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Biomedical subjects

F Morady

Publications and source records attributed to F Morady.

At least 253 records · Page 14Linked to original sources
PubMed1990

Cost of catheter versus surgical ablation in the Wolff-Parkinson-White syndrome.

In this retrospective study of 22 patients with the Wolff-Parkinson-White (WPW) syndrome, the cost of catheter ablation in 11 patients was compared with that of surgical ablation in another 11 patients. All patients in the catheter ablation group had a posteroseptal accessory pathway; in the surgical group, 5 patients had a left lateral accessory pathway, 3 had a left lateral and posteroseptal accessory connection and 3 had a right-sided pathway. Catheter ablation was successful in 8 of 11 patients (73%). In the surgical group, the accessory pathway was interrupted successfully in all patients (100%). The mean duration (+/- standard deviation) of hospitalization was 6 +/- 2 days in the catheter ablation group and 8 +/- 4 days in the surgical group. The mean cost/patient, expressed in 1988 dollar values, was +14,116 +/- 4,493 in the catheter ablation group and +34,175 +/- 5,434 in the surgical ablation group (p less than 0.0001). The mean time lost from work or school was 10 +/- 5 days in the catheter ablation group and 60 +/- 16 days in the surgical group (p less than 0.01). Catheter ablation is significantly less expensive than surgical ablation of accessory pathways. Assuming that all patients in whom catheter ablation is unsuccessful subsequently undergo successful surgical ablation, the mean cost of definitive therapy in the catheter ablation group (+24,382 +/- 4,741) is still significantly lower than the cost in the surgical group (+34,175; p less than 0.001). An additional economic advantage of catheter ablation is that the mean time lost from work or school is 10 days compared to 60 days with surgical ablation.

Adolescent↗
PubMed1990

Acute changes in pacing threshold and R- or P-wave amplitude during permanent pacemaker implantation.

This study examines the changes in pacing threshold and R- or P-wave amplitude during the first 30 minutes after implantation of tined and screw-in leads. The leads examined were those of 1 manufacturer (Medtronic) and consisted of 3 ventricular pacing leads (model numbers 6957 unipolar screw-in [11 patients], 6961 unipolar tined [12 patients] and 6962 bipolar tined [7 patients]) and 1 atrial lead (model number 6957J unipolar screw-in [10 patients]). After optimal lead position was obtained fluoroscopically in the right ventricular apex or right atrium, the pacing threshold and R- or P-wave amplitudes were measured at 5-minute intervals for 30 minutes. The acute ventricular pacing threshold with the screw-in lead was significantly higher than with the tined lead (0.84 +/- 0.17 vs 0.58 +/- 0.15 volts; p less than 0.001). There was a significant (p less than 0.001) acute decrease in the ventricular pacing threshold with both lead types, with the maximum decrease occurring 5 minutes after lead implantation. There was a significant acute increase in R-wave size with the ventricular screw-in lead that peaked 20 minutes after lead implantation (11.9 +/- 3.0 to 14.7 +/- 4.1 mV; p less than 0.001). The atrial screw-in lead behaved in a manner identical to its counterpart in the ventricle. In conclusion, there are acute changes in the pacing threshold and R- or P-wave amplitude obtained with tined and screw-in pacing leads.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Effect of basic drive cycle length on the yield of ventricular tachycardia during programmed ventricular stimulation.

The yield of sustained, monomorphic ventricular tachycardia (VT) induced by programmed ventricular stimulation was compared, using basic drive trains of 400 ms, 600 ms and sinus rhythm, to identify the most efficient sequence of basic drive trains to use during programmed stimulation. Fifty-five patients with coronary artery disease and inducible sustained monomorphic VT not requiring countershock to terminate underwent 81 electrophysiology tests in which 1 to 3 extrastimuli were introduced during sinus rhythm and after basic drive trains of 600 and 400 ms. In 72 electrophysiology tests, sustained, monomorphic VT was induced at the right ventricular apex. The yield of VT using a drive cycle length of 400 ms was 63 of 72 (88%), compared to 46 of 72 (64%) when the drive cycle length was 600 ms, and 23 of 72 (32%) when the extrastimuli were introduced during sinus rhythm (p less than 0.001 for all pairwise comparisons). In 14 electrophysiology tests in which VT was not induced using a 400 ms basic drive cycle length at the apex, the yield of VT was higher using a 400 ms drive cycle length at a second right ventricular site (12 of 14) than with a 600 ms drive cycle length (3 of 12) or sinus rhythm (4 of 12) at the apex (p less than 0.05). The yield of sustained, monomorphic VT induced by 1 to 3 extrastimuli increases as the basic drive cycle length shortens. Whereas programmed stimulation is conventionally started during sinus rhythm or with a drive cycle length of 600 ms, the present results suggest that starting with a drive cycle length of 400 ms may be more efficient.

Cardiac Pacing, Artificial↗
PubMed1990

The effect of ciprofloxacin on the pharmacokinetic and ECG parameters of quinidine.

Ciprofloxacin decreases the clearance of antipyrine and other drugs which, in part, undergo oxidative metabolism. Based on these findings, the authors hypothesized that ciprofloxacin may decrease the clearance of quinidine, a drug which also undergoes oxidative metabolism. The purpose of this study was to evaluate the effect of ciprofloxacin on the pharmacokinetic and ECG parameters of quinidine in seven healthy men. Oral quinidine sulfate 400 mg was administered alone (Phase A) and after oral ciprofloxacin pretreatment (Phase B) in a randomized crossover fashion with a 2-week washout period between each phase. During Phase B, ciprofloxacin pretreatment (750 mg every 12 hours) was administered for 5 days before and 24 hours after quinidine administration. Quinidine serum samples were obtained over a 24-hour period. QRS and QTc intervals were measured over a 12-hour period. There were no significant differences in clearance (20.3 +/- 3.3 L/hr vs 20.1 +/- 2.3 L/hr, P = .836), half-life (7.9 +/- 1 hr vs 7.8 +/- 0.8 hr, P = 0.8), maximum concentration (1.4 +/- 0.6 mg/L vs 1.5 +/- 0.6 mg/L, P = 0.613), or time to maximum concentration (1.5 +/- 0.2 hr vs 1.5 +/- 0.1 hr, P = 0.571) for quinidine between Phase A and Phase B, respectively. The largest decrease in clearance observed for Phase B compared to Phase A was 10%. There was also no significant difference in the degree of QRS and QTc prolongation between Phase A and Phase B. From these results, it appears that ciprofloxacin in the dose given does not alter the pharmacokinetic or ECG parameters of quinidine. Therefore, no adjustment in the dose of quinidine is needed when coadministered with ciprofloxacin.

Adult↗
PubMed1990

Feasibility and cost savings of outpatient electrophysiologic testing.

The feasibility of outpatient electrophysiologic testing was examined by reviewing 100 consecutive outpatient tests performed in 95 patients. Seventy-one of the patients (75%) had no underlying heart disease. The electrophysiologic tests were performed to evaluate supraventricular tachycardias (n = 47), nonsustained ventricular tachycardia (n = 20), unexplained syncope (n = 21), palpitation (n = 9) or intermittent heart block (n = 2). A mean of 2.8 +/- 0.5 6F electrode catheters were inserted through a femoral vein. An electrode catheter was inserted into a subclavian or internal jugular vein in 28 tests and a 5F cannula was inserted into a femoral artery to monitor the blood pressure in 20 tests. The results of 61 tests (61%) were abnormal. Patients were monitored for a mean of 3.8 +/- 1.2 h after the procedure and then discharged. No complications occurred. For cost analysis a subgroup of 60 of these patients was matched for age, gender, heart disease and indication for electrophysiologic testing with a group of 60 patients who underwent electrophysiologic testing as inpatients. Physicians' fees for the two groups were similar; however, the mean hospital charge was $5,845 +/- 3,763 for the inpatient group compared with only $2,120 +/- 1,244 for the outpatient group (p less than 0.001). Thus, outpatient electrophysiologic testing is feasible and safe and results in substantial cost savings in patients without life-threatening arrhythmias.

Adult↗
PubMed1990

Determinants of the ventricular rate during atrial fibrillation.

Determinants of the ventricular cycle length during atrial fibrillation were examined in 52 patients. Thirty-three patients had structural heart disease and none had an accessory atrioventricular (AV) connection. The AV node effective and functional refractory periods, the shortest atrial pacing cycle length associated with 1:1 conduction, the AV node conduction time and indexes of concealed conduction in the AV node were measured in the baseline state (36 patients) and after modification of sympathetic tone by infusion of isoproterenol or propranolol (8 patients each). Atrial fibrillation was then induced with rapid atrial pacing, and the mean, shortest and longest ventricular cycle lengths were measured. Variables that correlated most strongly with the mean RR interval during atrial fibrillation were the AV node effective refractory period (r = 0.93; p less than 0.001), AV node functional refractory period (r = 0.87; p less than 0.001) and shortest atrial pacing cycle length associated with 1:1 conduction (r = 0.91; p less than 0.001). The AH interval during sinus rhythm (r = 0.74; p less than 0.001) and during atrial pacing at the shortest cycle length with 1:1 conduction (r = 0.52; p less than 0.001) had weaker correlations. Measures of concealed conduction did not improve the prediction of the mean or longest ventricular cycle length during atrial fibrillation. In conclusion, the refractory periods and conductivity of the AV node are the best indicators of the potential of the node to transmit atrial impulses to the ventricles during atrial fibrillation. The degree of concealed conduction in the AV node is a less important determinant of the mean ventricular rate during atrial fibrillation.

Atrial Fibrillation↗
PubMed1990

Magnitude and time course of beta-adrenergic antagonism during oral amiodarone therapy.

To examine the presence and time course of beta-adrenergic antagonism produced by amiodarone, the heart rate, QT interval and arrhythmia frequency in response to graded doses of isoproterenol were evaluated in eight patients treated with oral amiodarone for sustained ventricular tachycardia. Measurements were made before and every 2 days after beginning oral amiodarone therapy (600 mg twice daily). Isoproterenol was given in doses of 12.5, 25 and 50 ng/kg body weight per min. The mean heart rate at rest decreased from 73.1 +/- 17.8 beats/min on day 0 to 57.8 +/- 15.0 beats/min after 12 days of amiodarone therapy. A significant linear decline in heart rate at rest was observed until day 6 (p less than 0.05 for all comparisons). On all days isoproterenol produced a progressive increase in heart rate that reached 115.5 +/- 20.2 beats/min on day 0 and 94.2 +/- 18.5 beats/min on day 12. Amiodarone blunted the heart rate increase produced by isoproterenol on days 2 to 12 (p less than 0.05 versus day 0). This effect was present by day 2 and did not change significantly thereafter. The mean corrected QT (QTc) interval increased from 430 +/- 30 ms on day 0 to 449 +/- 63 ms on day 12. A significant linear increase in QTc interval was observed until day 6 (p less than 0.05 for all comparisons). There was no systematic effect of isoproterenol on the QTc interval. Five of eight patients had a significant number of isoproterenol-induced premature ventricular complexes. Ventricular ectopic activity in response to isoproterenol was abolished after 4 days of amiodarone therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1990

Effect of the intertrain pause on the ventricular effective refractory period measured by the extrastimulus technique.

This study determined the effect of the duration of the intertrain pause on the ventricular effective refractory period (VERP) measured by the extrastimulus technique using conventional eight-beat basic drive trains. In 50 subjects, the VERP was measured using a basic drive train cycle length of 500 msec, 2-msec steps in the extrastimulus coupling interval, and intertrain pauses of 0, 1, 4, 8, 20, 40, 60, or 180 seconds. The VERP increased significantly with each stepwise increment in the intertrain pause up to 20 seconds, then reached a plateau. The VERP measured with an intertrain pause of 20 seconds was a mean of 13 msec longer than when measured with a conventional 4-second pause. The results of this study demonstrate a direct relationship between the VERP and the duration of the pause separating the eight-beat basic drive trains used to measure the VERP. When the cycle length of the basic drive train is 500 msec, the VERP lengthens as the duration of the intertrain pause increases from 1 to 20 seconds, demonstrating that the basic drive trains exert a cumulative effect on the VERP when the intertrain pause is shorter than 20 seconds. A cumulative effect of the basic drive trains on the VERP is lost when the intertrain pause is 20 seconds or more.

Action Potentials↗
PubMed1990

The ventricular excitability-interval relationship in early diastole in humans: the influence of the electrode configuration during bipolar stimulation.

The purpose of this study was to determine the relationship between ventricular excitability and the extrastimulus (S2) coupling interval in early diastole in humans. The influence of the electrode configuration during bipolar stimulation was examined. Ventricular strength-interval curves were constructed using an eight beat drive train at a cycle length of 600 msec, 2-msec decrements in the S2 coupling interval, and 0.2-mA increments in the current intensity of S2 at each coupling interval. A transient dip in the excitation threshold was observed in early diastole during bipolar pacing when the distal electrode was the anode in six of 17 patients (35%). In contrast, this type of dip was not observed when the distal electrode was the cathode. The excitation threshold at the trough of the dip ranged from 1.0 to 2.2 mA. Unipolar strength-interval curves indicated that a dip occurred with anodal but not cathodal pacing. We postulated that the dip might interfere with the accurate determination of the ventricular effective refractory period by resulting in transient loss of ventricular capture during decremental scanning of diastole with S2. A gap in ventricular capture was produced in all six patients who demonstrated a dip in the bipolar strength-interval curve by selecting an S2 current intensity that fell within the dip. In conclusion, the bipolar strength-interval curve may display an early diastolic dip in the excitation threshold, depending on the electrode configuration.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1990

The effect of rate on prolongation of ventricular refractoriness by quinidine in humans.

In this study, the rate dependent effect of quinidine on the ventricular effective refractory period (VERP) was evaluated in 30 patients undergoing electropharmacological testing with quinidine. The VERPs were measured in the baseline state and after at least 2 days of treatment with 1,458-2,044 mg/day of quinidine gluconate (mean plasma quinidine concentration 2.2 +/- 0.7 mcg/mL). In 20 patients, the VERP was measured using conventional basic drive trains of 8 beats and basic drive cycle lengths of 600, 500, 400, and 350 msec. In another 10 patients, the VERP was measured after 3 minutes of continuous ventricular pacing at cycle lengths of 600 and 400 msec, and compared to the VERPs measured at the same basic drive cycle lengths using basic drive train durations of 2 and 8 beats. In the baseline state and after treatment with quinidine, the VERP shortened progressively as the basic drive train cycle length decreased and as the drive train duration increased to 3 minutes (P less than 0.001). Quinidine consistently prolonged the VERP by 9%-11% (P less than 0.001), regardless of the basic drive train cycle length. Quinidine's effect was also not affected by the basic drive train duration. In conclusion, the effect of quinidine on VERP in humans is independent of the rate of the basic drive train, both when measured using conventional 8-beat basic drive trains and when a three minute drive train duration is used in order to attain the maximum effect of the basic drive train cycle length on the VERP.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1990

Effect of atrioventricular relationship on ventricular refractoriness in humans.

Right ventricular refractory periods obtained using atrial and ventricular pacing with an atrioventricular (AV) interval of 160 ms were compared with those obtained with an AV interval of 0 ms in a group of 53 patients. The mean right ventricular effective refractory periods were longer at an AV interval of 160 ms than at an AV interval of 0 ms at pacing cycle lengths of 600 (mean 2.5 +/- 1.8 ms difference) and 400 ms (mean 3.8 +/- 2.4 ms difference; P less than 0.01). In a subset of 10 patients, left ventricular volumes measured by two-dimensional echocardiography demonstrated that pacing with an AV interval of 160 ms was associated with a higher end-diastolic volume and stroke volume than pacing with an AV interval of 0 ms (P less than 0.001). Autonomic blockade did not alter the relationship between AV interval and ventricular refractoriness. We conclude that 1) right ventricular refractory periods are shorter at an AV interval of 0 ms than at an AV interval of 160 ms; 2) these differences are not caused by changes in autonomic tone but are associated with differences in ventricular volumes; and 3) if precise determinations of ventricular refractoriness are desired, then the timing of atrial systole should be controlled by atrial pacing.

Aged↗
PubMed1990

Effects of resting vagal tone on accessory atrioventricular connections.

The purpose of this study was to determine the effects of resting vagal tone on accessory atrioventricular (AV) connections. Atropine (0.04 mg/kg) was administered to 13 patients with the Wolff-Parkinson-White syndrome and was found to have the following effects on the accessory AV connection: the anterograde block cycle length shortened from 305 +/- 51 to 279 +/- 54 msec (mean +/- SD; p less than 0.001); the retrograde block cycle length shortened from 288 +/- 57 to 251 +/- 50 msec (p less than 0.001); and the effective refractory period measured at a basic drive cycle length of 400 msec shortened from 295 +/- 45 to 265 +/- 47 msec in the anterograde direction (p less than 0.001) and from 283 +/- 18 to 261 +/- 12 msec in the retrograde direction (p less than 0.01). During atrial fibrillation, the mean ventricular cycle length decreased from 434 +/- 88 to 352 +/- 56 msec (p less than 0.001), and the shortest preexcited RR interval decreased from 302 +/- 56 to 256 +/- 43 msec (p less than 0.01). In another seven patients, propranolol (0.2 mg/kg) was administered before atropine, and atropine lengthened the anterograde block cycle length and the effective refractory period of the accessory AV connection; the magnitude of these effects was similar to that in the patients who did not receive propranolol. In conclusion, these data demonstrate that resting vagal tone exerts a direct depressant effect on accessory AV connections that does not require background sympathetic activity to be manifest.

Adult↗
PubMed1990

Long-term results of catheter ablation of idiopathic right ventricular tachycardia.

Ten consecutive patients with recurrent episodes of symptomatic, idiopathic, sustained monomorphic ventricular tachycardia (VT) originating in the right ventricle underwent an attempt at catheter ablation of the ventricular tachycardia. There were seven women and three men, with a mean age of 39 +/- 14 years (+/- SD). None of the patients had any evidence of structural heart disease. The VT had a left bundle branch block configuration and an inferior axis in each patient, and the mean cycle length was 313 +/- 75 msec. Based on the methods of induction of the VT and the response of the VT to verapamil, the VT mechanism was presumed to be reentry in six patients, triggered activity in three patients, and catecholamine-sensitive automaticity in one patient. Sites for ablation were guided by pace mapping, and an appropriate target site was identified in the right ventricular outflow tract in each patient. From one to three shocks of 100-360 J (mean total, 336 +/- 195 J) were delivered from a defibrillator between the tip of the ablation catheter (cathode) and a patch electrode on the anterior chest (anode). An electrophysiology test 7-9 days after ablation demonstrated that VT was still inducible in only one patient, who was treated with amiodarone. One other patient had a recurrence of VT 3 weeks after ablation and was treated with verapamil. Eight of 10 patients were not treated with antiarrhythmic medications and have had no episodes of symptomatic VT during 15-68 months of follow-up (mean follow-up, 33 +/- 18 months). There were no acute or long-term complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗