Phenotype-driven molecular autopsy for sudden cardiac death.

A phenotype-driven approach to molecular autopsy based in a multidisciplinary team comprising clinical and laboratory genetics, forensic medicine and cardiology is described. Over a 13 year period, molecular autopsy was undertaken in 96 sudden cardiac death cases. A total of 46 cases aged 1-40 years had normal hearts and suspected arrhythmic death. Seven (15%) had likely pathogenic variants in ion channelopathy genes [KCNQ1 (1), KCNH2 (4), SCN5A (1), RyR2(1)]. Fifty cases aged between 2 and 67 had a cardiomyopathy. Twenty-five had arrhythmogenic right ventricular cardiomyopathy (ARVC), 10 dilated cardiomyopathy (DCM) and 15 hypertrophic cardiomyopathy (HCM). Likely pathogenic variants were found in three ARVC cases (12%) in PKP2, DSC2 or DSP, two DCM cases (20%) in MYH7, and four HCM cases (27%) in MYBPC3 (3) or MYH7 (1). Uptake of cascade screening in relatives was higher when a molecular diagnosis was made at autopsy. In three families, variants previously published as pathogenic were detected, but clinical investigation revealed no abnormalities in carrier relatives. With a conservative approach to defining pathogenicity of sequence variants incorporating family phenotype information and population genomic data, a molecular diagnosis was made in 15% of sudden arrhythmic deaths and 18% of cardiomyopathy deaths.

Update on cardiopulmonary resuscitation.

Adult cardiopulmonary resuscitation (CPR) has been shown to improve survival for individuals suffering cardiac arrest. Despite this, the delivery of basic life support to victims outside the clinical environment remains poor, particularly as only a minority receive resuscitation. In addition, research continues to examine the optimal techniques for CPR and guidelines have been modified to reflect the latest developments. These guidelines are a compromise between simplicity and effectiveness. While the core of the guidelines remains unchanged, the latest recommendations focus on minimising any delay in the assessment of the collapsed patient and the initiation of CPR. They also address the recent body of opinion promoting compression-only CPR as an alternative to the combined technique of compression and mouth-to-mouth ventilation. Throughout the guidelines a more pragmatic approach to resuscitation is adopted to try to encourage all individuals, whether trained healthcare professionals or lay people, to initiate resuscitation. An acknowledgement of the reasons why individuals may be reluctant to start resuscitation through fear or anxiety will hopefully help to encourage the instigation of these techniques. This overview will summarise the guidelines and highlight alterations or alternatives where appropriate.

Fibrinogen, factor VII clotting activity and coronary artery disease severity.

To asses the relationship between fibrinogen, factor VII coagulant (VIIc) activity and extent of coronary artery disease, we studied 43 white males shown to have greater than 50% stenosis of at least one major coronary artery. Thirty six had a definite history of myocardial infarction at least 3 months earlier and were classified as having 1, 2 or 3 vessel disease while 7 had 2 or 3 vessel disease, but no prior infarction. Groups were similar with regard to age, body mass index and blood pressure. In those with documented prior infarction, there was a significant relationship between the extent of atheroma and coagulation variables factor VIIc and fibrinogen. However, given a similar degree of atheroma, patients with prior infarction had significantly higher levels of factor VIIc activity compared with patients without such a history. These results corroborate those from prospective studies confirming a significant role for the coagulation system in the clinical manifestation of coronary artery disease.

Effects of diazepam and picrotoxin on hyponeophagia in rats.

The effects of diazepam (1 mg/kg), picrotoxin (1.5 mg/kg) and both treatments on hyponeophagia in male and female rats were studied. Diazepam reduced eating latency and enhanced the total amount eaten in the test. Picrotoxin increased approach and eating latencies and reduced amount eaten, females being more sensitive to these actions. Behavioural sensitivity to diazepam was reduced by picrotoxin for approach latency but enhanced for eating latency. These findings are discussed in connection with the GABA hypothesis of the actions of benzodiazepines.

Effects of diazepam and of serotonin agonists on hyponeophagia in rats.

The effects of serotonin agonists, fenfluramine (2 mg/kg) and 5-methoxy N,N dimethyltryptamine (5-MeODMT, 2.5 mg/kg) on hyponeophagia were studied both alone and in combination with diazepam (1 mg/kg). Male and female rats were used but sex differences were not found. The serotonin agonists enhanced hyponeophagia while diazepam attenuated it and antagonised the actions of both serotonin agonists. These findings are discussed in connection with the serotonin hypothesis of benzodiazepine action with the conclusion that diazepam acts distally to serotonergic drugs on hyponeophagia.

The effects of parachlorophenylalanine and stimulus intensity on open-field test measures in rats.

An inhibitor of 5-hydroxytryptamine synthesis, p-chlorophenylalanine (PCPA), or an inert saline solution was administered intraperitoneally to rats. At maximum depletion of serotonin (72 hr after injection), the rats were tested in the standard, four-day open-field test. A further four days of testing in the open field in which the sound level was raised from the standard 78 to 93 dB showed that, while PCPA increased defaecation in both sexes and under both sound levels, the controls increased defaecation at the higher level stimulus intensity, whereas PCPA-injected rats defaecated less. Parachlorophenylalanine increased ambulation in males on the first day of open-field testing but not in females. On the remaining seven days of testing PCPA markedly reduced ambulation in females but did not affect ambulation in males. Across-trial habituation of neither the defaecation nor the ambulation measure was influenced by PCPA.

Drug interactions do not support reduction in serotonin turnover as the mechanism of action of benzodiazepines.

Interactions between 5-methoxy, N,N-dimethyltryptamine (5-MeODMT), chlordiazepoxide and para-chlorophenylalanine (pCPA) on conflict behaviour were studied. 5-Methoxy, N,N-dimethyltryptamine (1.0 and 3.0 mg/kg), induced observable effects and reduced unpunished response rates but did not affect punished behaviour either alone, on in the presence of 5 or 10 mg/kg chlordiazepoxide. However, 5-MeODMT (1 mg/kg) reversed the anti-conflict effects of chronic administration of pCPA (100 mg/kg). Chronic administration of pCPA did not prevent the increase in punished response rates induced by chlordiazepoxide (5 mg/kg). These findings are discussed in the context of the serotonin hypothesis of benzodiazepine action, with the conclusion that benzodiazepines act at a site distal to that of serotonergic drugs on conflict behaviour.

Clinical validation of a miniature nuclear probe system for continuous on-line monitoring of cardiac function and ST-segment.

A new, miniature cesium iodide/photodiode nuclear probe (the "Cardioscint") has been developed for continuous on-line measurement of left ventricular function and the ST-segment. Ejection fraction (EF) measurements in 77 patients were compared with gated equilibrium radionuclide ventriculograms. The probe was positioned over the left ventricle by first using a blind positioning algorithm and then by using the gamma camera. Background was measured both manually and automatically. There was good correlation between probe (positioned blind) and gamma camera EF with both manual (r = 0.80, n = 65) and automatic (r = 0.78, n = 66) backgrounds. Use of the gamma camera did not significantly alter the results. Correlation between the probe stroke counts and thermodilution-derived stroke index during atrial pacing in six subjects was also satisfactory (r = 0.69, n = 102). Thus, the Cardioscint is able to provide a reliable estimate of EF and can track rapid changes in cardiac volumes.

Value of carvedilol in congestive heart failure secondary to coronary artery disease.

Despite considerable interest in the use of beta-blocking agents in congestive heart failure (CHF), their clinical application is limited because of their negative inotropic effects. Beta blockers with vasodilating properties may have the advantage of overcoming this, however. Carvedilol, a beta-blocking agent with vasodilating properties, was evaluated in 17 patients with chronic CHF secondary to ischemic heart disease with a resting left ventricular ejection fraction less than or equal to 45%, who were being maintained on diuretics. Exercise testing, radionuclide ventriculography, and right-sided cardiac catheterization were performed and intraarterial blood pressure measured before and after 8 weeks of carvedilol therapy in a dosage of 12.5 to 50.0 mg twice a day. Twelve patients completed the study and 5 withdrew. Symptomatic and hemodynamic improvement was demonstrated in 11 of the 12 patients. Heart rate and intraarterial blood pressure were both reduced by chronic therapy. Mean +/- standard deviation exercise time improved from 4.3 +/- 1.6 to 7.1 +/- 2.7 minutes (p less than 0.0001), as did resting left ventricular ejection fraction, from 27 +/- 9 to 31 +/- 11% (p less than 0.02). Pulmonary arterial wedge pressure fell from 19 +/- 7 mm Hg to 12 +/- 5 mm Hg (p less than 0.001) and total systemic vascular resistance from 1,752 +/- 403 to 1,497 +/- 310 dynes/s/cm-5/m2 (p less than 0.02). Stroke volume index improved also, from 31 +/- 6 ml to 40 +/- 6 ml (p less than 0.0005). These hemodynamic changes were mediated partly by vasodilation, diminished myocardial oxygen demand and reduction of sympathetic overactivity in the failing heart. These data suggest that carvedilol may have beneficial effects in patients with chronic CHF secondary to coronary artery disease.

Effectiveness of the once-daily calcium antagonist, lacidipine, in controlling 24-hour ambulatory blood pressure.

The efficacy of the new once-daily dihydropyridine calcium antagonist, lacidipine, in reducing ambulatory intraarterial blood pressure (BP) was examined in 12 untreated hypertensive patients. The intraarterial recording was commenced 24 hours before the first 4-mg dose and was continued for a further 24 hours thereafter. After dose titration and chronic therapy, a second 24-hour ambulatory BP recording was made. There was a steady onset of drug action, maximal at 2 hours, but with reflex tachycardia after the first dose. Chronic administration reduced BP throughout the 24-hour period, without tachycardia. Mean daytime reduction in BP was 20 mm Hg systolic (p less than 0.005) and 12 mm Hg diastolic (p less than 0.02). Mean nighttime reduction was 8-mm Hg systolic (p less than 0.05) and 6-mm Hg diastolic (difference not significant). There was no postural decrease in BP on 60 degrees head-up tilting and hypotensive action was maintained during isometric exercise (reduction at peak of 32/18 mm Hg, p less than 0.05) and throughout dynamic exercise (reduction at peak of 23/14 mm Hg, p less than 0.05). Lacidipine is an effective once-daily antihypertensive agent, with good control of stress response.

Hyponeophagia and arousal in rats: effects of diazepam, 5-methoxy-N,N-dimethyltryptamine, d-amphetamine and food deprivation.

A modified hyponeophagia test is described as an animal model of anxiety. The effects of 0, 0.3, 1.0, 3.0 and 10 mg/kg diazepam, given both acutely and for 7 days pretest, were assessed in rats. Acutely, diazepam reduced hyponeophagia over the dose range 0.3-3.0 mg/kg but 10.0 mg/kg produced sedation and large variability. Chronically, the dose-response relationships were monotonic and the maximal effect was increased, suggesting that differential tolerance occurs to the sedative, but not to the anxiolytic, effects of this drug. Increased food deprivation did not mimic benzodiazepine effects on hyponeophagia, and actually prolonged eating latency in rats treated with 5-methoxy-N,N-dimethyltryptamine (2.5 mg/kg), which does not support an interpretation of diazepam effects in terms of appetitive actions. An arousal hypothesis of hyponeophagia was proposed and supported by the antagonism of the sedative effects of 10.0 mg/kg diazepam by d-amphetamine (0.5 mg/kg). Although both male and female rats were used throughout, sex differences were few in these studies.

Hyponeophagia in the Roman rat strains: effects of 5-methoxy-N,N-dimethyltryptamine, diazepam, methysergide and the stereoisomers of propranolol.

The effects of 5-MeODMT (2.5 mg/kg), diazepam (1 mg/kg), methysergide and the stereoisomers of propranolol (6 mg/kg) on hyponeophagia were studied in both sexes of the Roman strains of rats, selectively bred for acquisition of a two-way conditioned avoidance response. Diazepam, methysergide and 1-propranolol increased feeding in a novel environment whilst 5-MeODMT decreased it and d-propranolol was inactive. Several strain differences in drug responsiveness occurred, the Roman Low Avoidance subjects being most sensitive to all drugs tested as well as being most neophobic. A sex difference in 5-MeODMT sensitivity was also found, female rats of the Roman High and Control Avoidance strains being more sensitive than males. The findings are discussed in connection with differences in arousal and biochemical parameters between these strains.

Sex and strain differences in benzodiazepine receptor binding in Roman rat strains.

Specific [3H]flunitrazepam binding was determined for five brain regions in both sexes of the three Roman rat strains. Small strain differences and a large Sex-Region interaction were detected, benzodiazepine receptor binding being significantly higher in females in the two cortical areas and the cerebellum, but significantly lower in the striatum and hippocampus. These findings are discussed in the context of sex and strain differences in behavior and benzodiazepine sensitivity.

Intra-arterial monitoring of the antihypertensive effects of once-daily amlodipine.

Amlodipine is a dihydropyridine calcium antagonist with a long elimination half life making it suitable for once-daily dosing. This study used sphygmomanometric and intra-arterial ambulatory blood pressure (BP) monitoring to confirm the antihypertensive effect of a once-daily dose of amlodipine over the dosing interval. After a 2-week single-blind placebo run in, amlodipine was administered to 11 patients at a starting dose of 5 mg daily for 2 weeks increasing to 10 mg daily for a further 4 weeks if diastolic blood pressure (DBP) measured sphygmomanometrically was not < 90 mmHg or decreased by > 10 mmHg from baseline values. Intra-arterial blood pressure recordings for 24-hour periods were made at the end of the placebo run in and on completion of the active treatment phase. The effects of isometric and dynamic exercise and head-up tilting (60 degrees) on BP and heart rate were measured during ambulatory monitoring. Mean supine cuff BP was 169/104 mmHg (n = 11) at the end of the placebo treatment period and was reduced to 153/95 mmHg (n = 11) after 2 weeks of amlodipine treatment and 146/92 mmHg (n = 11) after 6 weeks of amlodipine treatment. There was no significant change in heart rate. Intra-arterial ambulatory monitoring showed that BP was controlled for the whole dosing interval with once-daily doses of amlodipine. The normal circadian pattern of BP changes was not altered. BP was reduced by amlodipine during exercise and physiological tests, but there was no postural hypotension and the BP and heart rate responses to exercise were not blunted.(ABSTRACT TRUNCATED AT 250 WORDS)

Activity of cardiac enzymes measured in the coronary sinus in acute myocardial infarction.

Three patients with acute infarction of the anterior wall of the heart underwent catheterisation of the coronary sinus. Samples were taken for estimation of activity of cardiac enzymes. A small gradient was demonstrated between the sinus and the venous blood, suggesting that the coronary sinus is the conduit by which these enzymes are liberated into the systemic circulation.

Beta-adrenoceptor antagonists may attenuate hyponeophagia in the rat through a serotonergic mechanism.

The unconditioned inhibition of feeding in a novel setting (hyponeophagia) was reduced by propranolol and another potentially centrally acting beta-adrenoceptor antagonist, pindolol but not by a peripherally acting one, atenolol. A similar attenuation of hyponeophagia was seen following the 5-HT antagonist methysergide but no consistent effects were observed following some dopamine antagonist drugs. 5-Methoxy N,N-dimethyltryptamine (5-MeODMT), a compound with central 5-HT agonist properties, consistently potentiated hyponeophagia, an effect which was reversed by the centrally acting beta-adrenoceptor antagonists and by methysergide. The results are interpreted as evidence for a 5-HT mediation of hyponeophagia and for a probable central 5-HT antagonist role for propranolol and pindolol.

Relationships between hyponeophagia, diazepam sensitivity and benzodiazepine receptor binding in eighteen rat genotypes.

Rats of 18 genotypes derived from the selected Roman strains were tested for hyponeophagia in a control condition and following diazepam (1 mg/kg). Subsequently, benzodiazepine receptor binding was measured in the cortical/striatal region. Hyponeophagia in the control condition correlated strongly with diazepam sensitivity, but benzodiazepine receptor titres did not correlate significantly with either control behavior or drug responsivity. These findings are discussed in the contexts of the arousal hypothesis of hyponeophagia and of postulated relationships between benzodiazepine receptors and emotionality.

111In-antimyosin antibody imaging for detection of myocardial infarction: a quantitative approach.

Indium-111-antimyosin imaging has been shown to be a sensitive and specific method for detecting myocardial necrosis, but a quantitative method for interpretation of 111In-antimyosin planar images is lacking. A prospective study was performed in 114 patients with suspected acute myocardial infarction using planar 111In-antimyosin imaging. A ratio of maximum myocardial uptake counts (H) (9 X 9 pixels) over adjacent lung background (L), i.e. H/L ratio, was obtained from 24 and 48 h images. This value was compared with peak creatine kinase (CK) enzyme and left ventricular ejection fraction (LVEF). The patients were classified into groups based upon standard criteria for Q-wave acute myocardial infarction (Q-MI) (n = 50), non-Q-MI (n = 21), unstable angina (n = 15) and those with no evidence of MI or ischaemia (n = 28). The mean +/- S.D. H/L ratio in the Q-MI group was 2.28 +/- 0.50 (24 h, left anterior oblique, LAO, view) and was greater than the non-Q-MI group (1.98 +2- 0.30) (P less than 0.02). In patients with unstable angina (UA), seven had a high ratio (1.75 +/- 0.29) and eight had a lower ratio (1.29 +/- 0.07). In the group of patients without MI or UA, the ratio was 1.24 +/- 0.11 and this was significantly lower than the Q-MI and non-Q-MI groups and those patients with UA and positive 111In uptake (P less than 0.001, respectively). However, there was no significant difference between old MI and patients without evidence of MI or UA.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous variability of left ventricular ejection fraction assessed with the Cardioscint.

A miniature, non-imaging caesium iodide nuclear probe optically coupled to a photodiode (the 'Cardioscint') has been developed which, in conjunction with a modified personal computer, is capable of continuous on-line monitoring of left ventricular function and ST-segment level at the bedside. The purpose of this study was to assess the variability in ejection fraction over periods of time and to compare this variability with that of equilibrium gamma camera radionuclide ventriculography. Ten normal volunteers (nine male) of mean (S.D.) age 49 (10) years underwent semisupine radionuclide ventriculography using both gamma camera and Cardioscint in randomized order. The gamma camera recorded four consecutive acquisitions (mean of 7.2 min each) and the Cardioscint, using a 20 s acquisition time, recorded left ventricular function over 35 min per subject. The mean ejection fraction of the group by gamma camera was 52 (7)% and by Cardioscint was 54 (5)%. When the variability in ejection fraction by gamma camera was compared with the Cardioscint averaged over corresponding time periods (i.e. an average of 7.2 min), the mean coefficient of variation of the camera was 5.0% versus 2.9% for the probe system. Individual 20-s probe acquisitions over the total study duration (reflecting the short-term variability of the system) had a coefficient of variation of 5.1%. Thus the Cardioscint provides a stable continuous recording of ejection fraction. These volunteer data provide a basis for interpretation of data acquired in the clinical situation.