to earliest atrial electrogram. Ventricle to atrium (VA) interval was measured from the RV electrogram (apex and base) to the earliest atrial electrogram during tachycardia. The SA-VA interval from apex and base was measured and the difference between them was calculated. RESULTS: Thirty-six AVNRT and 23 AVRT patients were enrolled. Mean age was 44 ± 12 years; 52% were male. The [SA-VA]apex-[SA-VA]base was demonstrable in 84.7% of patients and measured -9.4 ± 6.6 in AVNRT and 10 ± 11.3 in AVRT, P < 0.001. The difference was negative for all AVNRT cases and positive for all septal accessory pathways (APs). CONCLUSION: The difference between entrainment from the apex and base is readily performed and is diagnostic for all AVNRTs and septal APs.

A technique for the rapid diagnosis of wide complex tachycardia with 1:1 AV relationship in the electrophysiology laboratory.

BACKGROUND: The differential diagnosis of wide complex tachycardia (WCT) with 1:1 atrioventricular (AV) relationship is broad. Accurate identification of the tachycardia mechanism is essential for successful ablation. We suggest a simple pacing maneuver that can immediately clarify the tachycardia mechanism in the electrophysiology laboratory. METHODS: Eight consecutive patients (four males, 32 +/- 14 years) demonstrating stable sustained WCT with persistent 1:1 AV relationship during electrophysiologic testing were included in this study. During the tachycardia, atrial overdrive pacing was performed. The following responses were observed: (1) a change of the QRS morphology during atrial pacing and (2) the first return electrogram of the tachycardia, whether occurring in the atrium (AVA response) or in the ventricle (AVVA response). RESULTS: Atrial overdrive pacing was successfully performed in all patients. It was associated with either a change or narrowing of the QRS in all ventricular tachycardia (VT) patients but not in supraventricular tachycardia (SVT) patients. All VT patients had an AVVA response upon cessation of atrial overdrive pacing as opposed to AVA response in SVT patients, P = 0.029. CONCLUSION: The response to atrial overdrive pacing during WCT with 1:1 AV relationship can rapidly diagnose or rule out VT as a mechanism of tachycardia.

Canadian Cardiovascular Society Consensus Conference guidelines on heart failure--2008 update: best practices for the transition of care of heart failure patients, and the recognition, investigation and treatment of cardiomyopathies.

Heart failure is a clinical syndrome that normally requires health care to be provided by both specialists and nonspecialists. This is advantageous because patients benefit from complementary skill sets and experience, but can present challenges in the development of a common, shared treatment plan. The Canadian Cardiovascular Society published a comprehensive set of recommendations on the diagnosis and management of heart failure in January 2006, and on the prevention, management during intercurrent illness or acute decompensation, and use of biomarkers in January 2007. The present update builds on those core recommendations. Based on feedback obtained through a national program of heart failure workshops during 2006 and 2007, several topics were identified as priorities because of the challenges they pose to health care professionals. New evidence-based recommendations were developed using the structured approach for the review and assessment of evidence that was adopted and previously described by the Society. Specific recommendations and practical tips were written for best practices during the transition of care of heart failure patients, and the recognition, investigation and treatment of some specific cardiomyopathies. Specific clinical questions that are addressed include: What information should a referring physician provide for a specialist consultation? What instructions should a consultant provide to the referring physician? What processes should be in place to ensure that the expectations and needs of each physician are met? When a cardiomyopathy is suspected, how can it be recognized, how should it be investigated and diagnosed, how should it be treated, when should the patient be referred, and what special tests are available to assist in the diagnosis and treatment? The goals of the present update are to translate best evidence into practice, apply clinical wisdom where evidence for specific strategies is weaker, and aid physicians and other health care providers to optimally treat heart failure patients, resulting in a measurable impact on patient health and clinical outcomes in Canada.

The impact of warfarin use on clinical outcomes in atrial fibrillation: a population-based study.

BACKGROUND: Atrial fibrillation (AF) is the most common adult arrhythmia, and significantly increases the risk of ischemic stroke. Oral anticoagulation may be underused and may be less effective in community settings than clinical trial settings. OBJECTIVES: To determine the rates of thromboembolism and bleeding in an ambulatory cohort of patients with AF. METHODS: Observational study of Nova Scotian residents with AF identified by electrocardiogram in ambulatory settings between November 1999 and January 2001. Main outcome measures were rates of thromboembolism and bleeding over two years. RESULTS: Four hundred twenty-five patients were included in the study. The mean (+/-SD) age was 70.6+/-11.1 years, and 40% were women. Warfarin therapy was used by 68% of patients. Sixty-two per cent of patients had hypertension, 21% had a previous stroke or transient ischemic attack, 44% had congestive heart failure and 20% were diabetic. The overall rate of thromboembolic events was 2.7% in warfarin users and 8.5% in nonwarfarin users over two years, with an RR reduction of 68% (OR 0.31, 95% CI 0.09 to 0.91; P=0.047). The annual rate of ischemic stroke was 1.2% and 3.1% in warfarin and nonwarfarin users, respectively, with an RR reduction of 62% (OR 0.29, 95% CI 0.08 to 1.04; P=0.057). The overall rate of major bleeding was 2.6% in warfarin users and 1.4% in nonwarfarin users (P=0.667). The annual mortality rate was 7.79% in warfarin users and 9.93% in nonwarfarin users (P=0.192). CONCLUSIONS: Warfarin use was found to significantly reduce the rate of thromboembolic events without a concomitant increase in hemorrhagic events. The present study confirms the effectiveness of warfarin therapy in a population-based cohort.

Body-surface potential mapping to aid ablation of scar-related ventricular tachycardia.

We investigated whether body-surface potential mapping (BSPM) during catheter ablation of scar-related ventricular tachycardia (VT) could assist with the identification of VT exit sites. The study population consisted of 9 patients who underwent catheter ablation for VT, among whom 12 induced VTs with known exit sites were identified by entrainment criteria, pace mapping, or site of successful ablation. Paced activation was initiated at various intracardiac sites (20 +/- 4 sites per patient, a total of 180) documented by nonfluoroscopic electroanatomic mapping. During all episodes of VT and pacing, patients had a 120-lead electrocardiogram recorded, and we analyzed these electrocardiographic data--by means of a similarity coefficient (SC) calculated over 100 milliseconds after the initiation of depolarization--to assess the similarity between the BSPM sequences occurring during VTs and those induced by pacing. Based on 245 observations, the relationship between the SC and the distance of the pacing site from the VT exit site was then obtained for each individual VT by linear regression analysis: the distance D (in millimeters) from the VT exit site was related to SC by the regression equation D = slope (1 - SC2) + intercept. The parameters in this equation varied widely for the 12 VTs, but, in general, the nearer the pacing site was to the exit site, the better the goodness of match. This suggests that, although there is no universally applicable relationship between D and SC, BSPM could provide a useful adjunct to standard pace mapping, although additional processing--namely, an inverse calculation of epicardial potentials/isochrones--may be needed to reliably identify VT exit sites from body-surface electrocardiograms.

Population-based evaluation of the management of antithrombotic therapy for atrial fibrillation.

BACKGROUND: Oral anticoagulation is an effective therapy for the prevention of cardioembolic complications in patients with atrial fibrillation. However, previous practice reviews have indicated that oral anticoagulants are often underused in this setting. Most of those reports have focused on reviews of hospitalized and institutionalized patients, or small geographical areas. OBJECTIVES: To determine the use of antithrombotic therapy for the treatment of atrial fibrillation in Nova Scotia and to survey the knowledge of antithrombotic therapy for atrial fibrillation among a concurrent cohort of primary care and specialist physicians involved in the management of patients with atrial fibrillation. PATIENTS AND METHODS: Patients with atrial fibrillation were identified through outpatient electrocardiography clinics held throughout Nova Scotia. Following consent of the primary care physicians, patients were contacted and completed a survey about their current management. Family physicians and specialists in Nova Scotia were also surveyed about the management of atrial fibrillation with antithrombotic therapy through the receipt of one of four case scenarios. RESULTS: Four hundred twenty-five patients participated in the cross-sectional survey. The mean patient age was 70.6 years, 255 (60%) were male and 398 (93.6%) had at least one risk factor for stroke in addition to atrial fibrillation. Two hundred ninety-four patients (69.2%) were receiving oral anticoagulants either alone (61.9%) or in combination with acetylsalicylic acid (ASA) (7.3%). An additional 85 patients (20%) received ASA alone. There was no difference in the rates of prescription of oral anticoagulants between elderly patients (75 years of age and older) and those younger than 75 years (71.7% versus 67.3%, 95% CI -13.1% to 4.5%; P=0.34). Overall, 72.0% of patients were receiving antithrombotic therapy in accordance with the 2001 guidelines of the American College of Chest Physicians, with no difference in the rates between individuals younger than 75 years (72.2%) and those over 75 years of age (71.7%) (absolute difference -0.5%, 95% CI -9.2% to 8.1%). Physician responses to case scenarios indicated that knowledge was high among both general practitioners and specialists regarding the appropriate use of oral anticoagulants for the prevention of thrombotic complications associated with atrial fibrillation. CONCLUSIONS: The appropriate use of oral antithrombotic therapy for the prevention of thrombotic complications of atrial fibrillation occurs in approximately 72% of patients studied in Nova Scotia, and physician knowledge about this indication is high. There was no bias against prescribing oral anticoagulants to elderly patients. The findings suggest that with time, education and evidence have positively impacted the use of antithrombotic therapy in these patients.

Quantitative assessment of myocardial ischemia by electrocardiographic and scintigraphic imaging.

We calculated distributions of epicardial potentials from body-surface electrocardiograms (ECGs) recorded during controlled myocardial ischemia and compared them with scintigraphic estimates of ischemia's extent/severity. The study population consisted of patients suffering from single-vessel coronary artery disease, referred for elective percutaneous transluminal coronary angioplasty of either the left anterior descending (n=7), the right coronary (n=9), or the left circumflex (n=2) artery. After the target vessel had been dilated, a 1960s "study" inflation was performed with a non-perfusion-type balloon catheter; at its commencement, technetium-99m sestamibi was injected via a femoral-vein catheter, and ECGs were recorded throughout the inflation from 120 leads. Single photon emission computed tomographic imaging was performed one hour after the injection of radionuclide to obtain an "occlusion image", and again one hour after a repeat injection 24 hours later to obtain a "control image"; the latter image was subtracted from the former, to derive a scintigraphic difference map (Delta map). The ECGs were signal-averaged over a 10-s window at preinflation and peak-inflation states, the preinflation averaged complexes were subtracted from the peak-inflation ones to produce body-surface Delta maps, and the corresponding Delta maps of epicardial potentials were calculated by applying the electrocardiographic inverse solution; this procedure is referred to as electrocardiographic imaging. The ECG-derived epicardial Delta maps related spatially to the scintigraphic Delta maps in all patients. The percent areas and surface integrals of positive values in ECG-derived Delta maps were found to be very good single-variable predictors of the extent (r=0.73; p=0.0006) and severity (r=0.72; p=0.0008) of the scintigraphically-estimated perfusion defect; a regression equation using two ECG-derived predictors further improved the agreement with scintigraphic estimates (r=0.81; p=0.0004 for estimates of severity). These findings suggest that noninvasive electrocardiographic imaging might provide quantitative estimates of the extent/severity of myocardial ischemia that agree closely with those provided by scintigraphic techniques.

Is blood glucose an independent predictor of mortality in acute myocardial infarction in the thrombolytic era?

OBJECTIVES: This study was designed to assess the prognostic significance of hyperglycemia in acute myocardial infarction (AMI) in the thrombolytic era using contemporary criteria for hyperglycemia. BACKGROUND: Most studies that have examined this issue were performed before the widespread use of disease-modifying therapies and varied in their definition of hyperglycemia, assessment of risk factors, and reported outcomes. METHODS: There were 1,664 consecutively hospitalized patients with AMI between October 1997 and October 1998 from a disease-specific, population-based registry. Patients were stratified according to history of diabetes mellitus and, further, according to whether they had a blood glucose >198 mg/dl (11 mmol/l). The influences of cardiac risk factors, medications, and interventions were analyzed, and multivariate logistic regression was used to determine the influence of blood glucose on mortality. RESULTS: In patients without a history of diabetes, glucose levels were < or =198 mg/dl in 1,078 patients (Group 1) and >198 mg/dl in 135 (Group 2). Of those with diabetes, glucose levels were < or =198 mg/dl in 169 patients (Group 3) and >198 mg/dl in 282 (Group 4). Compared with Group 1 patients, the odds ratios (95% confidence interval) for in-hospital mortality among those in Groups 2, 3, and 4 were 2.44 (1.42 to 4.20; p = 0.001), 1.87 (1.05 to 3.34; p = 0.035), and 1.91 (1.16 to 3.14; p = 0.011), respectively. These groups also had greater 12-month mortality. CONCLUSIONS: Hyperglycemia in AMI is associated with poor outcome even among patients without known diabetes. This finding underlines the need for aggressive glucose management in this setting and may support a more vigorous screening strategy for early recognition of diabetes.

QT dispersion in 120 electrocardiographic leads in patients with structural heart disease.

The clinical significance of QT dispersion (QTd) measured in 12-lead ECGs is controversial. The aim of this study was to clarify factors that determine the QTd and its measurement errors in different lead arrays in patients with structural heart disease. Two blinded observers measured QT intervals on a computer screen from 120-channel ECG recordings in a retrospective set of 257 patients, comprising a group of 121 myocardial infarction (MI) survivors without ventricular tachyarrhythmia during a 6-month follow-up and a group of 136 survivors of ventricular tachyarrhythmia/fibrillation. QTd did not differ in patients with and without ventricular tachyarrhythmia/fibrillation. Eleven ventricular tachyarrhythmia/fibrillation survivors without structural heart disease had the lowest QTd (P < or = 0.02). The strongest factor determining QTd and the magnitude of its measurement error was the lead array (P = 0.0001). Measurement errors had two components. The smallest relative errors were in the total body surface mapping array with one component related to interobserver reproducibility (9.1 +/- 7.6%), and the other component related to accuracy of measurement of the QT interval (36 +/- 16%). The authors estimated that a difference of QTd of at least 50 ms between study groups is required in a 12-lead ECG to draw any conclusions from the studies. In patients with structural heart disease, QTd from limited arrays of ECG leads was not a reliable measure. It correlated with the presence of structural heart disease, but not with arrhythmogenicity. An array consisting of ECG leads covering the entire chest allowed better reproducibility and measurement accuracy of QTd.