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Biomedical subjects

E Rowland

Publications and source records attributed to E Rowland.

At least 109 records · Page 6Linked to original sources
PubMed1985

Hemodynamic effects of nifedipine given alone and in combination with atenolol in patients with impaired left ventricular function.

The acute intravenous (IV) (0.1, 0.2 and 0.4 microgram/kg/min over 10 minutes each) and chronic oral (60 mg/day) administration of nifedipine was examined in 9 patients with significantly impaired left ventricular (LV) function (ejection fraction [EF] on radionuclide scanning was 0.20 to 0.40) who were already receiving beta-blocker therapy (greater than 25% reduction in peak exercise heart rate) with atenolol, 100 to 200 mg/day. The mean control LV end-diastolic pressure (EDP) at cardiac catheterization and EF for the group as a whole were 30 +/- 3 mm Hg (range 20 to 42) (mean +/- standard error of the mean) and 28.5 +/- 2.4%, respectively. Three of the 9 patients had hemodynamic deterioration and LV failure at some stage during the study, and their mean LVEDP and EF were 38 +/- 3 mm Hg (range 33 to 42) and 22.6 +/- 2.7%, respectively. In the 6 patients who tolerated the full treatment protocol, the mean LVEDP and EF were 26.5 +/- 2.0 mm Hg (range 20 to 35) and 31.5 +/- 2.8%, respectively. Seven patients received IV nifedipine, which had a negative inotropic action but did not precipitate cardiac decompensation. Chronic oral administration of nifedipine in combination with atenolol precipitated LV failure only in those with the lowest EF and highest LVEDP; usually LV failure was present with atenolol alone. Extensive infarction, frequently complicated by LV failure at the time, LVEDP greater than 32 mm Hg and control resting EF less than 30% were associated with LV failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1985

Local abnormalities of right ventricular depolarization after repair of tetralogy of Fallot: a basis for ventricular arrhythmia.

Ventricular arrhythmia is common after repair of tetralogy of Fallot (TF) and may cause sudden death. To explore the mechanisms, ambulatory electrocardiographic monitoring and electrophysiologic studies were undertaken, without the use of provocative tests, in 22 patients 5 to 24 years (mean 13) after repair. His-Purkinje and right ventricular (RV) apical activation times were measured to assess conduction. Endocardial mapping of the right ventricle was performed, with additional recordings from the left ventricle in 10 patients, to detect abnormalities of local depolarization and repolarization. Local RV electrograms were fractionated or delayed in 12 patients (55%) at 1 or more RV sites (septum in 7 patients, outflow in 7, free wall in 2 and apex 1 patient), reflecting disordered depolarization, but left ventricular recordings were normal in all. Ventricular arrhythmia out of hospital was more common (p less than 0.05) and more severe (p less than 0.01) in the patients with depolarization abnormalities than in those with normal electrographic findings. In contrast, there was no association between ventricular arrhythmia and conduction disturbances. Abnormalities of RV repolarization, consisting of low-frequency signals after the T wave, were observed in 17 patients (77%), but were not associated with arrhythmia. Thus, ventricular arrhythmia during daily life was associated with fractionated depolarization at multiple sites in the right ventricle. This suggests that there are widespread areas of RV myocardial damage that provide substrates for ventricular tachycardia.

Adolescent↗
PubMed1985

Intracardiac contrast echoes during transvenous His bundle ablation.

Two patients undergoing endocavitary ablation for resistant supraventricular tachycardia had cross sectional echocardiography performed during the ablative procedure. In both cases immediate opacification of the right heart cavities occurred at the time of the current discharge. The contrast effect was similar to that resulting from a peripheral venous injection of dextrose or saline during echocardiography for the diagnosis of intracardiac shunts. In one patient contrast echoes were also seen in the left ventricle. This contrast effect may be produced by gaseous release or blood element destruction. The risk of embolisation in patients undergoing endocavitary ablation, particularly on the left side of the heart, should be further evaluated.

Adult↗
PubMed1984

Amiodarone for long-term management of patients with hypertrophic cardiomyopathy.

Fifty-three patients with hypertrophic cardiomyopathy who had serious arrhythmias (45 patients), refractory chest pain (5 patients) or a high risk of sudden death (3 patients) received amiodarone for 6 to 96 months (median 18) after completion of a loading and an initial maintenance period. The dose of amiodarone was altered by 50 to 200 mg/day at 3- to 6-month intervals, guided by electrocardiographic monitoring, plasma drug level measurements and side-effect questionnaires. Ventricular tachycardia was suppressed in 24 patients (92%) with doses of 100 to 400 mg/day (median 300); none died suddenly during a mean follow-up of 27 months. Although symptomatic episodes of frequent or prolonged supraventricular tachycardia or paroxysmal atrial fibrillation/flutter were abolished in 8 of 9 patients on 100 to 600 mg/day (median 300), in 1 patient incessant atrial flutter developed that was relatively refractory to direct-current cardioversion. In 11 patients with atrial fibrillation, sinus rhythm was restored in 7 (after direct-current cardioversion in 3) with doses of 100 to 600 mg/day (median 300) and has been maintained in 5 with associated improvement in symptoms. Despite discontinuation of beta-blocker therapy, chest pain was unchanged in 17 patients, was impaired in 11 and was worse in only 2. Amiodarone was discontinued in 3 patients; in 1 because of hair loss, in 1 because of neurologic symptoms and in 1 because of facial discoloration; in the latter 2 patients, amiodarone was restarted after 1 and 14 months, and was tolerated and effective at the lower dosage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Ventricular tachycardia of left bundle branch block configuration in patients with isolated right ventricular dilatation. Clinical and electrophysiological features.

Electrophysiological studies showed ventricular tachycardia in five patients (four male, one female) with isolated right ventricular dilatation. All had been asymptomatic before the onset of palpitation which had developed in adolescence or early adult life. Tachycardia had been associated with syncope in four patients, and three had been resuscitated from ventricular fibrillation before investigation. The electrocardiogram during ventricular tachycardia showed a left bundle branch block pattern, and endocardial mapping at electrophysiological study confirmed the right ventricular origin. The presenting tachycardia could be induced in all patients by programmed stimulation, and in three patients ventricular tachycardia of differing configuration could be induced, but the right ventricular origin and left bundle branch block pattern were maintained. In two patients ventricular tachycardia degenerated into ventricular fibrillation. Cineangiography, cross sectional echocardiography, and multigated radionuclide angiography confirmed the dilated abnormal right ventricle while indicating that left ventricular function was normal. On resting electrocardiograms T wave inversion over the right precordial leads was the sole abnormality. There were no signs of right heart failure and exercise tolerance was normal. Four patients have received maintenance treatment with antiarrhythmic drugs, and one had undergone operative mapping and ablative surgery. Thus ventricular tachycardia complicating right ventricular dilatation may be associated with serious symptoms and ventricular electrical instability; and in adults it may be suspected on clinical grounds by inverted T waves in the right precordial leads.

Adult↗
PubMed1984

Assessment of a prototype implantable cardioverter for ventricular tachycardia. Relation between synchronisation of sensing and origin of the tachycardia.

The feasibility of internal cardioversion for ventricular tachycardia using a prototype of an implantable cardioverter which delivers a low energy discharge via an intracardiac lead and its acceptability to the patient were studied. The cardioverting discharge was synchronised to the apical right ventricular electrogram. In 29 episodes of ventricular tachycardia (RR interval 250-700 ms) the apical electrogram was reliably sensed. The interval from the onset of the QRS complex to the marker of sensing of the electrogram was significantly greater in the 15 episodes arising from the left ventricle than in the 14 episodes arising from the right ventricle; in three cases of ventricular tachycardia arising from the left ventricle the interval exceeded 100 ms. In all cases except one, however, sensing occurred within the first 80% of the QRS complex. In two episodes (RR interval 150 and 190 ms--that is, less than the refractory period of the unit) sensing of the electrogram was unreliable. The unit successfully terminated 10 of 15 episodes of ventricular tachycardia using energies ranging between 0.01 and 1.0 J, but 19 of the 23 discharges delivered to conscious patients caused varying degrees of discomfort. Sensing within 100 ms of the onset of the QRS complex (-20% to 83% of QRS) permitted effective and safe termination of ventricular tachycardia. Although there was neither acceleration of tachycardia nor ventricular fibrillation, subthreshold discharges advanced the next local ventricular electrogram in seven instances. An external low energy cardioverter connected to an intracardiac lead is a useful alternative to repeated external direct current shocks.

Adolescent↗
PubMed1983

Side effects and possible contraindications of amiodarone use.

With the increasing use of amiodarone, several unwanted effects have been recognized. We reviewed 140 patients treated with amiodarone over a 5-year period in an attempt to identify patients at risk, to assess the incidence of these effects and their possible relation to dose, and to determine their outcome. The most common effect was photosensitivity (57% of patients responding to a questionnaire), whereas asymptomatic corneal microdeposits were found in all patients undergoing ophthalmologic examination. In contrast, symptomatic eye changes (colored halos) and slate-gray skin pigmentation were rare. Of the metabolic alterations, the rise in hepatic enzymes correlated with dose and plasma drug and metabolite concentrations (r = 0.59, p less than 0.001; r = 0.62, p less than 0.001, respectively) but was not associated with clinical disease. This relation to dose was not evident in patients developing clinical thyroid abnormalities (two hypothyroidism, two hyperthyroidism), all of whom had normal thyroid function prior to therapy. Four of the five hypothyroid patients were over 70 years of age. No patients developed peripheral neuropathy, but tremor and sleeplessness were common complaints (30% and 28% of patients, respectively) that responded to a decrease in dose. One patient with an abnormal chest x-ray film prior to therapy developed pulmonary fibrosis. We suggest the restricted use of high doses of amiodarone for protracted periods. Patients at particular risk are the older age group (hypothyroidism) and those with abnormal lung function prior to therapy who may be predisposed to pulmonary alveolitis. Most of the observed unwanted effects resolve when amiodarone is decreased in dose or discontinued.

Aged↗
PubMed1983

Clinical value of calcium antagonists in treatment of cardiovascular disorders.

All calcium antagonists have the ability to decrease the symptoms and signs in some patients with ischemic heart disease and help lower the blood pressure in hypertensive persons, but in clinical doses nifedipine does not exhibit antiarrhythmic properties, although these are an important part of the action of verapamil, diltiazem and some substances with a similar chemical structure. In certain disorders beta-adrenergic blocking drugs are useful adjuncts, and under some circumstances, particularly variant angina and supraventricular arrhythmias, specific calcium antagonists are the drugs of choice. More data are needed to define the role of calcium antagonists during cardiopulmonary bypass, in the protection of the ischemic myocardium, in the management of hypertrophic cardiomyopathy and in specific cases of primary pulmonary hypertension. When used with an appropriate sense of perspective and careful observation, calcium antagonists provide useful additional means of helping selected patients suffering from particular cardiovascular diseases.

Adrenergic beta-Antagonists↗
PubMed1983

Acute and chronic haemodynamic and electrophysiological effects of nifedipine in patients receiving atenolol.

The action of nifedipine given first intravenously and then orally was studied in nine patients undergoing investigation for angina pectoris who were already receiving atenolol (100-200 mg/daily) and who had been shown to be fully beta blocked (reduction in maximal heart rate by greater than 25%). Intravenous nifedipine 7.5 micrograms/kg reduced both systolic blood pressure and left ventricular pressure (dP/dt) transiently; both values were significantly lower five and 10 minutes after the infusion of nifedipine but were not significantly different from control values at 20 minutes. There was minimal but pronounced depression of atrioventricular nodal function after giving intravenous nifedipine, though this was detected only when sensitive tests of atrioventricular nodal function were used. These effects were also transient, showing no significant change from control values at 20 minutes. Atrioventricular nodal conduction time and sinus rate were unchanged. Radionuclide angiography of patients taking the oral combination of atenolol and nifedipine for chronic angina showed no change in ejection fraction compared with those taking atenolol alone, but there was a small increase in peak ejection rate. Resting blood pressure and heart rate were unchanged and the PR interval did not lengthen. Peak heart rate and systolic blood pressure showed no alteration on exercise testing when the drugs were combined compared with the response with atenolol alone. Despite the negative inotropic influence when nifedipine was given intravenously, the absence of haemodynamic deterioration when oral nifedipine is combined with atenolol has confirmed that this combination can be used safely in patients with normal left ventricular function. The minimal changes in atrioventricular nodal function cannot be detected on the surface electrocardiogram and are not of clinical importance in patients with normal conduction.

Administration, Oral↗
PubMed1983

The comparative effects of diltiazem and verapamil on atrioventricular conduction and atrioventricular reentry tachycardia.

The electrophysiological effects of diltiazem (0.25 mg/kg), administered by intravenous bolus, have been assessed during intracardiac investigation in 10 patients. Effects on both sinus node and atrioventricular nodal function were measured, as was the influence on reentry atrioventricular tachycardia. There was a tendency for the sinus rate to increase after both diltiazem and verapamil, although with neither drug was this uniform. There was, however, a consistent depression of atrioventricular nodal function with diltiazem which was similar in magnitude to the changes seen after verapamil. With neither drug was there an alteration in His-Purkinje conduction. The drugs had similar effects when given during reentry tachycardia. In six of eight patients, termination occurred, whereas, in the others, both drugs slowed the arrhythmia but failed to terminate it. Diltiazem shows a range of electrophysiological and antiarrhythmic properties similar to those of verapamil. These make it potentially useful for both the acute and chronic treatment of arrhythmias where depression of atrioventricular nodal function is desired.

Adult↗
PubMed1982

Calcium-channel blockers and beta blockers: advantages and disadvantages of combination therapy in chronic stable angina pectoris.

In electrophysiologic studies we have previously shown that the calcium-channel blockers nifedipine, verapamil, and diltiazem have different actions on the atrioventricular node: nifedipine has no evident effect at a dose of 7.5 micrograms/kg of body weight intravenously, whereas verapamil (0.15 mg/kg) and diltiazem (0.25 mg/kg) both prolong the AH interval significantly and terminate or slow reciprocating atrioventricular tachycardia involving the atrioventricular node alone or in association with an accessory pathway. None of the calcium-channel blockers tested influenced intraventricular conduction, but all increased the sinus rate. Since these properties suggested that it would be safer to combine nifedipine, rather than verapamil and diltiazem, with beta-adrenergic blockers in the treatment of ischemic heart disease, we tested this combination for efficacy and safety. Our previous results have now been reviewed, and they show that according to both subjective and objective criteria, nifedipine adds benefits to the action of propranolol in the management of chronic stable angina pectoris. No adverse effects were seen in our series, and beneficial influences were noted in patients with elevation of blood pressure. Side effects reported by others and said to arise from the interaction between nifedipine and beta blockers are analyzed, and prudence is suggested before the combination, or indeed any negative inotropic agent, is given to patients with impaired left ventricular function. The previous reports cannot be taken to indicate that nifedipine has a greater tendency to produce adverse effects in this combination than does the beta-adrenergic blocker.

Adrenergic beta-Antagonists↗
PubMed1981

Potassium supplementation in the treatment of ventricular arrhythmias.

Potassium has a fundamental role in the regulation of the action potential in both myocardial and specialized cardiac cells. The frequency and diversity of ventricular arrhythmia associated with hypokalaemia suggests that potassium also plays a crucial part in the genesis of many cardiac arrhythmias. In addition, the presence of potassium in adequate amounts is required for the effective action of many antiarrhythmic agents. While more information on the mechanism of ventricular arrhythmias in the human is required, as well as observing local biochemical status in the myocardium, it would appear that maintaining the serum potassium towards the upper limit of the normal range offers a logical adjunct to the drug treatment of ventricular arrhythmias.

Action Potentials↗
PubMed1981

Noninvasive recording of the His bundle electrogram: value of supplementary verapamil.

We obtained noninvasive recordings of the His bundle electrogram using the Marquette high resolution MAC unit in 65 patients and 5 normal subjects. Overlap of atrial activity prevented identification of a His potential in 25 subjects, in 23 of whom the PR interval was equal to or less than 160 ms. After intravenous verapamil (10 mg) the AH interval was lengthened, with an increase in the PR interval of 10-60 (mean 20) ms. A characteristic His bundle electrogram was recorded in 48 of the 70; in 8 there was persistent atrial activity and in 4 electrical interference could have obscured a His potential. In 10 patients the absence of a His complex despite a clear "window" of at least 70 ms between the end of atrial activity and the onset of ventricular depolarization suggested that its vector was outside the plane of the electrode arrangement, or that there was a prolonged H-V interval; the latter has been confirmed in 2 patients. Intracardiac His bundle recordings in 25 subjects who had characteristic surface electrical activity of the His bundle disclosed good correlation between invasive and noninvasive measurements of the H-V interval. This noninvasive technique using portable equipment, which permits serial evaluation of the His bundle electrogram, may facilitate prospective studies in patients with conduction disease.

Arrhythmias, Cardiac↗
PubMed1981

Relation between atrioventricular pathways and ventricular response during atrial fibrillation and flutter.

We have analysed the ventricular response as seen on the surface electrocardiogram in patients with paroxysmal atrial fibrillation and flutter in relation to the electrophysiological properties of the corresponding atrioventricular pathways. In 15 patients who had atrial fibrillation with conduction solely through the atrioventricular node, there was a significant correlation between th shortest and mean RR intervals during atrial fibrillation and the functional refractory period, "pre-Wenckebach cycle length", and the shortest ventricular cycle length that resulted from 1:1 atrioventricular conduction. In 18 patients with conduction through an accessory atrioventricular pathway the only good correlation was between the shortest and mean ventricular rate during atrial fibrillation and the "pre-Wenckebach cycle length" and shortest ventricular cycle length during 1:1 atrioventricular conduction. In 12 patients with an atriofascicular bypass tract or rapidly conducting atrioventricular node there was no significant correlation between the RR intervals during atrial fibrillation and the electrophysiological indices; the same lack of correlation was evident in all 11 patients with atrial flutter, all of whom had atrioventricular nodal conduction. The response of atrioventricular pathways to electrophysiological testing, particularly the use of incremental atrial pacing, provides useful guidance in the further management of these atrial arrhythmias.

Adult↗