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N D Berman

Publications and source records attributed to N D Berman.

At least 19 recordsLinked to original sources
PubMed1990

The cellular electropharmacology of mexiletine combined with sotalol in porcine papillary muscle and Purkinje fibre. I. Alteration of mexiletine-induced Vmax depression.

Using standard microelectrode techniques, the authors compared the effects of 15 to 125 microM concentrations of mexiletine, 31 to 500 microM concentrations of sotalol and 15 to 125 microM of mexiletine combined with 125 microM sotalol, on the beat-to-beat maximum rate of depolarization of phase 0 of the action potential (Vmax) of porcine papillary muscles and Purkinje fibres stimulated by 30 beat trains at a frequency of 1 Hz. Sotalol alone had no effect on Vmax. Mexiletine caused both tonic and use-dependent depression of Vmax in papillary muscle. In the presence of sotalol, tonic Vmax depression was exaggerated, while use-dependent depression was attenuated. In Purkinje fibres, mexiletine exposure resulted in tonic Vmax depression, but no use-dependence could be demonstrated at this frequency. These results are best explained in the context of the modulated receptor hypothesis with the added consideration of two receptors--one within and one external to the sodium channel.

Action Potentials↗
PubMed1990

The cellular electropharmacology of mexiletine combined with sotalol in porcine papillary muscle and Purkinje fibre. II. Effects on action potential duration and refractoriness.

Using standard microelectrode techniques, the authors compared the effects of 15 to 125 microM concentrations of mexiletine, 31 to 500 microM concentrations of sotalol and 15 to 125 microM of mexiletine combined with 125 microM sotalol, on the beat-to-beat action potential duration and refractoriness of porcine papillary muscles and Purkinje fibres stimulated by 30 beat trains at a frequency of 1 Hz. Sotalol alone prolonged action potential duration and effective refractory period without altering their ratio. Mexiletine shortened action potential duration while prolonging refractoriness. When the two drugs were combined, action potential duration was shortened to the same extent as with mexiletine alone, but refractoriness, particularly in papillary muscle, was further prolonged. These changes suggest additive inhibition of the sodium window current by both drugs. Purkinje action potential duration was longest in the first beat of the train, while in papillary muscle, this beat was shortest. Exposure to either or both drugs eliminated the prolongation of duration of the first beat of the train in Purkinje fibre. Thus, the phenomenon of restitution, which prolongs the duration of the first beat after a long diastolic interval, appears also to be related to the sodium window current.

Action Potentials↗
PubMed1988

A comparison of the cellular electrophysiology of mexiletine and sotalol, singly and combined, in canine Purkinje fibers.

To determine if combinations of mexiletine and sotalol retain Class I and III electrophysiologic actions, using standard microelectrode techniques, we examined the electrophysiologic effects on canine Purkinje fibers of solutions of mexiletine (3.1-100 microM), sotalol (3.1-400 microM), and combinations of the two drugs, at stimulation frequencies of 1.5 and 2.0 Hz. The combinations consisted of 12.5 microM of one drug combined with 3.1, 12.5, and 50 microM of the other. Mexiletine caused a concentration dependent depression of Vmax, the degree of depression always being greater at the more rapid frequency. At concentrations above 50 microM, sotalol depressed Vmax slightly. Increasing the stimulation frequency did not result in further Vmax depression. The addition of sotalol did not alter the Vmax depression produced by mexiletine but prior exposure to sotalol attenuated the effect of subsequent mexiletine. Both drugs reduced action potential amplitude and in combination their effects on this parameter were additive. Sotalol prolonged and mexiletine shortened action potential duration. Low concentrations of mexiletine reversed the prolongation caused by sotalol, whereas the addition of sotalol did not alter the effect of mexiletine. Mexiletine shortened the effective refractory period at low concentrations and prolonged it at high concentrations. Sotalol prolonged the effective refractory period at all concentrations. Exposure to a low concentration of sotalol did not alter the effects on the effective refractory period of subsequent exposure to mexiletine but a low concentration of mexiletine reduced the prolongation from subsequent sotalol. Thus, the combination of mexiletine and sotalol may add a Class II action to the Class I effects of mexiletine but the mexiletine prevents the Class III effects of sotalol.

Action Potentials↗
PubMed1987

The cellular electropharmacology of the simultaneous administration of propranolol and mexiletine: a class I and II antiarrhythmic drug combination.

The addition of propranolol to mexiletine may reduce the adverse effects of mexiletine and possibly increase its efficacy. We compared the cellular electrophysiologic effects of this combination with mexiletine and propranolol alone, over concentration ranges of 3.2 to 100 microM mexiletine and 0.80 to 25.0 microM propranolol, using standard microelectrode techniques and a stimulation frequency of 1.5 Hz. Mexiletine and propranolol both depressed the rate of rise of phase 0 (Vmax) with concentration-response curves of similar slope and a relative potency of 8:1, propranolol to mexiletine. Thus, combinations of 8:1 molar ratios of mexiletine to propranolol were assessed. The combination depressed Vmax to the same extent as mexiletine or propranolol alone. Mexiletine, propranolol and the combination all shortened action potential duration (APD) to the same extent. At low concentration mexiletine, propranolol and the combination shortened effective refractory period (ERP). At 25 microM mexiletine, this effect reversed and ERP began lengthening. The effect of the combination paralleled mexiletine while with propranolol alone the reversal did not occur until the highest concentration was reached. Mexiletine prolonged ERP relative to APD, an effect not shared by propranolol and attenuated with the combination (P less than 0.05). We conclude that combining propranolol with mexiletine does not alter any of the cellular electrophysiologic effects of mexiletine except the prolongation of ERP relative to APD. Although this may be an important antiarrhythmic effect, the extent by which in vivo concentrations of propranolol may reduce the clinical antiarrhythmic efficacy of mexiletine is likely to be negligible.

Action Potentials↗
PubMed1987

Persistence of the electrophysiologic effects of mexiletine in canine Purkinje fibers alters the response to subsequent hypoxia.

The persistence of cellular electropharmacologic effects of mexiletine on canine Purkinje fibers was studied utilizing standard microelectrode techniques and two different protocols. In the first, the tissue was exposed to hypoxic perfusion before and 30 min after perfusion with one of the following: mexiletine hydrochloride 6.25 microM solution, mexiletine hydrochloride 12.5 microM solution, or drug-free Tyrode's solution. With the higher concentration of mexiletine, depression of the maximal upstroke velocity (Vmax) persisted 30 min after drug washout and subsequent exposure to hypoxia did not result in the anticipated shortening of action potential duration but did prevent the restoration of normal Vmax. After perfusion with the lower concentration of mexiletine, Vmax was not depressed and hypoxic action potential duration shortening was not prevented. In the second protocol, Purkinje fibers were perfused with 12.5 microM mexiletine hydrochloride solution and then exposed to hypoxia after 15, 30, 45, or 60 min of perfusion with drug-free solution. Depression of maximal upstroke velocity and shortening of action potential duration persisted during washout, returning to control values by 45 min, although mexiletine was not detectable in the tissue bath after 10 min of washout. Hypoxia initiated at 15 or 30 min of washout failed to produce the anticipated shortening of action potential duration. At 45 and 60 min, action potential duration was shortened by hypoxia. We concluded that mexiletine depression of Vmax and shortening of action potential duration may persist in the absence of drug. Further shortening of action potential duration in response to hypoxia is prevented during this period. The persistence of Vmax depression is prolonged by hypoxia.

Action Potentials↗
PubMed1987

Apparent pacemaker malfunction due to ventricular blanking.

Electrocardiographic interpretation in patients with dual chamber pacemakers requires an intimate understanding of their manner of functioning. This report describes a patient whose pacemaker was suspected of malfunction because of failure to sense premature beats. This sense-failure resulted from the fortuitous concurrence of the sensed portion of the premature beat with the ventricular blanking period and was resolved by reducing the low rate limit of the pacemaker. Three principles must be recognized in interpreting suspected failure of sensing: 1. The channel of origin of the pacing artifact must be identified. 2. The surface QRS morphology does not necessarily correspond to the signal detected by the pacemaker. 3. Failure to sense does not necessarily equal pacemaker malfunction.

Cardiac Complexes, Premature↗
PubMed1986

Antiarrhythmic therapy in the elderly: pacemakers and drugs.

Investigations of syncope often fail to demonstrate any abnormality. However, in view of the ease of permanent pacemaker implantation and the potential dangers of recurrent syncope, patients with this symptom should receive pacemaker therapy. In general, acute therapy of any tachyarrhythmia associated with hemodynamic collapse consists of DC cardioversion, but skillful use of drug therapy and, occasionally, pacemaking are also highly important in preventing recurrences.

Aged↗
PubMed1986

Comparative electropharmacology of mexiletine, lidocaine and quinidine in a canine Purkinje fiber model.

Although said to be lidocaine-like, there is evidence that mexiletine has some properties similar to those of quinidine. To evaluate the relationship between the effects of these three drugs we analyzed their effects on action potentials of Purkinje fibers from canine false tendons. Experiments with each drug were done on single preparations from each of six dogs over the concentration range 0.31 to 10.0 X 10(-5) M. Lidocaine shortened action potential duration and effective refractory period with a log concentration-response relationship. The maximum velocity of phase "0" (Vmax) was unaffected at low concentrations and only slightly depressed at high concentrations. Quinidine also shortened action potential duration and effective refractory period but the effect levelled off at midrange and was reversed at higher concentrations. Quinidine depressed Vmax throughout the concentration range studied. Mexiletine shortened action potential duration with a log concentration response relationship. Effective refractory period was shortened at low concentrations but the effect levelled off and then reversed at higher concentrations of the drug. Mexiletine had no effect on Vmax at the lower end of the concentration curve but did suppress this parameter at higher concentrations. Mexiletine resembled lidocaine in its effect on Vmax and action potential duration whereas the effects of quinidine on these two parameters were distinct. On the other hand, the effects of mexiletine on effective refractory period were more akin to quinidine than lidocaine.

Action Potentials↗
PubMed1979

Patient-initiated transtelephone transmission of electrocardiographic signals in the diagnosis of arrhythmias.

Thirty-one patients who had complained of recurrent palpitations were given transtelephone transmitters of electrocardiographic signals and instructed to use the transmitters while they were having symptoms. From the transcribed electrocardiograms sinus tachycardia was documented in 12 patients, paroxysmal atrial tachycardia in 7, atrial fibrillation in 4, atrial flutter in 3, frequent ventricular premature beats in 4 and ventricular tachycardia in 1. Patient-initiated transtelephone transmission of electrocardiographic signals was found to be an effective means of documenting the nature of symptomatic paroxysmal tachycardia.

Adolescent↗
PubMed1979

The elderly patient in the coronary care unit. II. Incidence and treatment of arrhythmias.

In 1976, 130 patients aged 70 or older were admitted to the Coronary Care Unit (CCU) at Toronto Western Hospital. Arrhythmias were noted in all but 24 percent. Digoxin was given to 53 patients, lidocaine to 24, propranolol to 28, and quinidine to 11. In 2 patients, cardioversion by direct current was required for supraventricular arrhythmias. In 26 patients, temporary pacemakers were used. Of 13 patients who experienced at least one cardiac arrest in the CCU, 10 survived to be discharged to the ward. In total, only 12 of the 130 elderly patients died in the hospital, and in only 3 of these was arrhythmia the primary cause of death. The treatment of arrhythmias in the elderly is as successful and rewarding as in younger patients. Indications for the various antiarrhythmic drugs are similar. Except for digoxin, the dosages of such drugs for the elderly are the same as those for younger patients. Adverse effects apparently are not more common in the elderly.

Aged↗
PubMed1979

The elderly patient in the coronary care unit. I. Acute myocardial infarction.

In a Coronary Care Unit (CCU) with no age barrier for admission, 21 percent of the patients admitted in 1976 were aged 70 or older. Myocardial infarction was documented in 55 of 130 elderly patients. The overall incidence of arrhythmias was similar to that for younger patients. The mean duration of stay in the unit and the CCU mortality (9.1 percent) were similar in both elderly and younger patients, as was the in-hospital mortality rate. Of the patients who survived hospitalization, 75.6 percent were still living 18.1 months after the myocardial infarction. The elderly patient is as likely as the younger one to benefit from admission to a CCU.

Acute Disease↗
PubMed1979

Pneumopericardium following laparoscopy.

There have been no published reports of pneumopericardium complicating laparoscopy. Following an apparently uncomplicated laparoscopy, a 35-year-old woman developed pneumopericardium associated with subcutaneous emphysema of the neck. This resolved without specific therapy and without sequelae.

Adult↗
PubMed1978

Influence of aortocoronary bypass surgery on employment.

Aortocoronary bypass operations are expensive. Economic benefit might be derived if such operations influenced the ability of persons with symptomatic coronary artery disease to be employed. Follow-up data were obtained for 329 survivors of bypass operations 2 to 60 months (mean, 22.9 months) postoperatively; 178 had been working prior to the operation and 213 were working at the time of follow-up, for a net gain of 35 employed patients. Therefore, bypass surgery does lead to a small but significant increase in the proportion of angina patients who are employed.

Adult↗
PubMed1978

The surface electrocardiogram in complete intra-his heart block.

In some cases, the surface ECG may be useful in predicting that the level of heart block is intra-His rather than supra-His. In five patients with third degree heart block the level of block was documented to be within the His bundle. In all five, the surface ECG showed an escape rhythm with QRS complexes of less than 0.10s. duration. The initial QRS forces were abnormal in that "septal" q waves were not present in leads 1 and V6. Two of the five patients had occasional conducted beats with normal "septal" q waves. Thus, heart block associated with an escape rhythm of narrow QRS morphology but abnormal septal depolarization may indicate that the level of the block is intra-His rather than supra-His.

Aged↗
PubMed1978

Permanent pacing in the elderly.

A total of 89 patients, age 80 years or older at the time of initial permanent pacemaker implantation, were followed for 10 to 128 months [mean 32.7]. There were 54 males and 35 females. The mean age was 84.8 years. There were 51 patients age 80-84, 25 age 85-89, and 13 age 90-94. The actuarial 5-year survival was 45%. Complications occurred in 23 patients [40 episodes]. To date, 41 patients have already required at least one pulse generator replacement and 2 patients have already required 5 replacements. All but 3 patients were symptomatic prior to pacing and 56 were asymptomatic at last follow-up. Permanent pacing in the elderly is therapeutically rewarding and not associated with excess morbidity.

Actuarial Analysis↗
PubMed1977

Myocardial infarction, hyperthyroidism and normal coronary arteries: report of two cases.

Myocardial infarction is uncommon in persons with hyperthyroidism and also uncommon in the absence of demonstrable coronary artery disease. Cardiac catheterization and selective coronary angiography were performed in two men following apparent myocardial infarctions. Both patients were 33 years of age, thyrotoxic and angiographically free of coronary artery abnormalities.

Adult↗