ACC/AHA/NASPE 2002 guideline update for implantation of cardiac pacemakers and antiarrhythmia devices: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/NASPE Committee to Update the 1998 Pacemaker Guidelines)

Long QT syndrome due to a novel mutation in SCN5A: treatment with ICD placement at 1 month and left cardiac sympathetic denervation at 3 months of age

We describe the case of a newborn with congenital long QT syndrome, with 2:1 AV block and frequent episodes of Torsades de Pointes (TdP) requiring placement of a dual chamber ICD at 33 days and 3.63 kg, the youngest and smallest patient, thus far reported. Long QT syndrome was diagnosed due to bradycardia in the newborn nursery, with frequent episodes of TdP. The patient was initially treated with magnesium and esmolol then given lidocaine which resulted in dramatic transient normalization of the QTc with 1:1 AV nodal conduction. An attempt to transition to oral sodium channel and beta blockade was unsuccessful. An ICD was placed and dual chamber pacing was initiated which facilitated the transition to an oral medical regimen and ultimate discharge from the hospital. Soon after placement of the ICD, genetic testing revealed a novel F1473C mutation in the SCN5A gene. Episodes of TdP continued and left stellate gangliectomy was performed at 3 months of age. At 30 months follow-up, the patient has occasional, self-limited episodes of TdP and has received rare, successful, and appropriate ICD shocks.

Use of implantable cardioverter defibrillators for primary prevention in the community: do women and men equally meet trial enrollment criteria?

BACKGROUND

Fewer women than men undergo implantable cardioverter defibrillator (ICD) implantation for the primary prevention of sudden cardiac death. The criteria used to select patients for ICD implantation may be more permissive among men than for women. We hypothesized that women who undergo primary prevention ICD implantation more often meet strict trial enrollment criteria for this therapy.

METHODS

We studied 59,812 patients in the National Cardiovascular Data Registry ICD registry undergoing initial primary prevention ICD placement between January 2005 and April 2007. Patients were classified as meeting or not meeting enrollment criteria of either the MADIT-II or SCD-HeFT trials. Multivariable analyses assessed the association between gender and concordance with trial criteria adjusting for demographic, clinical, and system characteristics.

RESULTS

Among the cohort, 27% (n = 16,072) were women. Overall, 85.2% of women and 84.5% of men met enrollment criteria of either trial (P = .05). In multivariable analyses, women were equally likely to meet trial criteria (OR 1.04, 95% CI 0.99-1.10) than men. Significantly more women than men met the trial enrollment criteria among patients older than age 65 (86.6% of women vs 85.3% of men, OR 1.11, 95% CI 1.03-1.19), but this difference was not found among younger patients (82.5% of women vs 83.0% of men, OR 0.97, 95% CI 0.89-1.07).

CONCLUSIONS

In a national cohort undergoing primary prevention ICD implantation, older women were only slightly more likely then men to meet the enrollment criteria for MADIT II or SCD-HeFT. Relative overutilization in men is not an important explanation for gender differences in ICD implantation.

Pacing for hypertrophic obstructive cardiomyopathy does it work?

Sixty-nine years old lady presented with sudden cardiac arrest, she was found to have hypertrophic obstructive cardiomyopathy, she refused septal myomectomy and had a dual chamber ICD implanted, she was put on right ventricular apical pacing with short AV interval, after pacing her max pressure gradient across left ventricular out flow tract (LVOT) dropped from 117 mmHg to 21 mmHg and her symptoms much improved over a follow up period of 1 year.

Quantification of left ventricular asynchrony throughout the whole cardiac cycle with a computed algorithm: application for optimizing resynchronization therapy

INTRODUCTION

Measurement of left ventricular (LV) asynchrony is usually determined on single time points from spectral tissue Doppler imaging (TDI) scans that are frequently difficult to identify or not representative of the whole cardiac cycle. Our aim was to validate a new asynchrony index that evaluates the motion of the LV walls throughout the whole cardiac cycle.

METHODS AND RESULTS

Ten healthy volunteers and 50 patients undergoing cardiac resynchronization therapy (CRT) were studied with TDI. Wall displacement tracings from the septal and lateral LV walls were analyzed. Cross-correlation was calculated and 2 indices were obtained to assess LV asynchrony: the time delay and the superposition index (SI) between wall displacements. These results were compared between healthy volunteers and CRT patients, and between responders and nonresponders to CRT. Also, the optimal interventricular (VV) interval was based upon the best matching level. Volunteers showed lower asynchrony indices (83 +/- 2% SI, 17 +/- 8 ms time delay) as compared with CRT patients (63 +/- 15% SI, 73 +/- 60 ms time delay, P < 0.05). Responders also had more LV dyssynchrony than nonresponders (58 +/- 15% SI and 92 +/- 66 ms vs 68 +/- 12% and 48 +/- 34 ms, P < 0.05). The optimum VV interval selected by the computed algorithm showed an excellent concordance (Kappa = 0.90, P < 0.05) with that determined by other validated methods for optimizing the programming of CRT devices.

CONCLUSIONS

This approach allows measurement of LV intraventricular asynchrony throughout the cardiac cycle, being useful to determine the optimum VV interval and to select candidates for CRT.

Progression of conduction system disease in a paced patient with Kearns-Sayre syndrome

The Kearns-Sayre syndrome is a rare condition characterized by external ophthalmoplegia, retinal pigmentary degeneration and progressive impairment of cardiac conduction. We report a patient with the permanent pacemaker. The spontaneous cardiac impulse formation disappeared during long-term follow-up in this patient with Kearns-Sayre Syndrome.

Rapid development of life-threatening complete atrioventricular block in Kearns-Sayre syndrome

Kearns-Sayre syndrome is a rare mitochondrial disorder with defined diagnostic criteria. Knowledge of these diagnostic criteria and early diagnosis are important to ensure periodic electrocardiograms for identification of cardiac conduction disorders, which are the most important prognostic factor of the disease. We report on a 9-year-old girl with rapid development of a life-threatening complete atrioventricular block within 10 months and discuss the importance and time interval of regular electrocardiograms. Our patient survived by placing a temporary transvenous pacemaker lead followed by permanent pacemaker implantation a few days later.

Genetic evaluation of cardiomyopathy--a Heart Failure Society of America practice guideline

Substantial progress has been made recently in understanding the genetic basis of cardiomyopathy. Cardiomyopathies with known genetic cause include hypertrophic (HCM), dilated (DCM), restrictive (RCM), arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) and left ventricular noncompaction (LVNC). HCM, DCM, and RCM have been recognized as distinct clinical entities for decades, whereas ARVD/C and LVNC are relative newcomers to the field. Hence the clinical and genetic knowledge for each cardiomyopathy varies, as do the recommendations and strength of evidence.

Predictors of implantable cardioverter defibrillator shocks during the first year

The purpose of this study was to predict implantable cardioverter defibrillator (ICD) shocks using demographic and clinical characteristics in the first year after implantation for secondary prevention of cardiac arrest. A prospective design was used to follow 168 first-time ICD recipients over 12 months. Demographic and clinical data were obtained from medical records at the time of ICD insertion. Implantable cardioverter defibrillator shock data were obtained from ICD interrogation reports at hospital discharge, 3, 6, and 12 months. Logistic regression was used to predict ever receiving an ICD shock using background characteristics. Patients received an ICD for secondary prevention of sudden cardiac arrest, they were 64.1 years old, 89% were white, 77% were male, with a mean (SD) ejection fraction of 33.7% (14.1%). The cumulative percentage of ever receiving an ICD shock was 33.3% over 1 year. Three variables predicted shocks in the first year: history of chronic obstructive pulmonary disease (COPD) (odds ratio [OR], 4.42; 95% confidence interval [CI], 1.2-16.4; P = .03), history of congestive heart failure (OR, 3.55; 95% CI, 1.4-9.3; P = .01), and documented ventricular tachycardia (VT) at the time of ICD implant (OR, 10.05; 95% Cl, 1.8-55.4; P = .01). High levels of anxiety approached significance (OR = 2.82; P = .09). The presence of COPD, congestive heart failure, or VT at ICD implant was a significant predictor of receiving an ICD shock in the first year after ICD implantation. Because ICD shocks are distressing, painful, and associated with greater mortality, healthcare providers should focus attention on prevention of shocks by controlling VT, careful management of HF symptoms, reduction of the use of short acting beta agonist medications in COPD, and perhaps recognizing and treating high levels of anxiety.

Usefulness of clinical and electrocardiographic data for predicting adverse cardiac events in patients with myotonic dystrophy

BACKGROUND

Myotonic dystrophy type 1 (DM1) has been associated with an increased risk of sudden death, either by heart block or malignant ventricular arrhythmias. Identifying patients at risk remains difficult and no consensus has been reached regarding the best approach for follow-up and prevention of sudden death.

OBJECTIVES

To identify noninvasive clinical and electrocardiographic predictors of adverse cardiac events in patients with DM1.

METHODS

Clinical and serial electrocardiographic data on 428 patients with a DNA-proven diagnosis of DM1, followed during a mean period of 11.7 years, were reviewed. Variables associated with adverse cardiac events were identified.

RESULTS

Eleven patients (2.6%) experienced sudden death and 13 (3.0%) required implantation of a pacemaker. On univariate analysis, adverse events were associated with advancing age, prolongation of the PR, QRS and corrected QT (QTc) intervals, as well as the degree of neuromuscular impairment. No such relationship was found with the extent of genetic anomaly (number of cytosine-thymine-guanine repeats). However, multivariate analysis using Cox proportional hazards models showed that only baseline PR and QTc intervals were significantly linked to the end points of sudden death or pacemaker implantation; the age-adjusted RR was 3.7 (95% CI 1.5 to 8.6) if baseline PR was 200 ms or longer (P=0.003), and 3.0 (95% CI 1.0 to 8.8) if the baseline QTc was 450 ms or longer (P=0.047).

CONCLUSIONS

In a large unselected cohort of 428 patients with DM1, the cumulative incidence of sudden death was relatively low, and the delayed conduction on surface electrocardiogram was found to be potentially helpful for identifying patients at risk for sudden death or pacemaker implantation.

Incidence and prognostic significance of sustained ventricular tachycardias in heart failure patients implanted with biventricular pacemakers without a back-up defibrillator: results from the prospective, multicentre, Mona Lisa cohort study

AIMS

The aim of this study was to investigate the 12-month incidence, predictive factors, and prognosis of sustained ventricular tachycardia (VT) in chronic heart failure patients implanted with biventricular pacemakers without a back-up defibrillator (CRT-P), assessed by continuous intracardiac ventricular electrograms.

METHODS AND RESULTS

The Mona Lisa study, a prospective, multicentre, cohort study, designed to determine the incidence of sustained VT and its prognostic impact in CRT-P recipients within the year after implant enrolled 198 patients with moderate or severe chronic heart failure, despite optimal pharmacological therapy. An independent committee reviewed the data from all arrhythmic episodes as well as causes of death according to predefined criteria. During a mean follow-up of 9.8 +/- 3.1 months after implantation, 8 patients experienced at least one episode of sustained VT [4.3%; 95% confidence interval (CI), 1.1-7.5] and 21 deaths occurred, giving a 12-month mortality rate of 11.7% (95% CI, 6.4-16.9). The presence of sustained VT was associated with a high risk of sudden cardiac death (SCD) and the lowest 12-month overall survival (P < 0.0001).

CONCLUSION

The incidence of sustained VT remains relatively low in the first year after CRT-P implantation, but when present appears closely associated with short-term adverse outcomes, especially SCD. This emphasizes the possible value of remote monitoring to detect high-risk patients for urgent upgrading.

Utility of QRS width and echocardiography parameters in an integrative algorithm for selecting heart failure patients with cardiac dyssynchrony

BACKGROUND

Cardiac resynchronization therapy (CRT) is an effective treatment in dilated cardiomyopathy (DCM). However, it has been demonstrated that mechanical dyssynchrony is not related to electrical dyssynchrony. We hypothesized that a new QRS width cutoff could be easier to use as a first step in the selection of patients with inter- and intraventricular dyssynchrony.

METHODS

We included 58 patients with DCM. Electrocardiographic (PR interval and QRS width) and echocardiographic (left ventricular dimensions, systolic and diastolic function, dyssynchrony parameters) data were evaluated in all patients.

RESULTS

According to QRS width, we divided the study population in two groups: Group 1, 25 patients having a narrow QRS (<or=120 ms), and Group 2, 33 patients having a wide QRS (>120 ms). Patients in Group 2 had larger left ventricles, with similar systolic function and more severe diastolic dysfunction than patients with narrow QRS. Interventricular dyssynchrony was more frequent in group 2 (54.5% vs 20%, p=0.01), while intraventricular dyssynchrony was highly prevalent in both groups (82.1% vs 72%, p=0.48). A QRS>140 ms best predicted the presence of interventricular dyssynchrony (sensitivity 78.2% and specificity 63.6%), while a QRS>150 ms best predicts intraventricular dyssynchrony (sensitivity 48.6% and specificity 80%).

CONCLUSIONS

Intraventricular dyssynchrony has a high prevalence in patients with DCM, irrespective of the QRS width. Using a higher QRS width cutoff (150 ms) might help in patient selection for CRT. Electrocardiography and echocardiography can be combined into a selection algorithm for patients receiving resynchronization therapy.

The role of the out-of-operating room anesthesiologist in the care of the cardiac patient

Modern invasive cardiovascular procedures require patients to be both comfortable and cooperative. In addition, these procedures demand the complete attention of the attending cardiovascular specialist, and, to a large degree, the outcomes of these procedures depend on the amount of focus and concentration the cardiovascular specialist can give to performing the procedure itself. A team approach using the specialized skills of a cardiologist and an anesthesiologist frequently is required to optimize results. This article clearly delineates the procedures cardiologists perform that might involve anesthesiologists. Mutual knowledge, understanding, and respect are fundamental requirements for integration of cardiology and anesthesia services to optimize patient outcomes.

A randomized study to compare ramp versus burst antitachycardia pacing therapies to treat fast ventricular tachyarrhythmias in patients with implantable cardioverter defibrillators: the PITAGORA ICD trial

BACKGROUND

In patients with implantable cardioverter-defibrillators (ICDs), antitachycardia pacing (ATP) is highly effective in terminating fast ventricular tachycardias (FVTs) and lowers the use of high-energy shocks, without increasing the risk of arrhythmia acceleration or syncope.

METHODS AND RESULTS

The aim of the PITAGORA ICD trial was to randomly compare 2 ATP strategies (88% coupling interval burst versus 91% coupling interval ramp, both 8 pulses) in terms of ATP efficacy, arrhythmia acceleration, and syncope. Two hundred six ICD patients (83% male, 67+/-11 years) were enrolled. FVT episodes with cycle lengths between 240 and 320 ms were treated by 1 ATP sequence and, in the event of failure, by shocks. Over a median follow-up of 36 months, 829 spontaneous ventricular tachyarrhythmia episodes were detected in 79 patients. Episode review identified 595 episodes as true ventricular arrhythmias in 72 patients; devices classified 111 (18.7%) episodes as VF, 216 (36.3%) as FVT, and 268 (45.0%) as VT. Fifty-six patients had 214 treated FVT episodes-2 FVTs self-terminated before ATP release; 44 (79%) of these had at least 1 effective ATP intervention, and 34 (61%) were spared ICD shocks. Burst terminated 100 of 133 (75.2%) FVT episodes, whereas ramp terminated 44 of 81 (54.3%; P=0.015). Acceleration occurred in 9 of 214 (4.2%) FVT episodes treated: 6 episodes in 3 ramp patients and 3 episodes in 3 burst patients. Two patients-1 in each group-suffered 1 syncopal event associated to a nonterminated FVT episode.

CONCLUSIONS

Burst is significantly more efficacious than ramp in terminating FVT episodes. As the first therapy for FVT episodes, ATP carries a low risk of acceleration or syncopal events.

[ICD lead defects: diagnosis and therapeutical options]

The number of cardioverter/defibrillator (ICD) implantations has been steadily increasing; thus, ICD lead-associated complications are an important issue. No clear recommendations for the diagnosis and management are available. This article gives an overview of how to diagnose and manage an ICD lead defect. Possible therapeutic options are discussed by reviewing the literature.

Procedural and 30-day outcomes following transcatheter aortic valve implantation using the third generation (18 Fr) corevalve revalving system: results from the multicentre, expanded evaluation registry 1-year following CE mark approval

AIMS

To describe the procedural performance and 30-day outcomes following implantation using the 18 Fr CoreValve Revalving System (CRS) as part of the multicentre, expanded evaluation registry, 1-year after obtaining CE mark approval.

METHODS AND RESULTS

Patients with symptomatic severe aortic stenosis and logistic Euroscore > or =15%, or age > or =75 years, or age > or =65 years associated with pre-defined risk factors, and for whom a physician proctor and a clinical specialist were in attendance during the implantation and who collected the clinical data, were included. From April 2007, to April 2008, 646 patients with a mean age of 81 +/- 6.6 years, mean aortic valve area 0.6 +/- 0.2 cm2, and logistic EuroSCORE of 23.1 +/- 13.8% were recruited. After valve implantation, the mean transaortic valve gradient decreased from 49.4 +/- 13.9 to 3 +/- 2 mmHg. All patients had paravalvular aortic regurgitation < or = grade 2. The rate of procedural success was 97%. The procedural mortality rate was 1.5%. At 30 days, the all-cause mortality rate (i.e, including procedural) was 8% and the combined rate of death, stroke and myocardial infarction was 9.3%.

CONCLUSIONS

The results of this study demonstrate the high rate of procedural success and a low 30-day mortality in a large cohort of high-risk patients undergoing transcatheter aortic valve implantation (TAVI) with the CRS.

[Implantable pacemakers and defibrillators: implications for anesthesia and perioperative management]

The technological complexity of implantable devices for managing arrhythmias, specifically pacemakers and defibrillators, has increased spectacularly since their introduction a few decades ago. A growing number of patients with these devices are undergoing surgery and it is therefore essential to understand how they work and what the real associated risks are. Manuals and reference works on anesthesia may provide little information on these devices and their perioperative management. It is no longer satisfactory to place a magnet over these devices during surgery and assume that this action will protect the patient from the possible effects of electromagnetic interference. This review examines the basic principles and operation of implantable pacemakers and defibrillators, the relevant nomenclature, and the sources and effects of electromagnetic interference; the current recommendations for the perioperative management of patients fitted with these devices are also discussed.

Avoid delivering therapies for nonsustained fast ventricular tachyarrhythmia in patients with implantable cardioverter/defibrillator: the ADVANCE III Trial

INTRODUCTION

The purpose of this investigation is to evaluate whether a prolonged detection interval for life threatening ventricular tachyarrhythmia (VT) is able to reduce therapies (Rx) delivered by an implantable cardioverter/defibrillator (ICD). Until now, only the PREPARE trial demonstrated a reduction of ICD Rx in a cohort of primary prevention patients.

METHODS AND RESULTS

The ADVANCE III study is a prospective, randomized, parallel trial with 2 arms evaluating different intervals to detect (NID), i.e., 18/24 (as currently used) versus 30/40. The primary endpoint is to demonstrate a 20% reduction of ICD Rx (antitachycardia pacing or shocks) delivered to terminate spontaneous VT with a cycle length < or =320 ms in patients with Class I-IIA indication for ICD therapy, regardless of cardiac resynchronization capabilities. The worldwide investigation started in spring 2008 and is expected to be finished in 2011.

CONCLUSIONS

The ADVANCE III trial is the first randomized investigation evaluating the reduction of ICD Rx for fast VT due to a prolongation of NID in a general ICD patient cohort.

Improved Stratification of Autonomic Regulation for risk prediction in post-infarction patients with preserved left ventricular function (ISAR-Risk)

Aims

To investigate the combination of heart rate turbulence (HRT) and deceleration capacity (DC) as risk predictors in post-infarction patients with left ventricular ejection fraction (LVEF) > 30%.

Methods and results

We enrolled 2343 consecutive survivors of acute myocardial infarction (MI) (<76 years) in sinus rhythm. HRT and DC were obtained from 24 h Holter recordings. Patients with both abnormal HRT (slope ≤ 2.5 ms/RR and onset ≥ 0%) and abnormal DC (≤4.5 ms) were considered suffering from severe autonomic failure (SAF) and prospectively classified as high risk. Primary and secondary endpoints were all-cause, cardiac, and sudden cardiac mortality within the first 5 years of follow-up. During follow-up, 181 patients died; 39 deaths occurred in 120 patients with LVEF ≤ 30%, and 142 in 2223 patients with LVEF>30% (cumulative 5-year mortality rates of 37.9% and 7.8%, respectively). Among patients with LVEF > 30%, SAF identified another high-risk group of 117 patients with 37 deaths (cumulative 5-year mortality rates of 38.6% and 6.1%, respectively). Merging both high-risk groups (i.e. LVEF ≤ 30% and/or SAF) doubled the sensitivity of mortality prediction compared with LVEF ≤ 30% alone (21.1% vs. 42.1%, P < 0.001) while preserving 5-year mortality rate (38.2%).

Conclusion

In post-MI patients with LVEF>30%, SAF identifies a high-risk group equivalent in size and mortality risk to patients with LVEF ≤ 30%.

Safety of magnetic resonance imaging of patients with a new Medtronic EnRhythm MRI SureScan pacing system: clinical study design

BACKGROUND

Magnetic Resonance Imaging (MRI) of patients with implanted cardiac devices is currently considered hazardous due to potential for electromagnetic interference to the patient and pacemaker system. With approximately 60 million MRI scans performed worldwide per year, an estimated majority of pacemaker patients may develop an indication for an MRI during the lifetime of their pacemakers, suggesting that safe use of pacemakers in the MRI environment would be clinically valuable. A new pacing system (Medtronic EnRhythm MRI(TM) SureScan(TM) and CapSureFix MRI(TM) leads) has been designed and pre-clinically tested for safe use in the MRI environment. The EnRhythm MRI study is designed to confirm the safety and efficacy of this new pacing system.

METHODS

The EnRhythm MRI study is a prospective, randomized controlled, unblinded clinical trial to confirm the safety and efficacy of MRI at 1.5 Tesla in patients implanted with a specifically designed pacemaker and lead system. The patients have standard indications for dual chamber pacemaker implantation. Successfully implanted patients are randomized in a 2:1 ratio to undergo MRI (MRI group) or to have no MRI scan (control group) at 9-12 weeks after pacemaker system implantation. Magnetic resonance (MR) scanning includes 14 head and lumbar scan sequences representing clinically relevant scans while maximizing the gradient slew rate up to 200 T/m/s, and/or the transmitted radiofrequency (RF) power up to SAR (specific absorption rate) levels of 2 W/kg body weight (upper limit of normal operating mode). Full interrogation of all device information and sensing and capture function are measured at device implantation, every follow-up and before and immediately after MRI in the MRI group and at the same time points in the control group. Complete pacemaker and lead evaluations are also done at one week and one month after the scan for the MRI and control group patients.The primary endpoint is safe and successful completion of the MRI scan as measured by freedom from both MRI-procedure related complications and clinically significant changes in the sensing and capture function of the leads.

RESULTS

Results will be communicated after approximately 156 and 470 patients have completed 4 months of follow-up.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00433654.

Therapeutic considerations in applying rate control therapy for atrial fibrillation

The therapeutic strategy of heart rate control for atrial fibrillation (AF) is undergoing a renaissance since several recent randomized trials demonstrated clear advantages over the rhythm control for many patients. Heart rate control for AF is hampered, however, by a dearth of information relating target heart rates to physiological measures or clinical outcomes. In this review, the rather sparse rationale behind the data elements for heart rate control - resting heart rate, activity heart rate, and regularity of the heart rate, is outlined. Beat-to-beat stroke volume is probably a key variable for calibrating heart rate targets. Presently it seems reasonable to propose targets for resting and activity heart rates but not for regularity. It also seems plausible but remains unproven that there should be a range (upper and lower) of heart rate targets rather than a simple upper limit. Nevertheless, it remains to be demonstrated through randomized clinical trials how to apply various heart rate control targets in patients with AF and whether complexity offers any advantage over simplicity.

Optimal site for atrial lead implantation in myotonic dystrophy patients: the role of Bachmann's Bundle stimulation

AIM

The aim of this study was to identify the optimal site for atrial lead implantation in myotonic dystrophy type 1 (MD1) patients.

METHODS

The atrial pacing lead was positioned in the high-lateral right atrial wall (site A), then in the right atrial appendage (site B), and finally on the interatrial septum (site C) in 22 patients. Pacing and sensing thresholds were obtained for all sites. The lead was repositioned and fixed at the optimal site, defined as the location with the lowest pacing and the highest sensing thresholds.

RESULTS

Mean pacing thresholds were 1.46 +/- 0.32 V at site A, 1.45 +/- 0.33 V at site B, and 0.84 +/- 0.24 V at site C. P-wave amplitude was 1.52 +/- 0.45 mV at site A, 1.52 +/- 0.49 mV at site B, and 2.60 +/- 0.48 mV at site C. Atrial lead was implanted at site C in all patients without complications.

CONCLUSIONS

Interatrial septum in the region of Bachmann's Bundle seems to be the optimal site for atrial lead implantation in MD1 patients.

Presence and duration of atrial fibrillation detected by continuous monitoring: crucial implications for the risk of thromboembolic events

INTRODUCTION

Asymptomatic atrial fibrillation (AF) can expose patients to the risk of stroke. The primary objective of this study was to assess the incidence of thromboembolic events in relationship with CHADS(2) (congestive heart failure, hypertension, age >or=75 years, diabetes mellitus, and prior stroke, or transient ischemic attack) score and AF presence/duration. The secondary objective was to compare intermittent versus continuous monitoring strategies.

METHODS AND RESULTS

Data from patients with an implanted pacemaker and a history of AF were analyzed. Thromboembolic risk was quantified through CHADS(2) score. Three AF groups were considered: patients with <5-minutes AF on 1 day (AF-free); patients with >5-minutes AF on 1 day but <24 hours (AF-5 minutes); patients with AF episodes >24 hours (AF-24 hours). Monitoring strategies involving 24-hour Holter, 1-week Holter, and 30-day Holter were simulated. Data from 568 patients continuously monitored for 1 year were analyzed: 171 (30%) had CHADS(2) score = 0; 269 (47%) had CHADS(2) score = 1; 111 (20%) had CHADS(2) score = 2; and 17 (3%) had CHADS(2) score >or= 3. During follow-up, 14 patients (2.5%) had an ischemic thromboembolic event. AF-24 hours patients numbered 223 (39.2%); AF-5 minutes, 179 (31.5%); and AF-free, 29.2%. By combining AF presence/duration with CHADS(2) score, two subpopulations with markedly different risks of events (0.8% vs 5%, P = 0.035) were identified, the former corresponding to AF-free with CHADS(2)<or=2, or AF-5 minutes with CHADS(2)<or=1, or AF-24 hours with CHADS(2)= 0. The mean sensitivity in detecting an AF episode lasting >5 minutes was 44.4%, 50.4%, and 65.1% for 24-hour Holter, 1-week Holter, and 1-month Holter monitoring, respectively.

CONCLUSION

In patients with recurrent AF episodes, risk stratification for thromboembolic events can be improved by combining CHADS(2) score with AF presence/duration.

Cost of preimplantation cardiac imaging in patients referred for a primary-prevention implantable cardioverter-defibrillator

Recent guidelines have focused on ejection fraction cut-off values to determine eligibility for primary-prevention implantable cardioverter-defibrillators (ICDs). Clinical trials that led to the guidelines used varying techniques for ejection fraction assessment, including echocardiography and multigated acquisition (MUGA) scan. A prospective cohort study to determine the economic attractiveness of repeated echocardiography and MUGA scanning during the evaluation process of patients referred for consideration of a primary-prevention ICD was undertaken. From January 2005 to December 2006, data were collected for patients aged >18 years with ejection fraction <30% referred for a primary-prevention ICD based on referral assessment of heart function in any form. Costs based on the 2006 Ontario Health Insurance Plan fee schedule were determined for clinical assessment, echocardiography, MUGA scanning, and ICD implantation in patients who remained eligible based on MUGA ejection fraction. The 100 patients (age 61.1 +/- 10.2 years; 78 men) assessed for primary-prevention ICD implantation had an ejection fraction of 28.9 +/- 12.3% using MUGA scan. Thirty-one of 100 patients (31%) had an ejection fraction >30% and were no longer eligible for an ICD. Although imaging increased preimplantation cost from dollars 130 to dollars 536 per patient, averted inappropriate ICDs decreased the overall per-patient cost from dollars 20,914 to dollars 14,877. Despite an additional testing cost of dollars 40,599, the overall cost savings was dollars 603,722 in the 100 patients, with a cost savings of dollars 6,037 per patient. In conclusion, verification of ejection fraction identified a significant proportion of patients who were not eligible for an ICD.

Pacemaker and defibrillator therapy in pediatrics and congenital heart disease

Pacemakers and defibrillators have a growing use in pediatrics and in patients with congenital heart disease, but they present unique problems and implications for their implantation and follow-up. Congenital and surgically acquired rhythm disturbances are common, but the efficacy of device therapy is not well established in these patient groups. The diversity and complexity of pediatric patients and congenital heart disease make device management a highly individualized art. There are technical issues related to device implantation that have necessitated novel approaches to using leads and device that were not designed with children specifically in mind. The current guidelines and indications for implantable device therapy for children and congenital heart disease are reviewed, as well as some of the specific limitations and problems encountered.

Gated myocardial perfusion SPECT asynchrony measurements in patients with left bundle branch block

PURPOSE

This investigation sought to determine which newly available asynchrony parameter derived from gated myocardial perfusion SPECT (GMPS) systolic wall thickening data best distinguishes patients with left bundle branch block (LBBB) from normal subjects.

METHODS AND MATERIALS

Emory Cardiac Toolbox (ECTb) algorithms were used to compute left ventricular (LV) global and regional function and perfusion indices with regional contraction phases for 20 patients with LBBB, and in 9 control (CTL) subjects who had no function or perfusion abnormalities. Histogram plots of phase frequencies versus R-R interval times included phase standard deviation (SD), bandwidth (BW), skewness and kurtosis. Z-score asynchrony measures were derived for phases sampled using the conventional 17-segment model.

RESULTS

In CTLs contraction occurred nearly simultaneously in all segments, while LBBBs exhibited a wide variety of heterogeneous contraction patterns. Global parameters that differed between LBBBs versus CTLs included EF, end-systolic volume and end-diastolic volume, and asynchrony measures that were different included BW, phase SD and z-scores. Z-scores most strongly discriminated LBBBs from CTLs (93% of cases correctly predicted, logistic regression chi(2) = 29.7, P < 0.0001). Z-scores, phase SD and lateral-septal wall timing were highly reproducible (r = 0.99, 0.99 and r = 0.87, respectively), with no significant inter-observer differences.

CONCLUSION

While traditional global function parameters were different in LBBBs and CTLs, asynchrony parameters characterized LBBB most strongly.

Cardiac incoordination induced by left bundle branch block: its relation with left ventricular systolic function in patients with and without cardiomyopathy

Background

Although left bundle branch block (LBBB) alters the electrical activation of the heart, it is unknown how it might change the process of myocardial coordination (MC) and how it may affect the left ventricular (LV) systolic function. The present study assessed the effects of LBBB on MC in patients with LBBB with and without dilated (DCMP) or ischemic cardiomyopathy (ICMP).

Methods

Tissue Doppler echocardiography (TDE) was performed in 86 individuals: 21 with isolated LBBB, 26 patients with DCMP + LBBB, 19 patients with ICMP + LBBB and in 20 healthy individuals (Controls). MC was assessed analyzing the myocardial velocity profiles obtained from six basal segments of the LV using TDE. The LV systolic function was assessed by standard two-dimensional echocardiography and by TDE.

Results

Severe alterations in MC were observed in subjects with LBBB as compared with controls (P < 0.01 for all comparisons); these derangements were even worse in patients with DCMP and ICMP (P < 0.001 for comparisons with Controls and P < 0.01 for comparison with individuals with isolated LBBB). Some parameters of MC differed significantly between DCMP and ICMP (P < 0.01). A good or very good correlation coefficient was found between variables of MC and variables of LV systolic function.

Conclusion

LBBB induces severe derangement in the process of MC that are more pronounced in patients with cardiomyopathies and that significantly correlates with the LV systolic function. The assessment of MC may help in the evaluation of the etiology of dilated cardiomyopathy.