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Biomedical subjects

A Hamer

Publications and source records attributed to A Hamer.

36 records · Page 2Linked to original sources
PubMed1983

Evaluation of amiodarone therapy in the treatment of drug-resistant cardiac arrhythmias: long-term follow-up.

The clinical efficacy of amiodarone in the management of complex cardiac arrhythmias refractory to therapy with two or more conventional or other investigational antiarrhythmic agents was determined by long-term follow-up in patients who had received the drug for at least 3 months. A total of 181 patients, classified into four groups (group 1, supraventricular arrhythmias, n = 42; group 2, frequent ventricular premature complexes, n = 46; group 3, nonsustained ventricular tachycardia, n = 16; and group 4, sustained ventricular tachycardia, n = 77) received a daily maintenance dose of 200 to 800 mg amiodarone for up to 30 months. There was a total of 26 deaths (14%). Ten of these were probably attributable to arrhythmia, although all patients had either good or excellent response to therapy over a mean follow-up of 14.9 months prior to death. The drug had to be permanently discontinued because of side effects in only three patients, and in the majority of patients with side effects, symptoms could be alleviated with adjustment of dosage, thyroid replacement therapy, or temporary cessation of therapy. We conclude that amiodarone is highly effective in high-risk patients with complex refractory cardiac arrhythmias, and that close monitoring and prompt recognition of side effects and appropriate adjustment of dosage or institution of supplemental or replacement therapy (in less than 5% of patients) will allow continuation of amiodarone. The benefit of suppression of symptomatic arrhythmias and the potential of prevention of sudden death clearly outweigh the modest incidence of severe side effects.

Aged↗
PubMed1983

Electrophysiologic studies in survivors of late cardiac arrest after myocardial infarction.

Nine patients resuscitated from life-threatening ventricular arrhythmias (VA) within 3 months of an acute myocardial infarction (AMI) underwent electrophysiologic studies (EPS) with clinical follow-up for at least 12 months. Neither reinfarction, drug therapy, nor electrolyte imbalance was a precipitating factor. VA was induced by ventricular pacing in six of nine patients. Five patients were prescribed empiric drug therapy, while the four other patients had repeated EPS to select optimal drug therapy. One patient remained unstable and died of VA in the hospital. No patient was discharged and successfully maintained on a drug known to prevent induction of VA, yet only two patients (25%) had a further recurrence of VA, one fatal. Our findings suggested that either drug therapy that is determined empirically or found not to suppress the induction of VA during EPS can be associated with a successful outcome in some of these patients, or the natural history of VA after myocardial infarction is that they are self-limiting in the absence of a new ischemic event.

Arrhythmias, Cardiac↗
PubMed1983

Atrioventricular node reentry: intravenous verapamil as a method of defining multiple electrophysiologic types.

Fourteen patients with recurrent supraventricular tachycardia (SVT) underwent electrophysiological evaluation. Each patient was shown to have reentry confined to the region of the atrioventricular (AV) node. Verapamil, 0.075 to 0.15 mg/kg was administered intravenously to each patient during a stable episode of SVT, resulting in termination in each instance. There was more than one mechanism for termination of SVT. Nine patients showed termination by anterograde AV node block preceded by an increase in conduction time in the anterograde limb of the tachycardia circuit (Ae-H intervals) with no change in the conduction time in the retrograde limb (H-Ae intervals). Three patients showed termination by block in the retrograde limb of the circuit preceded by increases in both Ae-H and H-Ae intervals. An additional example of termination by spontaneous ventricular premature complexes and usurpation by sinus rhythm were also seen. Common features were that verapamil had significant effects on anterograde and retrograde conduction and refractoriness in the AV node. It prolonged the refractory periods of both fast and slow pathways in patients with dual anterograde AV node pathways, and observable effects on retrograde conduction and refractoriness were seen even in patients with constant ventriculoatrial conduction times during incremental ventricular pacing in a control study. However, three distinct groups of patients were identified on the basis of their response to ventricular pacing in a control study and upon verapamil effects recorded during their SVT. An explanation for these latter findings may be that there is a normal variation in the retrograde response of parts of the AV node to ventricular pacing, and a variability in some of the patients' responses to verapamil.

Adult↗
PubMed1983

Transient hemodynamic dysfunction after myocardial revascularization. Temperature dependence.

We studied hemodynamics and the effects of right atrial pacing (110 beats/min) following complete myocardial revascularization and hypothermic multidose potassium crystalloid cardioplegia in 12 patients with a normal preoperative left ventricular ejection fraction (LVEF). Measurements were made immediately preoperatively, postoperatively at specified temperatures during the rewarming period (90 degrees F, 94 degrees F, and 98 degrees F), and at 24 hours. No patient had a perioperative myocardial infarction. At 90 degrees F, hemodynamics were characterized by significant decreases in cardiac index, stroke volume index, and left ventricular stroke work index (LVSW) and an increase in systemic vascular resistance index (SVRI) compared to preoperative values (p less than 0.05). Right atrial pacing significantly increased cardiac index preoperatively and 24 hours postoperatively, but not during the rewarming period. Over the entire rewarming period (90 degrees F to 98 degrees F), each of the following variables correlated with temperature: cardiac index (r = 0.71 in sinus rhythm and r = 0.66 with right atrial pacing); stroke volume index (r = 0.33 and 0.66); SVRI (r = -0.80 and -0.64); LVSW (r = 0.37 and 0.73); and heart rate in sinus rhythm (r = 0.51). During the rewarming period, there was an inverse relationship between cardiac index and SVRI (r = -0.87). In conclusion, after myocardial revascularization: (1) transient hemodynamic dysfunction occurs during the rewarming period (90 degrees F to 98 degrees F); (2) this dysfunction is temperature-dependent; and (3) right atrial pacing at 110 beats/min does not improve hemodynamic function during the rewarming period. Temperature must be considered in the evaluation of left ventricular and hemodynamic function following myocardial revascularization.

Adult↗
PubMed1982

Electrophysiologic effects of chronic amiodarone therapy in patients with ventricular arrhythmias.

Detailed electrophysiologic studies were performed in nine patients with chronic refractory ventricular arrhythmias before and after 7 to 20 weeks (mean 11 weeks) of amiodarone therapy. The amiodarone dose at the time of the repeat study ranged from 400 to 800 mg/day. The drug reduced the sinus rate (p less than 0.001) and prolonged the sinoatrial conduction time (p less than 0.05) with some prolongation of the corrected sinus node recovery time. Intra-atrial conduction was slightly prolonged both in sinus rhythm and during atrial pacing. Anterograde conduction through the AV node was significantly prolonged both in sinus rhythm (p = 0.001) and during atrial pacing (p less than 0.005), and Wenckebach AV block was seen at significantly lower atrial pacing rates after the drug (p less than 0.005). The HV interval was prolonged both in sinus rhythm (p less than 0.05) and during atrial pacing (p = 0.001), and so was the QRS width during atrial pacing (p less than 0.005) and the QT interval in sinus rhythm (p less than 0.005) and during atrial pacing (p less than 0.005). Significant prolongation of the refractory periods in the atrium, AV node, and ventricular muscle were also seen following the drug. We concluded that the significant electrophysiologic effects of this drug throughout the heart during chronic oral use attest to its clinical effectiveness in patients with atrial and ventricular arrhythmias. With due care and despite its effects on the HV interval and QRS width, it can be used in patients with intraventricular conduction defects complicating severe organic heart disease.

Aged↗
PubMed1982

Prediction of sudden death by electrophysiologic studies in high risk patients surviving acute myocardial infarction.

Seventy patients surviving a myocardial infarction complicated by heart failure or arrhythmias, or both, were studied 7 to 20 days after the infarction. Twenty-four hour electrocardiographic ambulatory monitoring and intracardiac electrophysiologic studies were performed in each patient. Electrophysiologic studies included introduction of single right ventricular premature stimuli during sinus rhythm (70 patients), atrial pacing (35 patients) and ventricular pacing (70 patients) at a stimulating voltage of 2 V, with the use of higher stimulating voltages (up to 10 V), and double right ventricular premature stimuli in 33 patients and pacing at a second right ventricular site in 50 patients. A repetitive response was defined as two or more spontaneous ventricular depolarizations in response to the premature stimuli, with His bundle reentry and aberrant conduction of supraventricular impulses excluded by a His bundle recording. Repetitive responses were initiated in 20 patients, and 12 patients had responses that were either sustained ventricular tachycardia or self-terminating ventricular tachycardia of more than five complexes in duration. The finding of a repetitive response was not related to the occurrence of complex ventricular arrhythmias during ambulatory monitoring or in the coronary care unit. Five of the 12 patients with sustained or self-terminating responses of more than five complexes died during the 12 month follow-up period, 4 suddenly, and these responses were significantly associated with late sudden death (p less than 0.05), because only 1 of 25 patients with responses of fewer than five complexes or no response to maximal provocation died suddenly. It is concluded that induced responses of more than five complexes in duration may be an important indicator of a potentially reversible risk of sudden death after myocardial infarction.

Adult↗
PubMed1982

The potentiation of warfarin anticoagulation by amiodarone.

The potentiation of the anticoagulant effect of sodium warfarin by amiodarone is reported in 10 patients. Amiodarone appears to augment the depression of vitamin K-dependent coagulation factors caused by warfarin by an uncertain mechanism, and may lead to serious bleeding. The maintenance dose of warfarin should be halved when amiodarone and warfarin are prescribed together.

Aged↗
PubMed1981

Use of lignocaine and atropine autoinjectors for patients at high risk of sudden death and reinfarction after myocardial infarction.

Twenty-five patients entered a prospective study to assess the usefulness of atropine and lignocaine autoinjectors for coronary events after discharge from hospital after a definite, complicated myocardial infarction. They were selected on the basis of being at high risk of sudden death and reinfarction, being less than 70 years of age and being able to maintain a close liaison with the hospital. One or both autoinjectors were used for five reported events (four of collapse, one of chest pain) in four patients, with possible benefit in two instances. Six patients collapsed and died, despite the use of autoinjectors in three of their fatal collapses. In our experience, the use of autoinjectors has been of little observable benefit, perhaps due to the lack of specific warning symptoms preceding the onset of lethal arrhythmias, so that the injectors were often used for unobserved collapses when the chances of survival were remote.

Aged↗
PubMed1981

Effects of verapamil on supraventricular tachycardia in patients with overt and concealed Wolff-Parkinson-White syndrome.

Verapamil (0.15 mg/kg) intravenously, was administered to 19 patients with recurrent supraventricular tachycardia (SVT) undergoing electrophysiological evaluation. Twelve patients had overt Wolff-Parkinson-White (WPW) syndrome and seven patients had concealed accessory pathways conducting in the retrograde direction only. Verapamil had a significant effect in delaying conduction and prolonging refractoriness in the atrioventricular (AV) node, but no significant actions on any of the other cardiac tissues that formed the tachycardia circuit in these patients. In particular, it had no significant effects on anterograde or retrograde bypass conduction or refractoriness. Sustained SVT was initiated in 15 patients, and was terminated within 60 to 105 seconds of a 30-second injection of verapamil in 13 patients. Cycle length alternation during SVT was seen in six patients prior to reversion, and spontaneous ventricular complexes (VPCs) were observed following verapamil administration in five patients. Two patients with apparently normal sinus node function showed prolongation of their sinus node recovery times immediately following reversion of SVT by verapamil. Echo zones were assessed before and after verapamil, and sustained or self-terminating SVT could still be induced after the drug in 13 of the 15 patients who had sustained SVT beforehand. It was concluded that intravenous verapamil was effective in terminating sustained SVT in the majority of patients with overt or concealed WPW and that, despite a potential for sinus node depression and the initiation of VPCs, it had no clinically significant side effects. The ability to reinitiate SVT following its administration suggests the need for immediate follow-up with maintenance drug therapy.

Adult↗
PubMed1981

Patient initiated implantable pacemakers for paroxysmal supraventricular tachycardia.

Seven patients with recurrent paroxysmal supraventricular tachycardia (PSVT) resistant to standard drug therapy were treated with patient initiated implantable pacemakers. All patients had required frequent hospital admissions and cardioversions prior to pacemaker implantation. Two patients had Wolff-Parkinson-White (WPW) syndrome on their surface ECGs and five patients had no ECG evidence of preexcitation. All patients had detailed electrophysiological studies. Three patients had junctional tachycardia, one patients had reciprocating atrial tachycardia and in three, including one with normal surface ECG, retrogradely conducting accessory atrio-ventricular connections (AAVC) formed a part of the tachycardia circuit. Initiation and termination of tachycardia were re-checked at subsequent studies. On the basis of these studies, two patients with WPW syndrome had right ventricular endocardial leads and custom-built, magnet actuated pacemakers capable of delivering right ventricular coupled stimuli at fixed, present intervals of 200 and 400 ms. Both these pacemakers provided inconsistent reversions and proved unsatisfactory. In the remaining five patients, a unipolar tined J-shaped right atrial (RA) lead (Medtronic 6991) and a radiofrequency (RF) receiver (Medtronic 5998T) were implanted and enabled patients to overdrive ranged from 14 to 20 months. Several episodes of PSVT have been consistently reverted and none have required hospitalisation or cardio-version. Two patients had transient atrial fibrillation following the application of RF pacemaker. Three have required no antiarrhythmic drugs and in two the drug therapy has been greatly reduced and simplified. The Medtronic 6991 lead provided satisfactory RA stimulation without dislodgement. In carefully selected patients with PSVT, RF pacemakers provide a useful mode of treatment.

Adult↗
PubMed1979

Effect of mianserin on cardiac conduction.

A cardiovascular study of a new antidepressant, mianserin, given at 60 mg a day for a three-week period to 10 ambulant, moderately depressed patients is described. No effects on cardiac conduction were found by means of His bundle electrocardiography. Nine of 10 depressed patients improved while on the medication; mild sedation was the only side effect noted.

Adult↗
PubMed1979

Predictors of reinfarction and sudden death in a high-risk group of acute myocardial infarction survivors.

75 patients aged under 70 years who had survived acute myocardial infarction complicated by both significant arrhythmias and cardiac failure were followed-up for 1 year in an attempt to identify features which suggest the likelihood of late death or reinfarction. Patients were carefully instructed in the identification and importance of possible prodromal symptoms and the availability of a mobile intensivecare ambulance service and a 24 h hospital control centre. Horizontal ST-segment depression or anginal pain on an exercise test done within 6 weeks of infarction was a useful predictor of late death. Routine twice weekly E.C.G. recordings taken by telephone transmitter at rest and after mild exertion resulted in the identification of significant arrhythmias in only 7 patients. 13 patients (17%) died, 5 of them instantaneously. 4 of the 13 patients and 22 of the 62 survivors reported "prodromal symptoms". Unreported prodromal symptoms were elicited retrospectively in 14 of the 62 survivors and from the relatives of 4 of the 13 patients who died. Thus, 35% of prodromal symptoms were not reported despite intensive patient education and counselling. The incidence of "prodromal symptoms" was no higher in patients who died than in those who did not die.

Acute Disease↗
PubMed1978

Absence of formation of cerebrospinal fluid in the spinal subarachnoid space of the cat.

It is widely believed that formation of cerebrospinal fluid (CSF) takes place within the cerebral ventricles--80 to 85% being produced by the choroid plexus and the remaining 15 to 20% being secreted by the lining ependyma. It has also been suggested that CSF is formed within the subarachnoid space. To investigate this possibility. CSF formation was measured in the isolated subarachnoid space of the cat. In 16 animals that underwent 26 steady-state perfusions, the rate of formation of CSF was found to be only 0.00005 +/- 0.00056 (SE) ml/min. It is therefore concluded that little or no CSF is formed in the spinal subarachnoid space of the cat.

Animals↗