Effect of low estrogen states in healthy women on dispersion of ventricular repolarization.

Our data show that although estrogen does not seem to affect the QT interval in healthy women, it significantly decreases the QT dispersion. This finding could provide an explanation to the gender differences in susceptibility to ventricular arrhythmias, besides the difference in the incidence of coronary artery disease.

Long-term outcome of patients with syncope associated with coronary artery disease and a nondiagnostic electrophysiologic evaluation.

Syncope in the patient with structural heart disease and a nondiagnostic noninvasive workup is a generally accepted indication for an invasive electrophysiologic study. However, if the electrophysiologic evaluation is not highly sensitive, arrhythmic causes of syncope may not be discovered. In these patients, recurrent syncope and even sudden death may be observed at follow-up. Thus, we evaluated long-term follow-up in 68 consecutive patients who presented with syncope, coronary artery disease, and who had a negative invasive electrophysiologic evaluation. At a mean follow-up of 30 +/- 18 months (range 1 to 65), there have been 2 sudden deaths and 1 episode each of ventricular fibrillation and ventricular tachycardia in patients treated with an implantable cardioverter-defibrillator. All 4 arrhythmias occurred in patients with left ventricular fractions < or = 25%. Seventeen patients had recurrent presyncope or syncope. Bradycardia causing syncope was found in 8 of these patients. A bundle branch block at the initial evaluation predicted for the occurrence of bradycardia at follow-up. We conclude that in patients with coronary artery disease and syncope, noninducibility at electrophysiologic study predicts a lower risk of sudden death and ventricular arrhythmias. However, in patients with a reduced ejection fraction, the risk of sudden death and ventricular arrhythmias remains up to 10%/year and these patients may warrant treatment with implantable cardioverter-defibrillators. Recurrent syncope is common, and frequently a bradyarrhythmia is found to be the cause. Treatment of selected patients (especially those with bundle branch blocks) with permanent pacemakers may be justified.

Analysis of intracardiac electrograms showing monomorphic ventricular tachycardia in patients with implantable cardioverter-defibrillators.

Ventricular tachycardia (VT) initiation and its relation to various clinical factors was studied by reviewing intracardiac electrograms from patients with implantable cardioverter-defibrillators. Events were divided into (1) sudden onset without preceding ventricular premature complexes (VPCs), (2) extrasystolic onset with VPCs, or (3) paced, depending on the type and morphology of the last 5 beats before initiation of VT. Prematurity index, sinus rate, cycle length, and presence of short-long-short sequence for each episode was noted. A total of 268 episodes of VT among 52 patients were analyzed. Extrasystolic initiation was the most frequent pattern (177; 66%) followed by sudden onset (75; 28%) and paced (16; 6%). Among extrasystolic onset, 99 episodes (56%) were due to multiple VPCs and 149 episodes (84%) had different VPC morphology than the subsequent VT. Among pacing-induced VT, 13 of 16 episodes were due to inappropriate pacing due to undersensing of prior R waves. Sudden-onset episodes were slower (mean cycle length 383+/-97 ms) than extrasystolic (mean cycle length 336+/-88 ms, p = 0.002) and paced (mean cycle length 313+/-85 ms, p = 0.01) onset. Patients in the sudden-onset group had better left ventricular ejection fraction (33+/-15%) than the extrasystolic (29+/-11%, p<0.001) and paced (28+/-14%, p<0.01) groups. Extrasystolic onset with multiple, late coupled VPCs was the most common pattern of VT initiation and was associated with lower ejection fraction. Sudden-onset initiation was more common with better preserved systolic function.

Comparison of frequency of complications of implantable cardioverter-defibrillators in children versus adults.

Compared with adults patients (n = 309) receiving implantable cardioverter-defibrillators at the same institution, pediatric patients (n = 11) exhibited a trend toward lower defibrillation thresholds. At follow-up of 29 +/- 17 months, the incidence of recurrent arrhythmias was similar, but lead revisions and device infections were more common in the pediatric patients.

Torsade de pointes and prolonged QT interval from surreptitious use of sotalol: use of drug levels in diagnosis.

Torsade de pointes is a well-established toxic effect of sotalol hydrochloride. In a patient presenting with torsade de pointes and a long QTc interval of unknown cause, a serum sotalol level was used to secure an otherwise difficult diagnosis.

Benign lipid envelope of the heart simulating a pericardial hematoma.

The hallmark of diagnosing a pericardial effusion by echocardiography is the presence of relatively sonolucent space outside of the cardiac structures. The location, size, mobility, and consistency of the pericardial space determined by echocardiography are considered to be reliable markers for defining pericardial processes. In certain clinical scenarios, however, it may be difficult to differentiate fluid from other pericardial processes, notably subepicardial adipose tissue. This case of a 76-year-old woman, who presented with possible cardiac tamponade after permanent pacemaker implantation, demonstrates some of the potential pitfalls in the diagnosis of pericardial space abnormalities.

Atrioventricular junctional ablation and modification for atrial fibrillation.

RF catheter ablation is a safe and extremely effective method of achieving complete A-V block in patients with difficult-to-control ventricular rates in atrial fibrillation. In selected patients, A-V junction ablation may improve exercise capacity and functional status while reducing the need for emergency care and hospitalization. Prospective, randomized studies are needed, however, to compare A-V junction ablation as a management strategy to pharmacologic therapy to control ventricular rate or to maintain sinus rhythm. Similarly, additional data are needed to assess methods of achieving A-V junction modification with the lowest risk for A-V block.

Microwave radiometric thermometry and its potential applicability to ablative therapy.

INTRODUCTION: [corrected] Current techniques for estimating catheter tip temperature in ablative therapy for cardiac arrhythmias rely on thermocouples or thermistors attached to or embedded in the tip electrode. These methods may reflect the electrode temperature rather than the tissue temperature during electrode cooling so that the highest temperature away from the ablation site may go undetected. A microwave radiometer is capable of detecting microwave radiation as a result of molecular motion. In this study, we evaluated microwave radiometric thermometry as a new technique to monitor temperature away from the electrode tip during ablative therapy utilizing a saline model. METHODS AND RESULTS: A microwave radiometer antenna and fluoroptic thermometer were inserted in a test tube with circulating room temperature saline kept constant at 23.5 degrees C while the surrounding saline bath was heated from 37 degrees C to 70 degrees C. For every degree rise in the warm saline bath placed either 5 mm or 8 mm from the radiometer antenna, the radiometer temperature changed 0.26 degrees C and 0.14 degrees C respectively while the fluoroptic temperature probe remained constant at 23.5 degrees C. The radiometer temperature was highly correlated with the warm saline bath temperature (R(2)=0.997 for warm saline 5 mm from the antenna, R(2)=0.991 for warm saline 8 mm from the antenna). CONCLUSIONS: Microwave radiometry can estimate distant temperatures by detecting microwave electromagnetic radiation. The sensitivity of the microwave radiometer is also distance-dependent. The microwave radiometer thus serves as a promising instrument for monitoring temperatures at depth away from the catheter-electrode tip in ablative therapy for cardiac arrhythmias.

Effect of saline irrigation flow rate on temperature profile during cooled radiofrequency ablation.

INTRODUCTION: Cooled radiofrequency ablation has been developed clinically for the treatment of ventricular tachycardia. Although clinical studies employ a constant saline flow rate for cooling, we hypothesized that varying the flow rates might optimize the temperature profile at depth. METHODS: In excised ovine left ventricle, we compared the temperature profile from a catheter tip electrode thermocouple to those placed at depths of 0.0 mm, 1.0 mm, and 2.0 mm. We compared the following settings: 20 Watts without flow, 20 Watts with 0.3 cc/sec flow, 20 Watts with 0.5cc/sec flow, and 70C surface temperature without flow (temperature control). RESULTS: The temperatures decreased from 77.5 +/-10.5 degrees C, 91.7+/-6.3 degrees C, 65.5 +/- 11.8 degrees C, and 52.5 +/- 11.8 degrees C at 20W without saline irrigation at the tip, 0.0mm, 1.0mm, and 2.0 mm, respectively, to 33.0+/-1.4 degrees C, 63.4 +/- 7.0 degrees C, 57.1+/-5.8 degrees C, 49.9+/-5.8 degrees C+ at 20W with 0.5 ml/sec flow (*p<0.01, +p = 0.09). The lesion volumes were 79.6mm3 for 20W without flow, 64.1 mm3 for 20W with 0.3 ml/sec flow, 47.5 mm3 for 20W with 0.5 ml/sec flow, and 28.6 mm3 for temperature control. CONCLUSIONS: We conclude that 1) the temperature profile greatly depends upon the rate of saline flow for cooling; 2) at high flow rates, the 0.0 mm and 1.0 mm temperatures are similar; 3) even at high irrigation rates, lesion size is greater than for temperature control; 4) the tip temperature significantly underestimates the surface temperature and improved methods of measuring temperature are needed.

Assessment of atrioventricular nodal physiology in the mouse.

Transgenic mice are increasingly being utilized for understanding cardiac electrophysiologic abnormalities. However, little is known about the normal atrioventricular nodal and infraHisian physiology in the mouse because of the prior inability to record a His-bundle deflection. We present the first comprehensive examination of the murine atrioventricular nodal and His-Purkinje systems employing His-bundle recordings. Normal, healthy, male C57BL/6J mice (n = 48) underwent an in vivo electrophysiology study using a 2 F octapolar electrode catheter. Effective refractory periods were determined during premature atrial and ventricular stimulation. The PR interval measured 44 +/- 6 ms with a mean sinus cycle length of 185 +/- 42 ms. Baseline AH intervals were 36 +/- 5 ms and HV intervals were 10 +/- 2 ms. At a pacing cycle length of 140 ms the atrioventricular nodal effective refractory period (AVNERP) and atrial effective refractory period (AERP) were 86 +/- 19 ms and 57 +/- 17 ms, respectively. The mean AV Wenckebach and 2:1 paced cycle length were 103 +/- 14 ms and 84 +/- 13 ms, respectively. Premature atrial stimulation curves were asymptotic without discontinuity. A subset of nine mice was studied after administration of isoproterenol. The sinus cycle length, AVNERP and AERP decreased significantly from baseline measurements. This method establishes a practical and feasible technique to record in vivo His-bundle electrograms in the mouse to assess atrioventricular nodal and infraHisian physiology. Use of this model will allow for the examination of abnormalities of atrioventricular nodal and infraHisian conduction in transgenic murine models.

Cardiac conduction abnormalities in a mouse model of Lyme borreliosis.

BACKGROUND: Borrelia Burgdorferi (BB) induces cardiac conduction abnormalities in infected humans. Mice models of Lyme disease have been developed, however their electrophysiologic (EP) properties of conduction are unknown. METHODS: Seventy-six C3H/J mice (BB infected and age- and gender-matched controls) underwent blinded in vivo EP studies. In a first phase of the study, 40 male C3H/J mice were divided into 2 groups: Group (A) mice were infected at age 3 (weeks) and studied at 5, and Group (B) mice were infected at 9 and studied at 11. In a second phase, 36 female mice were divided into 2 groups: Group (C) mice were infected at 3 weeks and studied at 5, and Group (D) mice were infected at 3 and studied at 11. RESULTS: Infected mice of group (A) and (C) had wider QRS complexes (21.0+/-1.6 versus 17.3+/-1.3ms, p< or =0.0001 and 20.3+/-2.1 versus 18.5+/-1.7, p = 0.05, respectively) compared to the healthy controls (HC). Infected mice of group (B) and group (D) were similar to the HC. In all groups, the presence of conduction abnormalities correlated very closely with the amount of inflammation on pathology. CONCLUSION: This study describes the first EP mouse model of Lyme carditis. C3H/J mice exhibit conduction abnormalities that are reversible 8 weeks after inoculation, closely paralleling the resolution of inflammation on pathology. This model can be a valuable tool in the developing and testing of new modalities for the prevention and treatment of Lyme carditis.

Arrhythmogenic right ventricular dysplasia: clinical results with implantable cardioverter defibrillators.

Arrhythmogenic right ventricular dysplasia is a clinical entity characterized by fatty infiltration of the right ventricle and left bundle morphology ventricular tachycardia occurring in young patients. The most common cause of death is tachyarrhythmic. Pharmacological and nonpharmacological therapies, including implantable cardioverter defibrillators, have been used to treat the arrhythmias. However, right ventricular endocardial leads in this population may be associated with an increased risk of perforation and suboptimal sensing and defibrillation efficacy due to the diseased right ventricle. We report on 12 patients with arrhythmogenic right ventricular dysplasia who were treated with implantable cardioverter defibrillators. The mean age was 31 +/- 9 years (range 15-48). Patients presented with presyncope (5), syncope (4), or cardiac arrest (3). All patients had electrocardiographic abnormalities characteristic of the condition. During programmed electrical stimulation nine patients had sustained ventricular tachycardia, while three patients had no inducible arrhythmia. Transvenous leads were placed in nine patients. In these patients pacing thresholds were significantly higher, R-wave amplitudes were significantly lower and defibrillation thresholds were not significantly different than in a cohort of patients without right ventricular dysplasia. There were no acute or chronic complications of right ventricular lead placement. Follow-up averaged 22 +/- 13 months (range 1-45). There was one sudden death at 1 month of follow-up. Of the 12 patients, 8 have had appropriate therapy delivered by the implantable defibrillator. Six patients are currently on sotalol to reduce the frequency of implantable defibrillator discharges. In conclusion, implantable cardioverter defibrillators with nonthoracotomy leads are feasible and safe in patients with arrhythmogenic right ventricular dysplasia. The frequency of appropriate therapy is high, supporting the use of implantable cardioverter defibrillators in this population.

Combined radiofrequency ablation-cooling catheter for reversible cryothermal mapping and ablation.

Reversible cryothermal mapping of cardiac arrhythmias has been performed intraoperatively. However, a steerable cooling catheter for reversible mapping has not yet been developed. We therefore developed and tested a cooling system consisting of a -15 degrees C hypertonic saline reservoir and a 7F steerable catheter also capable of radiofrequency (RF) ablation. Using excised ovine hearts placed in a 37 degrees C circulating saline bath, we measured the temperatures at depths of 0 mm, 1 mm, and 2 mm. The temperature after 90 seconds of cooling was 16.5 +/- 2.1 degrees C at 0 mm compared to 23.9 +/- 4.1 degrees C at 1 mm and 31.1 +/- 3.9 degrees C at 2 mm depth (p < 0.01). These data suggest that a 7F steerable combined RF ablation-cooling catheter may achieve temperatures suitable for mapping arrhythmias such as atrial tachycardias and right ventricular outflow tract tachycardias. Further enhancements to achieve lower temperatures at depth may be needed to reversibly map other arrhythmias such as left ventricular tachycardias.

Cardiac arrhythmias in the athlete.

Cardiac arrhythmias in the athlete are a frequent cause for concern. Some arrhythmias may be benign and asymptomatic, but others may be life threatening and a sign that serious cardiovascular disease is present. Physicians often are consulted with regard to arrhythmias, or symptoms consistent with arrhythmias, in athletes. Sinus bradyarrhythmias are common and even expected in athletes. These bradyarrhythmias are rarely a cause for concern. Heart block is unusual and merits a thorough workup. Atrial fibrillation may be more common in the athlete. Supraventricular tachycardias other than atrial fibrillation generally warrant consideration of radiofrequency ablation for cure of the tachyarrhythmia. Ventricular arrhythmias in the athlete generally occur in the setting of structural heart disease that is genetically determined (hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, anomalous coronary arteries) or acquired (coronary artery disease, myocarditis, idiopathic dilated cardiomyopathies). In these conditions, the arrhythmia generally is life threatening. Ventricular arrhythmias that occur in the athlete without structural heart disease are not thought to be life threatening. Athletes with structural heart disease and syncope and those with exertional syncope merit a complete evaluation.

A new platinum balloon-expandable stent (Angiostent) mounted on a high pressure balloon: acute and late results in an atherogenic swine model.

BACKGROUND: Randomized studies have proven the efficacy and safety of stent placement to treat de novo coronary stenosis. However, the poor radio-opacity and the use of an additional high-pressure balloon to fully expand the stent are the major limitations of the currently clinically-approved stents. OBJECTIVE: We evaluated the safety, efficacy, angiographic and histologic effect of a new platinum balloon expandable stent mounted on a high-pressure balloon in Yucatan miniature swine fed high cholesterol diet. METHODS: Fifteen Angiostents (NuMED, Inc., Hopkinton, NY and Angiodynamics, Glens Falls, NY) (coronary stent was 3, 3.5, or 4 mm in diameter and 12 mm long; renal and carotid stents were 5 mm in diameter and 13 mm long) mounted on a high-pressure balloon were placed percutaneously in blood vessels of 10 pigs [5 in circumflex (CX), 2 in left anterior descending (LAD), 5 in renal and 3 in carotid arteries]. The stent was 10-20% larger than the native vessel diameter. All animals received 5000 I.U. of heparin during the procedure and were maintained on 325 mg aspirin daily. Follow-up angiography and histology in the animals was performed at 2, 4, 12, 20, 26 and 52 weeks. RESULTS: The stents were easily visualized with fluoroscopy and placed in all animals without episodes of balloon rupture or embolization. There was no episode of acute thrombosis. Follow-up angiography in the animals revealed patency of all renal and carotid stents, however, 2/7 coronary stents in the animals revealed angiographic lumen narrowing (> 20%) at 20 and 52 weeks. Histologic examination revealed neointimal formation at the stent site with an average neointimal thickness ranging from 325-650 microns. CONCLUSION: This stent was safe in this animal model, easily deployed, had excellent radio-opacity and with good short-term patency without anticoagulation. Clinical trials and experience is underway.

Predictors of ventricular tachycardia recurrence in 100 patients receiving tiered therapy defibrillators.

BACKGROUND AND HYPOTHESIS: Programmed electrical stimulation (PES) is a time-honored diagnostic tool in patients with ventricular tachyarrhythmias. The response to PES can be used to assess efficacy of pharmacologic or electrical therapy, as well as to obtain prognostic information. Reproducible induction of ventricular tachycardia with invasive electrophysiologic testing, or stimulation through defibrillator lead systems, can help optimize antiarrhythmic drug therapy and device programming during clinical follow-up. METHODS: We present our experience with 100 patients who had inducible sustained monomorphic ventricular tachycardia (SMVT) during invasive PES at baseline, and received a third-generation implantable cardioverter-defibrillator (ICD) alone, or in combination with antiarrhythmic drug therapy. Noninvasive programmed stimulation (NIPS) was performed prior to hospital discharge in 61 patients. RESULTS: The inducibility of SMVT was concordant between the invasive study and NIPS in a subgroup of 40 (82%) patients who had invasive PES on the same drug regimen. During a mean follow-up of 16 months, there were 12 nonarrhythmic deaths and recurrence of spontaneous SMVT in 36 (40%) of the surviving patients. Using a Cox proportional hazards model, the following variables were associated with early arrhythmia recurrence: persistent inducibility of SMVT during the NIPS session (relative risk 11, range 2.6-47); induction of SMVT with a cycle length > 280 ms during invasive baseline PES (2.5, 1.2-5) and presence of prior inferior myocardial infarction (2.1, 1-4.2). Timing to initial recurrence of spontaneous tachycardia was unaffected by other clinical variables or concomitant antiarrhythmic drug use. CONCLUSION: Programmed electrical stimulation techniques offer insight into the patterns of spontaneous ventricular tachycardia recurrence and have significant practical utility in the management of patients receiving third-generation ICDs.

Strategies for managing atrial fibrillation.

The limitations of current therapies for atrial fibrillation are forcing a rethinking of how they should be used. Questions are being raised about the use of antiarrhythmic drugs, and new nonpharmacologic procedures are promising alternatives. Most patients with atrial fibrillation still require warfarin therapy, but some low-risk patients can forego it. Sinus rhythm spontaneously returns within the first 24 hours in almost half of cases of new atrial fibrillation. Patients with hemodynamic instability due to new-onset atrial fibrillation should proceed directly to electrical cardioversion. Warfarin therapy to maintain an International Normalized Ratio (INR) of 2.0 to 3.0 is currently recommended for all patients with atrial fibrillation with no contraindications to it, except for patients younger than 60 years with lone atrial fibrillation, in whom the risk of stroke is low. Certain antiarrhythmic drugs should be avoided in patients with congestive heart failure, in whom the risks may exceed the benefits. The maze procedure is emerging as an option to restore and maintain sinus rhythm. Radiofrequency atrioventricular node ablation and modification hold promise as options to control the ventricular rate without drugs.

ECG Findings in Active Patients: Differentiating the Benign From the Serious.

ECGs and cardiac rhythms of normal athletes can vary widely. The heightened vagal tone from athletic conditioning can result in variant ECG findings that may mimic serious disorders. ECG patterns of long-QT syndrome, arrhythmogenic right ventricular dysplasia, Wolff-Parkinson-White syndrome, and hypertrophic cardiomyopathy signal the need for further evaluation, therapy, and possible participation restriction. Radiofrequency ablation may be appropriate when symptomatic supraventricular arrhythmias or Wolff-Parkinson-White syndrome is present. Further research is needed to effectively distinguish normal ECG changes in the athlete from changes that underlie cardiac disease. Improvements in identifying athletes at risk of serious or life-threatening arrhythmias are also needed.

Serological and molecular capsular typing, antibiotic susceptibility of Streptococcus pneumoniae isolates from invasive and non-invasive infections.

Streptococcus pneumoniae causes life threatening infections and necessitate for impediment and controlling disease; to conquer this, information is needed about serotype distribution and patterns of antibiotic resistance. The present study was to determine the serotype distribution of S. pneumoniae isolated from the entire age group individual and to correlate this distribution with susceptibility. Cases of pneumococcal infections have been reviewed for serotyping and antibiotic susceptibility. Out of 117 pneumococcal isolates 45 (39%) were penicillin-resistant, 84 (72%) were erythromycin-resistant and 100% were co-trimoxazole resistant. The most frequently isolated serotypes were 23F, 19F, 14, 6B, 5, 6A, 19A and 9V. PCV7, PCV10 and PCV13 coverage was 68%, 79%, 87%, respectively. Similarly, there was similarity in PCV7 coverage for non invasive isolates (64.5%) and invasive isolates (72.2%). The study state that common pneumococcal serotypes were present in similar ways as reported in literature. A continuous survey of pneumococcal infected population is requirement and necessity for success of vaccination.

Prevalence of 16S rRNA methylase genes among ß-lactamase-producing Enterobacteriaceae clinical isolates in Saudi Arabia.

BACKGROUND: Co production of 16S rRNA methylases gene and ß-Lactamase gene among Enterobacteriaceae isolates conferring resistance to both therapeutic options has serious implications for clinicians worldwide. METHODS: To study co existence of 16S rRNA methylases (armA, rmtA, rmtB, rmtC, rmtD, and npmA) and ß-Lactamase (blaTEM-1, blaSHV-12, blaCTX-M-14) genes, we screened all phenotypic positive ß-Lactamase producing enterobacteriaceae by polymerase chain reaction (PCR) targeting above genes. A total of 330 enterobacteriaceae strains were collected during study period out of that 218 isolates were identified phenotypically as ß-Lactamase producers, which include 50 (22.9%) Escherichia coli; 92 (42.2%) Klebsiella pneumoniae, 44 (20.2%), Citrobactor freundii and 32 (14.7%) Enterobacter spp. RESULTS: Among this 218, only 188 isolates harbored the resistant gene for ß-Lactamase production. Major ß-Lactamase producing isolates were blaTEM-1 type. 122 (56 %) isolates were found to produce any one of the 16S rRNA methylase genes. A total of 116 isolates co produced b-Lactamase and at least one 16S rRNA methylases gene Co production of armA gene was found in 26 isolates with rmtB and in 4 isolates with rmtC. The rmtA and rmtD genes were not detected in any of the tested isolates. Six isolates were positive for a 16S rRNA methylase gene alone. CONCLUSION: ß-Lactamase producing isolates appears to coexist with 16S rRNA methylase predominantly armA and rmtB genes in the same isolate. We conclude the major ß-Lactamase and 16S rRNA methylases co-producer was K. pneumoniae followed by E. coli. We suggest further work on evaluating other ß-lactamases types and novel antibiotic resistance mechanisms among Enterobacteriaceae.