The value of continuous ECG monitoring during treatment of diabetic ketoacidosis. A computer study

In order to confirm or refute the previously held view that electrocardiographic (ECG) abnormalities are frequent in diabetic ketoacidosis, we have undertaken continuous ECG monitoring for 24 h, with subsequent computer analysis, in 14 diabetic patients admitted with severe ketoacidosis. There was a steady fall in heart rate during the 24-h except in 3 severely dehydrated patients. Depression of the ST-segment was minimal and ST-segment height correlated significantly with heart rate, whereas no consistent relationship was found between T-wave amplitude and either heart rate or plasma potassium. Two patients developed short periods of supraventricular ectopic beats. Although ECG monitoring has been claimed to be a useful aid in the management of diabetic ketoacidosis, this study clearly demonstrates that significant ECG changes are rare and ECG monitoring thereafter adds little to careful clinical observation and regular biochemical assessment.

Mexiletine in the prophylaxis of ventricular arrhythmias during acute myocardial infarction

In a double-blind study involving 165 patients we examined the role of mexiletine, a new antiarrhythmic drug, for the prophylaxis of ventricular arrhythmias after acute myocardial infarction. Mexiletine or placebo was given orally to patients on arrival in the coronary care unit, and continuous electrocardiographic tape recordings were used to document arrhythmias. Ventricular tachycardia and R-on-T ventricular ectopic beats were significantly reduced in the mexiletine patients, but too few episodes of ventricular fibrillation occurred for statistical comment. When arrhythmias did occur in the mexiletine group, it was usually early in the study, at which time plasma drug levels were low. Adverse effects were uncommon. Patients who were given therapy, but in whom acute myocardial infarction could not be confirmed, suffered no serious consequences of taking mexiletine. The results demonstrate the benefit and limitations of prophylactic oral antiarrhythmic therapy for patients with acute myocardial infarction.

Interdose control of beta-blockade and arterial blood pressure during chronic oral labetalol treatment

1 The pharmacological and therapeutic effects of labetalol were investigated during an 8 h interdose period of chronic oral therapy in six patients with essential hypertension. 2 Peak plasma labetalol concentrations were observed 2 h after the morning oral dose, and subsequent decline was mono exponential. 3 Beta-adrenoceptor blockade paralleled the changes in labetalol concentration and was maximal 2 and 4 h after the oral dose. 4 Resting supine systolic BP rose significantly during the interdose period, but no change occurred in diastolic BP. 5 Ambulatory intra-arterial BP studies in a further six patients with essential hypertension controlled with labetalol did not confirm the increase in BP during an 8 h interdose period.

The biological suppression of malaria: an ecological and nutritional interrelationship of a host and two parasites

The interrelationship of malaria and severe ascariasis was studied in Anjouan children with a previously described syndrome of enlarged parotids, localized forehead edema, heavy infestation with Ascaris lumbricoides, and unusual freedom from malaria. After treatment of 37 such children with the ascaricide piperazine, 35 had resolution of parotid enlargement and forehead edema, but 19 developed attacks of malaria. Children treated with placebo had neither resolution of clinical findings nor attacks of malaria. We propose that suppression of the malaria in these children is a nutritional consequence of severe ascariasis and may represent an ecological balance for optimum co-survival of the host and the two parasites.

Studies on intercellular LETS glycoprotein matrices

Intercellular matrices secreted by chick embryo fibroblasts in culture were studied by scanning electron microscopy. Cell-cell contact is a prerequisite for the expression of such matrices. The smallest fiber detected by transmission electron microscopy is 5--10 nm in diameter. These matrix fibers tend to cluster to form bundles. Immunofluorescence and immunoferritin procedures reveal that LETS protein is one of the components of the matrices. The matrices are isolated from other cellular organelles by detergent treatment. More than 90% of the proteins in cell-free matrices are LETS protein, suggesting that the matrices are probably made of only one component--LETS protein. Since the solubilization of matrices requires beta-mercaptoethanol, LETS protein matrices may be the first known polymer system in nature to use disulfide linkage as an intermolecular polymerization vehicle. Collagen does not appear to be involved in such matrices. The LETS protein matrix supports the morphological conversion of rounded cells into spindle-shaped, and also promotes myoblast fusion. It does not, however, exert an effect upon cell growth, the rate of glucose uptake or protease production.

Immediate heart-rate response to standing: simple test for autonomic neuropathy in diabetes

The immediate heart-rate response to standing was measured in 22 normal controls and 25 patients with diabetes, 15 of whom had autonomic neuropathy. The response in the controls and patients without autonomic neuropathy was characteristic and consistent, with tachycardia maximal at around the 15th beat and relative bradycardia maximal at around the 30th beat. The diabetics with autonomic neuropathy, however, showed a flat response. In three controls the response was abolished with intravenous atropine but not with propranolol, showing that it is mediated through the vagus. A simplified test using routine ECGs and measuring the R-R interval at beats 15 and 30 with a ruler is easily performed as an outpatient procedure and may be used as a measure of autonomic function in diabetes.

The value of continuous ECG monitoring during treatment of diabetic ketoacidosis. A computer study

In order to confirm or refute the previously held view that electrocardiographic (ECG) abnormalities are frequent in diabetic ketoacidosis, we have undertaken continuous ECG monitoring for 24 h, with subsequent computer analysis, in 14 diabetic patients admitted with severe ketoacidosis. There was a steady fall in heart rate during the 24-h except in 3 severely dehydrated patients. Depression of the ST-segment was minimal and ST-segment height correlated significantly with heart rate, whereas no consistent relationship was found between T-wave amplitude and either heart rate or plasma potassium. Two patients developed short periods of supraventricular ectopic beats. Although ECG monitoring has been claimed to be a useful aid in the management of diabetic ketoacidosis, this study clearly demonstrates that significant ECG changes are rare and ECG monitoring thereafter adds little to careful clinical observation and regular biochemical assessment.

Peripheral and autonomic nerve function in newly diagnosed diabetes mellitus

Peripheral and autonomic nerve function was assessed in 10 newly diagnosed male diabetics (six insulin-treated and four sulfonylurea-treated) with repeated observations over the subsequent six months. There was significant impairment of motor-conduction velocity in the common peroneal nerve at diagnosis in both treatment groups, with improvement following treatment in only the insulin-treated patients. In contrast, although the blood glucose level fell in both groups, the mean level was significantly lower in the sulfonylurea-treated patients at two months and at each subsequent visit. In the autonomic function tests significant abnormality was found in the electrocardiographic R-R-interval (beat-to-beat) variation in resting heart rate in two of the insulin-treated patients and all of the sulfonylurea-treated group, with improvement in only one of the latter. One patient in the sulfonylurea-treated group also showed an abnormal response to the Valsalva maneuver (expressed as the Valsalva ratio), and this remained abnormal throughout the period of study. All other patients had normal responses to the Valsalva maneuver and sustained handgrip test. None of the patients had postural hypotension. Abnormalities in autonomic nerve function in diabetics at diagnosis have not been previously reported.

Praecordial ST segment elevation. New technique for continuous recording and analysis

The measurement of praecordial ST segment elevation after myocardial infarction is of value in assessing the natural history of ischaemic injury and the effectiveness of intervention. Hand analysis is, however, time consuming and inaccurate. A technique for continuous recording from 35 praecordial leads and subsequent computer analysis is presented, together with illustrative case studies. Changes in body posture and in heart rate are of importance in subsequent data interpretation.

[Frequency and prevention of ventricular arrhythmias after acute myocardial infarct]

In a controlled study using mexiletine and placebo, the incidence of ventricular arrhythmias after acute myocardial infarction (AMI) has been compared. The study covered 40 male patients who had sustained AMI and who in the first 48 h after onset of infarction had exhibited ventricular tachycardia, R on T-, multiform or close-coupled ventricular ectopic beats. Half of the patients were given either mexiletine (250 mg 8-hourly) or placebo. On the 4th and 10th day after onset of infarction a continuous 24-hour ECG was performed. 76% of the patients receiving placebo showed serious ventricular arrhythmias compared with 32% receiving mexiletine (p less than 0.05). These results demonstrate (1) the frequency of ventricular arrhythmias in a group of patients already at risk, and (2) the efficacy of an oral antiarrhythmic agent like mexiletine in the management of these rhythm disorders.

Peripheral and autonomic nerve function in diabetic ketoacidosis

Peripheral and autonomic nerve function was assessed at intervals over a 3-month period in seven diabetics after ketoacidosis. There was marked improvement in motor conduction velocity and terminal latency of both ulnar and common peroneal nerves in all patients. Five had one or more abnormal autonomic function tests but there were no consistent changes during the same period. It is postulated that peripheral nerves may be more susceptible to acute metabolic damage than autonomic fibres.

Interaction between cardiovascular responses to sustained handgrip and Valsalva manoeuvre

Interactions between the cardiovascular responses to the Valsalva manoeuvre and sustained handgrip were analysed in 5 men with untreated mild hypertension and 4 young normal subjects. Though set at a higher level, there was a normal blood pressure response to the Valsalva manoeuvre during concurrent sustained handgrip in 4 of the 5 hypertensive subjects. At the end of the handgrip period in which the Valsalva manoeuvres were performed, the blood pressure was higher and the heart rate lower than in the control period of sustained handgrip. The fifth subject developed a 'square wave' Valsalva response, which returned to a normal response when sustained handgrip was discontinued. Analysis of RR interval changes in the normal subjects showed that both the tachycardia during, and the bradycardia after, the Valsalva strain period were significantly reduced during simultaneous sustained handgrip. These results show that the two reflexes interact, but only to a minor extent, and that the baroreflex response is modified by sustained handgrip, rather than overridden as had previously been suggested. In view of the effect on the blood pressure and heart rate, subjects should avoid performing a Valsalva manoeuvre during sustained handgrip testing.

RR interval variations in young male diabetics

The beat-to-beat (RR interval) variation in resting heart rate was used to detect possible autonomic nerve damage in a group of 42 young asymptomatic male diabetics, employing a sensitive electrocardiographic computer technique. Compared with 25 age-matched controls, the diabetics showed both a significantly smaller mean RR interval (P less than 0.005) and less RR interval variation (P less than 0.001). Whereas only 4 of the diabetic subjects had shorter mean RR intervals, 22 (52%) of the diabetics had RR interval variations that were less than any of the normal subjects. This reduction in heart rate variation has not been previously reported in diabetics without clinical features of autonomic neuropathy and might provide a sensitive method of assessing early autonomic nerve involvement in diabetes.

Comparison of procainamide and mexiletine in prevention of ventricular arrhythmias after acute myocardial infarction

The incidence of ventricular arrhythmias after myocardial infarction has been compared in a controlled study of procainamide, mexiletine, and placebo. Sixty male patients who has sustained a myocardial infarction and had received lignocaine for ventricular tachycardia or ventricular ectopic beats which were R-on-T, multiform, or close-coupled took part. The efficacy of the drugs was evaluated by continuous 24-hour recordings of the electrocardiogram on the 4th and 10th days after admission to the study. Procainamide was given as 500 mg. 4-hourly and mexiletine as 250 mg. 8-hourly with corresponding placebo regimens for 12 days. 77% of patients receiving placebo showed serious ventricular rhythm disorders compared with 33% receiving antiarrhythmic therapy (p smaller than 0.05). Although only 35% of patients receiving procainamide achieved accepted therapeutic plasma concentrations compared with 95% of those receiving mexiletine, both drugs were equally effective antiarrhythmically. The only major adverse effect of therapy noted was development of a positive antinuclear factor in a procainamide-treated patient. These results demonstrate the efficacy of oral antiarrhythmic agents in the management of ventricular arrhythmias after acute myocardial infarction. Mexiletine has the advantage of less frequent administration and lower toxicity.