Comparison of the haemodynamic effects of right ventricular outflow-tract pacing with right ventricular apex pacing: a quantitative review.

The right ventricular apex has been used for cardiac stimulation because this position is easily accessible and is associated with a stable position of the electrode with a low dislodgement rate. This position, however, is associated with a dyssynchronous left ventricular contraction with subsequent deleterious haemodynamic effects. Alternative stimulation sites have been studied extensively because of a potentially better haemodynamic effect compared with right ventricular apex pacing. Using a Cochrane search strategy, nine studies were selected to analyze the haemodynamic effects of right ventricular outflow-tract pacing. The results of these studies (n=217) were pooled and indicated a significantly better haemodynamic effect (odds ratio 0.34, confidence interval 0.15-0.53) compared with right ventricular apex pacing. Therefore, these data suggest that right ventricular outflow-tract pacing may offer a modest but significant benefit over right ventricular apex pacing in patients selected for pacemaker implantation on the basis of symptomatic bradyarrhythmias.

Experience with a cosmetic approach to device implantation.

As more young patients are having device implantations, we need to be more concerned with appearance and function. Over a 20-month period pacemakers and defibrillators were implanted in 14 women (mean age 49 years) using a two-incision technique that leaves no visible scars on the chest.

Experience with a higher impedance, fixed helix, steroid-eluting pacing lead. The SWEET PICOTIP Rx Study Group.

A higher impedance, steroid-eluting pacing lead was studied in a multicenter trial. A total of 132 leads were implanted in 61 patients and the electrical characteristics were compared with historical controls. The study lead had a lower pacing threshold at 3 months, 0.72 +/- 0.33 versus 1.29 +/- 0.82 in the atrium and 0.71 +/- 0.25 versus 1.52 +/- 0.52 in the ventricle (P < 0.01 for both). Impedance was significantly higher in the study lead, 923 +/- 133 versus 719 +/- 109 in the atrium and 980 +/- 235 versus 664 +/- 104 in the ventricle (P < 0.01 for both). Sensing was similar for both leads. The study lead's higher impedance values and low pacing thresholds combine to reduce pacing system energy requirements.

Mode switching anomalies: a patient who remained symptomatic during paroxysmal atrial tachyarrhythmias despite a mode switching pacemaker.

A patient with an automatic mode switching pacemaker continued to experience discomfort during the onset of paroxysmal supraventricular tachyarrhythmias. Investigation revealed that the patient was sensing abrupt rate changes as the ventricular paced rate tracked the tachycardia during onset and detection phases. Her pacemaker was replaced with a new device with both mode switching and rate smoothing capabilities with resultant elimination of symptoms.

Comparison of right ventricular outflow tract and apical lead permanent pacing on cardiac output.

Cardiac output was measured in 89 patients using transthoracic continuous-wave echo Doppler comparing right ventricular outflow tract pacing with the right ventricular apex at the time of permanent pacemaker implantation. Overall, cardiac output improved 18.8% (p <0.0001) and cardiac index 21.0% (p <0.0001) with outflow tract placement; patients with a lower baseline cardiac index had a greater percent improvement with outflow tract placement.

Complete atrioventricular block due to large cell lymphoma: resolution with chemotherapy.

Malignant lymphoma commonly involves the heart. Previous studies have found cardiac metastases in up to 20% of patients dying with lymphoma. Cardiac signs and symptoms of lymphoma are relatively rare, however, and in most cases, the diagnosis is made either postmortem or too late to affect the clinical course. This report presents the first case of complete heart block due to lymphoma that responded to surgery and chemotherapy with return of normal atrial ventricular conduction.

Narrow-complex tachycardia.

The term "narrow-complex tachycardia" is applied to a number of common and rare arrhythmias. Atrial fibrillation is the narrow-complex tachycardia most frequently seen in clinical practice. Sinus tachycardia is associated with underlying metabolic abnormalities, and paroxysmal atrial tachycardia most often results from digitalis toxicity. Multifocal atrial tachycardia usually occurs in older adults with chronic obstructive pulmonary disease. Atrioventricular nodal reentrant tachycardia is commonly found in otherwise healthy children and adolescents. The initial diagnosis should be reconsidered if drug therapy is unsuccessful, because differences in rhythm disturbances are often subtle. Radiofrequency catheter ablation is an effective treatment for atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia (Wolff-Parkinson-White syndrome) and the permanent form of junctional reentrant tachycardia. Catheter ablation should also be considered in difficult cases of atrial flutter, intra-atrial reentry and automatic atrial tachycardia.

Radiofrequency catheter ablation of an intraatrial reentrant tachycardia: evidence of an area of slow conduction.

Radiofrequency catheter ablation for intraatrial reentrant tachycardia has not been previously reported. This article describes a patient with a demonstrable area of slowed conduction in the lateral right atrium that responded to radiofrequency catheter ablation in the area of the fractionated electrogram with elimination of the tachycardia. This patient also had the common form of atrioventricular nodal reentrant tachycardia, which was also successfully ablated.

Intraoperative myocardial infarction during open-heart ablation of an atrioventricular accessory pathway.

We report a patient who suffered an intraoperative AMI from injury to the distal portion of a dominant left circumflex coronary artery in the atrioventricular groove. Depending upon coronary anatomy and location of accessory pathways, compromise of coronary circulation by nonintrinsic pathology can be a major cause of morbidity.

Incidence of electrocardiographic changes during cesarean delivery under regional anesthesia.

Serial electrocardiograms were obtained on 93 healthy ASA physical status I and II term parturients during nonemergent cesarean delivery under regional anesthesia. Electrocardiographic changes occurred in 44 of the 93 patients (47.3%); in 35 of these 44 patients, the changes were characteristic, or suggestive, of myocardial ischemia. Symptoms of chest pain, pressure, and dyspnea occurred in 15 of the 44 patients with electrocardiographic changes; no patient without electrocardiographic change developed symptoms of chest pain, pressure, or dyspnea. Small but statistically significant differences were noted in heart rate, diastolic and systolic arterial pressures, and rate-pressure product between the patients with electrocardiographic changes and those without. The authors speculate that myocardial ischemia is a likely cause of both the electrocardiographic changes seen in these patients and of the symptoms of chest pain and dyspnea that they sometimes experience.