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Biomedical subjects

P C Nalos

Publications and source records attributed to P C Nalos.

13 recordsLinked to original sources
PubMed1991

Prospective community evaluation of the signal-averaged electrocardiogram in predicting malignant ventricular arrhythmias: beneficial outcome with electrophysiology guided therapy.

The role of the signal-averaged ECG was prospectively assessed in 517 patients in whom there was a suspicion for malignant ventricular arrhythmias. Patients were divided into Group I with a normal surface QRS width less than 120 ms (426 patients) and Group II with a prolonged QRS duration greater than or equal to 120 ms (91 patients). Late potentials were present in 42 (10%) Group I patients and in 24 (26%) Group II patients. Programmed ventricular stimulation was performed for standard indications in 55 patients without late potentials and in 42 patients with late potentials, combining both groups. The sudden death or recurrent sustained ventricular tachycardia rate in follow-up was evaluated based on the presence or absence of late potentials and whether programmed ventricular stimulation was performed. In the patients without late potentials, these rates were 4 patients (1.0%) in the no EP group and 3 patients (5.5%) in the EP group (p less than .05), respectively (overall 1.6%). In the patients with late potentials, these rates were 7 patients (29%) in the no EP group and 7 patients (17%) in the EP group (p = .19), respectively (overall 21%). In addition, appropriate automatic defibrillator shocks were present in 1 patient without late potentials and in 8 patients with late potentials which were not included in the recurrent sudden death or sustained ventricular tachycardia statistics. The signal-averaged ECG accurately defines patients at a higher risk for malignant ventricular arrhythmias regardless of unfiltered QRS duration.(ABSTRACT TRUNCATED AT 250 WORDS)

Electric Countershock↗
PubMed1991

Intravenous amiodarone for short-term treatment of refractory ventricular tachycardia or fibrillation.

Intravenous amiodarone was administered to 22 patients with recurrent ventricular tachycardia failing an average of 3.0 prior antiarrhythmic agents after a mean of 14.6 cardioversions per patient. Patients received a mean bolus of 239 mg amiodarone, and a constant infusion of 0.5 to 1.0 mg/ml was administered over a mean of 50.7 hours. Hypotension requiring pressor agents was seen in nine patients and temporary pacing was needed in five patients. In the hospital, arrhythmic deaths occurred in two (9%) patients and nonarrhythmic deaths occurred in six (27%) patients. There were three late sudden deaths and three additional patients with appropriate automatic defibrillator discharges in follow-up. Intravenous amiodarone is very effective in preventing arrhythmic deaths in patients with refractory ventricular tachycardia and fibrillation.

Aged↗
PubMed1990

Benefit and risks of long-term amiodarone therapy for sustained ventricular tachycardia/fibrillation: minimum of three-year follow-up in 145 patients.

Our experience with amiodarone therapy in 145 consecutively referred patients with medically refractory sustained ventricular tachycardia and/or fibrillation treated for at least 3 years was reviewed. Ninety-seven had sustained ventricular tachycardia; the remaining 48 patients were survivors of sudden cardiac death. The patients had a mean of 3.7 +/- 1.4 unsuccessful anti-arrhythmic drug trials before initiation of amiodarone. The initial doses of amiodarone averaged 845 +/- 258 mg for the first 2 weeks and 56% of all patients received a type I antiarrhythmic drug in addition to amiodarone during the initial phase of therapy. The average maintenance dose of amiodarone was 410 +/- 187 mg per day. All patients were followed for a minimum of 3 years or until death or withdrawal from therapy. The maximum follow-up was a period of 8 years. Thus, the average duration of amiodarone therapy was 39 +/- 26 months, representing 472 patient years of therapeutic time on amiodarone. The incidence of deaths either caused by a documented ventricular tachyarrhythmia or presumed to result from an arrhythmic cause was 5.5% in the first year and 3.4% in each of the second and third years of follow-up. During the entire period of follow-up, 56 patients died of all causes (38.6% of the study population). Survival over the follow-up period was influenced significantly by left ventricular function, as judged by either New York Heart Association Functional Class or objective assessment of left ventricular ejection fraction, which was available in 102 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Benefits of intracardiac electrograms and programmable sensing polarity in preventing pacemaker inhibition due to spurious screw-in lead signals.

False inhibition of ventricular output due to spurious signals from a bipolar Oscor Medical lead (PY58BV) is reported following implantation of a Pacesetter Synchrony DDDR 2020T. Telemetered bipolar and distal unipolar intracardiac electrograms revealed 20 mV spurious signals coming from the distal screw-in electrode. Reprogramming the sensing channel to unipolar ring prevented inhibition of pacemaker output.

Aged↗
PubMed1988

Utility of the signal-averaged electrocardiogram in patients presenting with sustained ventricular tachycardia or fibrillation while on an antiarrhythmic drug.

The utility of the signal-averaged electrocardiogram (SAECG) for predicting ventricular tachycardia (VT) induction in patients presenting with sustained VT or ventricular fibrillation (VF) while on an empirically chosen antiarrhythmic agent was assessed in 17 patients. At the time of presentation with a malignant arrhythmia, 12 patients were taking quinidine, three patients were taking procainamide, and two patients were taking flecainide. All patients underwent programmed ventricular stimulation when not taking antiarrhythmic drugs; 12 patients had no inducible sustained VT and five patients had inducible sustained monomorphic VT. The SAECG done in the control state without antiarrhythmic agents was negative for late potentials in 11 of 12 patients in the noninducible group and positive for late potentials in four of five patients in the inducible group (sensitivity = 80% and specificity = 92%). We conclude that in patients presenting with life-threatening ventricular arrhythmias while taking an antiarrhythmic drug, the SAECG distinguishes patients with possible proarrhythmic events from those who have the substrate for inducible sustained VT.

Adult↗
PubMed1988

Subthreshold atrial pacing in patients with a left-sided accessory pathway: an effective new method for terminating reciprocating tachycardia.

This study investigated the possibility of terminating reciprocating atrioventricular (AV) tachycardia using subthreshold atrial pacing. Ten patients with a left-sided accessory pathway and sustained AV tachycardia underwent subthreshold atrial pacing from the coronary sinus site closest to insertion of the accessory pathway. In seven of these patients, the tachycardia could be reliably terminated with subthreshold atrial overdrive pacing. When pacing at a cycle length of 80 +/- 23% of the tachycardia cycle length, the minimal subthreshold current that was effective in tachycardia termination was 64 +/- 14% of threshold current and the maximal ineffective current was 49 +/- 17% of threshold (p less than 0.05). In all cases, the tachycardia was terminated by one or two instances of atrial capture that resulted in a premature atrial impulse (20 +/- 4% advancement of the atrial cycle) that blocked the AV node limb of the tachycardia. Anterograde conduction over the accessory pathway never occurred, either during the tachycardia or during subthreshold pacing after a return to normal sinus rhythm. No instances of atrial fibrillation were provoked by subthreshold pacing. Possible explanations for the intermittent atrial capture with critically placed subthreshold impulses include supernormal atrial conduction or summation of impulses at the atrial insertion site of the accessory pathway. It is concluded that subthreshold pacing is effective in selected patients with AV tachycardia due to an accessory pathway. Furthermore, because neither atrial fibrillation nor anterograde conduction over the accessory pathway is seen with subthreshold pacing, this modality may hold significant promise for permanent antitachycardia pacing in these patients.

Adult↗
PubMed1988

Electrical safety during electrophysiological testing.

This report describes the inadvertent induction of non-sustained atrial and ventricular arrhythmias due to the malfunction of a programmable cardiac stimulator. The malfunction occurred when line power resumed after a brief municipal power outage ("blackout") during an invasive electrophysiological study. The stimulator spontaneously delivered very high frequency pulses through the electrode catheter to the myocardium which resulted in atrial and ventricular arrhythmias. During bench testing, the stimulator delivered a continuous train of high frequency output pulses (greater than or equal to 1 mA) when line voltage resumed normal level after it had dropped below 65 VAC. Electrical safety during electrophysiological testing requires a stimulator design which is immune to altered operating conditions, and which shuts down if abnormal operating or output conditions are detected.

Arrhythmias, Cardiac↗
PubMed1987

The signal-averaged electrocardiogram as a screening test for inducibility of sustained ventricular tachycardia in high risk patients: a prospective study.

The role of the signal-averaged electrocardiogram in predicting the induction of sustained monomorphic ventricular tachycardia in high risk patients was assessed prospectively in 100 consecutive patients. Presenting diagnoses were syncope (38 patients), nonsustained ventricular tachycardia (24 patients), sustained ventricular tachycardia (25 patients) and sudden cardiac arrest (13 patients). Using programmed ventricular stimulation, 71 patients (group I) did not have and 29 patients (group II) did have inducible sustained monomorphic ventricular tachycardia. Using the signal-averaged electrocardiogram with filtering (6 dB/octave) at high pass corner frequencies of 67 and 100 Hz, the two groups were compared. The signal-averaged electrocardiogram was considered abnormal if all of the following criteria were satisfied: 1) the total filtered QRS complex duration was greater than 120 ms, 2) the duration of the terminal QRS complex of less than or equal to 20 microV was greater than or equal to 30 ms, and 3) at least one deflection (late potential) was present in this region. Differences between groups I and II in these three measures were highly significant (p less than or equal to 0.001). The sensitivity and specificity of signal averaging for predicting the induction of sustained ventricular tachycardia were 93 and 94%, respectively. Stepwise logistic regression analysis identified the signal-averaged electrocardiogram as the best predictor of induction of sustained monomorphic ventricular tachycardia, independent of left ventricular ejection fraction, presence of ventricular aneurysm, myocardial infarction and other clinical variables (chi-square = 93.2, p less than 0.0001). The signal-averaged electrocardiogram is a sensitive and specific test for the induction of sustained monomorphic ventricular tachycardia, having independent predictive value.

Coronary Disease↗
PubMed1987

Intermittent fascicular extrasystoles producing pseudo AV block: electrophysiologic effects of beta agonists and antagonists.

This report describes a patient with pseudo-type II second-degree AV block due to an intermittent parasystolic focus located in the left bundle branch. A paradoxical increase in the fascicular rate was seen following intravenous propranolol, and fascicular extrasystoles were suppressed after intravenous isoproterenol treatment. All propagated fascicular extrasystoles were conducted to the ventricle with incomplete or complete right bundle branch block and a decrease in the H'-V interval compared to the H-V interval during sinus rhythm. Treatment with oral quinidine abolished fascicular extrasystoles without worsening of AV conduction.

Bundle-Branch Block↗
PubMed1987

Orthodromic tachycardia initiation dependent on 1:2 atrioventricular conduction in the presence of a left lateral bypass tract.

This report describes a patient who presented with atrial fibrillation associated with a rapid ventricular response (270 bpm) and wide QRS complexes. At the time of electrophysiology study, a left lateral bypass tract with both anterograde and retrograde conduction was demonstrated. Orthodromic tachycardia with atrial premature impulses was initiated and was dependent on two ventricular responses to one atrial impulse. Intravenous procainamide administration had little effect on anterograde or retrograde conduction in the accessory pathway; however, it prevented orthodromic tachycardia initiation with atrial premature impulses by prolonging atrial muscle refractoriness.

Adult↗
PubMed1987

Life-threatening postoperative pulmonary complications in patients with previous amiodarone pulmonary toxicity undergoing cardiothoracic operations.

Amiodarone therapy for cardiac arrhythmias is increasingly being recognized to be associated with pulmonary toxicity. In this report, we describe the case histories of four patients with previously diagnosed amiodarone pulmonary toxicity in whom the adult respiratory distress syndrome developed after cardiothoracic operations for malignant ventricular arrhythmias. Three patients underwent endocardial resection (two died), and a fourth patient had implantation of an automatic defibrillator unit. Radiographic changes and results of pulmonary function testing are evaluated during initial toxicity and preoperatively. These four patients (mean amiodarone dosage of 420 mg/day for 20 months) are compared to 13 other patients undergoing cardiothoracic operations with prior amiodarone treatment (one patient with preoperative pulmonary toxicity) in whom life-threatening postoperative pulmonary complications did not develop (mean dosage of 550 mg/day for 10 months). Mean preoperative serum amiodarone levels for the four patients were 1.5 micrograms/ml. In the two patients who died, desethylamiodarone levels were 510 and 4,400 micrograms/gm in pulmonary tissue. Histologic examination showed "honeycomb" appearance of the lung with prominent septae, alveolar foamy macrophages, and hyperplasia of alveolar lining cells, consistent with amiodarone pulmonary toxicity. Causes including pump-oxygenator time, oxygen toxicity, anesthetic agents, congestive heart failure, and pulmonary infection superimposed on amiodarone pulmonary toxicity are discussed with a review of the literature.

Aged↗
PubMed1986

Hemodynamic influences on sinus node recovery time: effects of autonomic blockade.

Ten patients with normal sinus node function were evaluated prospectively, to determine whether the decrease in blood pressure during rapid atrial pacing shortens the corrected sinus node recovery time. All patients had 30 seconds of atrial pacing at cycle lengths from 600 to 300 ms, with continuous arterial pressure monitoring, before and after intravenous administration of propranolol (0.2 mg/kg body weight) and atropine (0.04 mg/kg). In the control state, a decrease in corrected sinus node recovery time was recorded with faster atrial pacing rates, which was significantly related to the initial drop in systolic blood pressure at the onset of atrial pacing. Specifically, as the initial pressure drop increased from 15 mm Hg or less to 16 to 45 and 45 to 100 mm Hg, corrected sinus node recovery time decreased from 272 +/- 79 to 205 +/- 70 ms (p less than 0.04) and to 134 +/- 120 ms (p less than 0.04), respectively. In contrast, after autonomic blockade, the corrected sinus node recovery time was prolonged, in a near linear fashion, as atrial pacing rates increased. The magnitude of blood pressure drop with atrial pacing did not differ significantly from that in the control state at similar pacing rates. These findings suggest that hypotension during rapid atrial pacing activates autonomic reflexes that significantly shorten the corrected sinus node recovery time. Autonomic blockade negates this effect and the corrected sinus node recovery time prolongs with faster atrial pacing.

Adult↗