Number Of Extrasystoles Research Articles

Power modulation spectrum – a promising approach for the indispensable quality control of electrocardiogram signals from monitoring units for the detection of autonomic dysfunction

ObjectiveElectrocardiogram (ECG) is essential for evaluating the autonomic nervous system. Ensuring the quality of real-world ECG datasets is critical, but manual control of large datasets is impractical. Thus, automated quality control is necessary. This paper introduces a new quality index, the peak-distance quality index (PDQI), based on the modulation spectrum approach. MethodsReal-life data from 1000 ECG recordings, each 600 s long, were collected at the stroke unit of the University Hospital Tulln. Each ECG was visually evaluated, including the duration of the signal, artefacts and noise, and the number of extrasystoles. The power-modulation spectrum, the percentage of ECG in each signal, and modulation spectrum-based quality index (MS-QI) and PDQI were calculated. The area under the curve (AUC) for the detection of high-quality ECGs was calculated for both quality indices, as well as the optimal threshold for each index. ResultsThe percentage of ECG signals in the recordings based on the modulation spectrum correlates with expert rating (r = 0.99, p < 0.001). The AUC for PDQI for the detection of extrasystoles is 0.96, and the AUC for MSQI for the detection of artefacts is 0.83. The optimal thresholds for PDQI and MSQI are 0.44 and 0.17, respectively ConclusionThe power modulation spectrum can be applied to large amounts of data to detect ECG signals within biosignals and calculate quality indices. MSQI can be used for artefact detection and PDQI for extrasystole detection in ECG signals. A combined approach using both quality indices can provide a picture of the underlying data quality.

Therapy of dysrhythmias in young women with estrogen deficiency, arterial hypertension, and "metabolically healthy" abdominal obesity

Objective. To study the frequency and type of dysrhythmias in young women with arterial hypertension (AH), hypoestrogenemia and «metabolically healthy» abdominal obesity (MHAO), as well as the efficacy of antiarrhythmic drug Allaforte in this cohort of patients. Material and methods. The study included 29 patients with AH, hypoestrogenemia and MHAO, who received the antiarrhythmic drug Allaforte in standard therapy. Patients were comparable in age, severity of course and duration of AH, and therapy. At the beginning of the study and after 4 months of therapy with Allaforte the patients underwent 24-hour ECG Holter monitoring. Results and conclusion. When analyzing the nature and structure of dysrhythmias, it was found that supraventricular extrasystoles, including frequent and allorhythmic ones, are quite often registered in women with AH, estradiol deficiency and MHAO. Similar trends can be traced with respect to the frequency of ventricular arrhythmias. The inclusion of Allaforte in the therapy contributes to the decrease in the number of extrasystoles, normalization of heart rhythm and improvement of general well-being of the patients.

Evaluation of the effect of extrasystolic arrhythmia in pregnant women on fetal condition

Relevance much attention is paid to the problem of the effect of extrasystolic arrhythmia in pregnant women on the condition of the fetus. The aim of the study is to study the effect of extrasystolic arrhythmia in pregnant women on the condition of the fetus by cardiotocography. Material and methods. 32 pregnant women with extrasystole (group 1) and 30 without arrhythmia (group 2) were examined in the 3rd trimester from the 32nd week of pregnancy. All pregnant women of both groups underwent daily registration of electrocardiography (ECG), ultrasound examination of the heart, fetal cardiotocography (CTG of the fetus), determination of the level of human chorionic gonadotropin (hCG), prolactin and thyroid hormones. Results. The correlation analysis revealed a close relationship between the number of fetal cardiotocography scores and the level of thyroid-stimulating hormone (TSH) (r = 0,917, p &lt;0,01), free thyroxine (T4c) (r = -0,877, p &lt; 0,01) and the number of extrasystoles (r = -0,872, p &lt; 0,01) in pregnant women. Conclusion. In pregnant women with and without extrasystole, there are differences between reproductive hormones and electrocardiography indicators within the reference values. It was found that in pregnant women with and without extrasystole, fetal cardiotocography indicators do not significantly differ. A quantitative threshold value of ventricular extrasystole was revealed to reduce the number of fetal cardiotocography scores in the third trimester from week32. The threshold value of extrasystole was 1500 per day, AUC (area under curve) – 0,792, sensitivity – 81,3 %, specificity – 100,0 %.

Тонзиллярная проблема и ее сердечно-сосудистые аспекты на современном этапе

A comparative assessment of the characteristics of myocardial and vascular damages as well as their occurrence in patients with decompensated chronic tonsillitis (CT) sent to the hospital for planned tonsillectomy were carried out. 179 people aged 18 to 25 years were examined. Two groups were formed: group 1: patients with decompensated СT (102 people) and group 2: control – that is, persons without СТ (77 people). We used 24-hour ECG monitoring (Holter) with a set of additional diagnostic options and EchoCG to determine various characteristics of myocardial activity. The arterial wall was assessed using indicators of vascular stiffness and assessment of blood pressure balance in the vascular territories. We used hardware-diagnostic complexes DMS Advanced Technologies (Russia) and RuSkan-70P (Russia). Myocardial damage was judged by exceeding the upper limit of the permissible norm for such indicators as the number of extrasystoles per hour, the maximum rate of increase in pressure in the aorta (dP/dTmax), and the size of the heart chambers; and damage to the vascular wall was judged by similar changes for the aortic pulse wave (PWVao), aortic reverse pulse wave augmentation index (AIx ao), and ankle-brachial index (ABI). The individual profile of the main cardiovascular risk factors was also assessed. Data processing was carried out using the Statistica 10.0 software package (StatSoft Inc., USA). The results indicated the presence of a negative effect of СТ not only on the myocardium with the development of some moderate changes but also on the vascular wall. The latter violations were recorded significantly more often. Vascular disorders were characterized by increased arterial stiffness and pressure imbalance within the framework of preclinical arterio- and atherosclerosis. It is necessary to develop targeted angioprotective measures with СТ and their inclusion in the comprehensive process of managing this category of patients, including in the preoperative period. Therefore, the management of such patients should be based on the principles of effective interdisciplinary cooperation.

PERFORMED FACTORS IN THE REHABILITATION OF CARDIAC PATIENTS ON AN OUTPATIENT BASIS

In older people, adequate pharmacological tactics when using modern antihypertensive drugs and their combinations, which provide maximum cardiovascular protection, can increase the duration and improve the quality of life, significantly reduce the likelihood of complications. An increase in the tone of the sympathetic nervous system leads to biliary dyskinesia by hypokinetic type, an increase in blood pressure.&#x0D; The aim is to optimize the treatment of patients with high blood pressure, rhythm disturbances, to analyze the possibility of using Poltava's Bischofite mineral compound, dietary magnesium-mineral supplements Bisheffect, in the complex treatment of hypertension for internal use.&#x0D; Matherials and methods. 68 patients with arterial hypertension with concomitant hepatobiliary pathology, which was confirmed by clinical and instrumental research methods, were under observation. The patients’ mean age was 47.9 ± 2.9 years. The analysis of heart rate variability was carried out during a test with physical activity on a bicycle ergometer with “Cardiolab+” equipment (“XAI-Medica, Kharkiv, Ukraine). In addition, daily monitoring of blood pressure was carried out using the ABPM-04 - Meditech apparatus.&#x0D; Result. By the end of the first week of treatment, most patients (82.34%) noted a significant improvement in well-being. During bicycle ergometry, autonomic nervous system stabilisation, blood pressure normalisation, a decrease in the number of extrasystoles, the sleep and the stool normalisation were recorded. The reason for the failure of standard antiarrhythmic therapy in this group of patients was determined based on the studies. Such a problem was observed due to dysfunction of the autonomic nervous system, which is an integral companion of the pathology of the gastrointestinal tract. This concept involves expanding the diagnostic search and stimulates the search for new ways of rhythm disturbances treatment in the pathology of the gastrointestinal tract. Also, the indices of blood pressure variability have decreased. Average 24h blood pressure in patients on the 10th day of treatment decreased by an average of 25-35 mm Hg, and there was a decrease in cranialgia attacks and autonomic disorders. An increase in the blood ejection fraction by 34%, a heart's stroke volume by 19%, and a normalisation of the minute volume (p˂0.05) were revealed, which confirms the positive effect of bischofite-therapy in the complex treatment of cardiac pathology.&#x0D; Conclusions. Treatment with standard LEIT-therapy, use of dietary magnesium-mineral Bisheffect supplements resulted in the autonomic nervous system stabilisation, blood pressure normalisation, a decrease in the number of extrasystoles, the sleep and the stool normalisation, increased exercise tolerance.

Impact of ranolazine on exercise tolerance and arrhythmias in patients with INOCA

The aim of the study to evaluate the effect of supplementation of basic therapy by ranolazine in patients with INOCA on exercise test parameters and Holter ECG monitoring.&#x0D; Materials and methods. 53 patients with stable coronary heart disease were examined, including 18 men (33.9 %) and 35 (66 %) women, the average age of patients was 57 (±9.68) years. According to the results of coronary angiography all patients had non-obstructive coronary arteries. In addition to physical and laboratory examination, bicycle ergometry, Holter ECG monitoring and echocardiography were included in the examination of patients. Patients were divided into 2 groups: group I - patients who in addition to standard therapy received ranolazine at a dose of 1000 mg twice a day for 6 months, and group II patients with standard coronary heart disease therapy. After 6 months from the beginning of the observation an objective examination, echocardiography, exercise test, Holter ECG monitoring were repeated.&#x0D; Results. The study found that patients receiving ranolazine in addition to standard therapy had a statistically significant increase in exercise duration after 6 months compared with baseline and group II. Before treatment in group I, the duration of the exercise test was 356.51±180.24s, and after treatment 414.32±142.10s (p=0.03). In group II, the duration of the test before treatment was 361.4±160.24 c, and after 380.5±152.2 s (p=0.15). It was also found that the duration of the test differed significantly in group I after treatment of patients from group II after treatment of patients with a standard treatment regimen (p=0.04). According to the results of Holter ECG monitoring in group I found a positive effect of ranolazine on the frequency of ventricular arrhythmias: before treatment n=1142 [30; 2012], after treatment n=729 [23; 1420], while in group II a significant difference between the number of extrasystoles before treatment and after not detected (n=1026 [17; 1920], n=985 [15; 1680], respectively) p=0.18.&#x0D; Conclusions. The addition of ranolazine to the basic therapy of patients with non-obstructive coronary arteries disease helps to increase exercise tolerance (according to the loading stress test) and contributes to a significant reduction in the number of ventricular arrhythmias (according to Holter-ECG) compared with both baseline and group II

Melatonin Treatment Does Not Modify Ectopic Activity During Ischemia and Reperfusion in Rats

Introduction Ventricular tachycardia and/or ventricular fibrillation (VT/VF), a life-threatening complication of acute myocardial ischemia are based on the interaction between a vulnerable arrhythmogenic substrate and an arrhythmic trigger. Melatonin was proposed as a potential antiarrhythmic medication and was shown to ameliorate the arrhythmogenic substrate. Also, melatonin provides a sympatholytic effect and thereby can attenuate ectopic activity, which provides the triggers for VT/VF. However, little is known about a melatonin effect on the arrhythmic triggering. In the present study, we aimed at evaluation of the melatonin effects on catecholamine synthesis in normal and ischemic myocardium and heart rhythm disturbances during an episode of ischemia and reperfusion. Methods Experiments were done in 30 control and 32 melatonin-treated (10 mg/kg, daily, for 7 days) male rats. The hearts from 10 control and 10 treated animals were taken for histochemical analysis of sympathetic fibers (glyoxylic acid-induced fluorescence). Continuous ECG recording was performed in 20 control and 22 treated anesthetized animals before and during an ischemia-reperfusion episode induced by reversible 5-min occlusion of the left anterior descending coronary artery. Tyrosine hydroxylase expression in normal and ischemic myocardial regions was assessed by Western blotting analysis in 12 control and 12 melatonin-treated animals. Results No differences in the state of sympathetic innervation (density and fluorescence intensity) were observed in histochemical analysis. However, Western blotting demonstrated that melatonin treatment suppressed tyrosine hydroxylase expression in normal (p<0.05 vs control) but not in ischemic regions of myocardium. Melatonin-treated animals had longer RR-intervals in the baseline state, but this difference progressively disappeared during the period of ischemia due to tachycardic response to ischemia in the treated group (Figure). No differences in the number of extrasystoles were found between the control and treated groups during ischemia and reperfusion periods (Figure). Conclusion Chronic melatonin treatment led to the peripheral sympatholytic effect in myocardium, which was associated with decreased heart rate in preischemic conditions. However, this effect attenuated during ischemia and no differences in heart rate or extrasystolic burden were found between the control and treated animals during ischemia and reperfusion.

Risk of heart rhythm disorders in patients with chronic obstructive pulmonary disease, combined with ischemic heart disease during computer spirography

The aim — to evaluate the safety of spirography with bronchodilation test in patients with a combination of stable ischemic heart disease (IHD) and chronic obstructive pulmonary disease (COPD).Materials and methods. 148 patients were examined including 53 patients with a combination of stable IHD and COPD, 53 IHD patients without concomitant COPD and 42 patients with COPD. Patients underwent general clinical examination, monitoring of an electrocardiogram, echocardiography, spirography.Results and discussion. An increase in the number of extrasystoles within 1 hour after performing spirography was noted, the greatest increase in the number of supraventricular extrasystoles (SVE) was observed in patients with combined pathology — on average (12.6 ± 6.8, p = 0.23). The number of ventricular extrasystoles (VE) within 1 hour after spirography in patients with combined pathology increased by (27.8 ± 12.6, p = 0.0064), whereas in patients with IHD — by (3.4 ± 2.2, p = 0.19), in patients with COPD — by (15.7 ± 12.5, p = 0.076). An increase in the number or occurrence of polytropic VE was reported in 4 (7.5 %) persons with combined pathology, in 2 (3.8 %) patients with IHD and in 3 (7.1 %) patients with COPD. The occurrence of high‑grade VE during spirography was established in 11 (20.7 %, p = 0.008) patients with a combination of IHD and COPD, in 5 (9.4 %, p = 0.06) patients with isolated course of IHD and in 3 (7.1 %, p = 0.23) patients with COPD. The predictors of an increase in the number of VE within 1 hour after performing spirography for patients with IHD and COPD were identified.Conclusions. Spirography is associated with the occurrence of rhythm disorders in patients with a combination of IHD and COPD. Prior to spirography, patients with IHD should undergo echocardiography and daily monitoring of the electrocardiogram.

FUNCTIONAL CONDITION OF THE CARDIOVASCULAR SYSTEM IN CHILDREN WITH TYPE 1 DIABETES DEPENDING ON THE LEVEL OF GLYCEMIA

Purpose of the study: to determine main parameters of the heart rhythm in children with type 1 diabetes, depending on the night level of glycemia. We performed bifunctional monitoring of glycemia and ECG in 50 patients with type 1 diabetes from 10 to 17 years. Depending on the glycemic parameters summarized in all patients we divided 3 groups: Group 1 (n=11) – sites of hypoglycemia (≤3.9 mmol/l), Group 2 (n=35) – optimal level of glycemia (4.0-9.0 mmol/l) and Group 3 (n=45) – sites of hyperglycemia (&gt; 9 mmol/l). According to the results of glycemic monitoring, 96% of children do not have glycemic target marks at night and 20% of patients have asymptomatic night hypoglycemia. When analyzing the parameters of Holter ECG monitoring, the greatest value of heart rate, duration of the QTc interval, as well as atrial ectopic activity were often recorded during periods of hypoglycemia. Hyperglycemia also causes pathologic elongation of the ventricular electric systole and a greater number of ventricular extrasystoles. Thus, night hypo- and hyperglycemia in children and adolescents with type 1 diabetes leads to an extension of the QTc interval, an increase in the number of extrasystoles with the highest severity and frequency in hypoglycemia. We noted a high level of functioning of the sympathetic department of the autonomic nervous system and the central contour of heart rhythm regulation in children and adolescents with type 1 diabetes mellitus in hypoglycemia.

Пусковые факторы и поддерживающие механизмы экстрасистолии и наджелудочковой тахиаритмии у небеременных и беременных женщин

The frequency of occurrence, trigger factors, supporting mechanisms of arrhythmia and paroxysmal supra-ventricular tachyarrhythmias in non-pregnant and pregnant women were studied. The study involved 26 non-pregnant women aged 18 to 29 years (25,8+2.2 years) and 30 pregnant women from 20 to 32 years (25,6+2,8) without complaint and without structural heart disease. Holter monitoring of ECG and transesophageal electrophysiological study of the heart were performed in all patients. It is revealed that there are arrythmia and paroxysmal supra-ventricular tachycardia in pregnant women more often than in non-pregnant. Reducing the number of extrasystoles and paroxysmal supra-ventricular tachyarrhythmias occurs 6 months after birth. It is established that in non-pregnant and pregnant women there are four types of curves atrio-ventricular conduction (AVC): continuous, intermittent, continuous with the phenomenon of the &amp;#34;gap&amp;#34;, intermittent with the phenomenon of the &amp;#34;gap&amp;#34;. The continuous curve type of AVC is detected in non-pregnant women, in pregnant women – intermittent, in women six months after childbirth - continuous. It is proved that the electrophysiologi-cal substrate curves atrio-ventricular conduction is retrograde functioning additional channel and longitudinal dissociation of atrio-ventricular connections on the fast and slow ways.

Circa-and ultradians in the occurrence of simple extrasystoles in healthy men at lowland in the light of inferential statistics

An exact description of circadian and ultradian rhythms of simple extrasystoles in healthy subjects is lacking. Thirty-seven healthy male subjects, aged 50-76, were randomly taken. Simple extrasystoles from 24-hour Holter ECG were registered and calculated per each hour and processed by cosinor regression. Their occurrence is formulated by 95% confidence and tolerance corridors for supraventricular and ventricular extrasystoles. The number of extrasystoles is relatively low, dispersion of ventricular extrasystoles is significantly higher than supraventricular ones. A significant increase of their frequency versus the general zero trend straight line was found only around 9 a.m. In supraventricular ones a significant increase around 6-7 a.m., 9 a.m., noon, and 4-5 p.m. and a significant depression around 1-2 a.m. and 10 p.m. was present. Only the 24-hour rhythm is significantly present (alpha=0.05) in ventricular beats while in supraventricular ones also the period lengths of 12, 6, 4, 3.4 and 2.4 hours are significant. The significant difference between supraventricular and ventricular extrasystoles exists in the 24-hour amplitudes and 6-hour acrophases. One circadian and several ultradian rhythms of simple extrasystoles are present in healthy male subjects over 50 years of age. The 95% tolerance chronograms can be exploited in clinical practice.

Functional capacity of the cardiovascular system of elderly people as estimated by heart rate variability

With the aid of mathematical and spectral analysis of the heart rate (HR) wave structure in a dynamic interval tachogram (TG) in elderly subjects, it has been shown that a stable sinus rhythm is typical of the majority of the indigenous population of the rural areas of the North aged 78–97 years and migrants living in the city of Vorkuta aged 60–88 years. The total RR-interval spectrum power (800 ± 98 ms2) in the TGs of the native population is shifted to the very low frequency band (VLF, 52%), which indicates predomination of the humoral-metabolic HR regulation level. The reaction to orthostatic load in elderly subjects is characterized by a significant increase in the total spectrum power, which indicates changes in the autonomic balance of regulation of the wave structure of the HR variability. A low total spectrum power (609 ± 104 ms2) with a predominance of low frequency (LF) waves in the TGs of the migrants at rest reflects the activity of the sympathetic component of HR regulation. The reduction of the parasympathetic regulation and the growth of the sympathetic activity during an active orthostatic test in the migrants is a predictor of cardiovascular diseases. In individual TGs of recipients with HR disorders, the orthostatic test (the redistribution of blood flow in the main vessels) results in a decrease in the number of extrasystoles due to the specific features of the baroreflex regulation mechanisms of the cardiovascular system. The HR variability has been shown to be an indicator of the functional capacity of the cardiovascular system in elderly subjects.

EFFECT OF BRONCHODILATORS ON HEART RATE VARIABILITY IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Aim. To study effect of long-acting theophylline (Theotard, KRKA) and combination of salmeterol and fluticasone (Seretide, GlaxoSmithKline) on heart rhythm variability (HRV) and number of arrhythmic episodes in patients with chronic obstructive pulmonary disease (COPD). Material and methods. 144 patients with COPD and 35 patients of control group were examined. The analysis of HRV and Holter monitoring were made f on 2th and 14th days. Results. Treatment with both drugs led to increase in power of low- and high frequencies and their ratio (LF/HF), decrease in rate of supraventricular and ventricular arrhythmias. Theophylline therapy raised in a number of single and pair supraventricular extrasystoles. Treatment with combination of salmeterol and fluticasone did not change a number of extrasystoles. Conclusion. Combination of salmeterol and fluticasone is more preferable as a broncholytic therapy for patients with COPD and heart rhythm disorders.

Effect of dietary hempseed intake on cardiac ischemia-reperfusion injury

Polyunsaturated fatty acids (PUFAs) have significant, cardioprotective effects against ischemia. Hempseed contains a high proportion of the PUFAs linoleic acid (LA) and alpha-linolenic acid (ALA), which may have opposing effects on postischemic heart performance. There are no reported data concerning the cardiovascular effects of dietary hempseed intake. A group of 40 male Sprague-Dawley rats were distributed evenly into four groups that were fed for 12 wk a normal rat chow supplemented with hempseed (5% and 10%), palm oil (1%), or a 10% partially delipidated hempseed that served as a control. Plasma ALA and gamma-linolenic acid levels were significantly elevated in the rats that were fed a 5% or 10% hempseed-supplemented diet, but in heart tissue only ALA levels were significantly elevated in the rats fed these diets compared with control. After the dietary interventions were completed, postischemic heart performance was evaluated by measuring developed tension, resting tension, the rates of tension development and relaxation, and the number of extrasystoles. Hearts from rats fed a hempseed-supplemented diet exhibited significantly better postischemic recovery of maximal contractile function and enhanced rates of tension development and relaxation during reperfusion than hearts from the other groups. These hearts, however, were not protected from the occurrence of extrasystoles, nor were the increases in resting tension altered during ischemia or reperfusion as a function of any dietary intervention. Our data demonstrate that dietary hempseed can provide significant cardioprotective effects during postischemic reperfusion. This appears to be due to its highly enriched PUFA content.

Ischaemic preconditioning in the rat heart: the role of G-proteins and adrenergic stimulation.

Since recent findings indicate the involvement of G-proteins in the mechanism of ischaemic preconditioning (PC), the present study was aimed to investigate the role of adrenergic mechanisms, such as G-proteins and stimulation of adrenergic receptors, in this phenomenon. For this purpose, isolated Langendorff-perfused rat hearts were subjected to regional ischaemia (30 min occlusion of LAD) followed by reperfusion. The effect of PC (a single 5 min occlusion/reperfusion before a long occlusion) on ischaemia- and reperfusion induced arrhythmias was studied in conjunction with an assessment of G-proteins in the myocardial tissue by means of Western blotting and ADP-ribosylation with bacterial toxins. To follow the link between G-proteins and adrenergic receptors, their stimulation by exogenous norepinephrine (NE) was applied to test whether it can mimic the effect of PC on arrhythmias. Thirty min ischaemia and subsequent reperfusion induced high incidence of ventricular tachycardia (VT) and fibrillation (VF). PC significantly reduced a total number of extrasystoles, incidence of VT and abolished VF. It was, however, insufficient to suppress reperfusion-induced sustained VF. Measurement of G-proteins revealed that PC led to a reduction of stimulatory Gs proteins, whereas inhibitory Gi proteins were increased. NE (50 nmol) introduced a manner of similar to PC (5 min infusion, 10 min normal reperfusion) reduced ischaemic arrhythmias in the same way, as PC. In addition, in NE-pretreated hearts reperfusion induced mostly transient VF, which was spontaneously reverted to normal sinus rhythm. A transient increase in heart rate and perfusion pressure during NE infusion completely waned before the onset of ischaemia, indicating that antiarrhythmic effect was not related to haemodynamic changes and to conditions of myocardial perfusion. antiarrhythmic effect of PC may be mediated by a stimulation of adrenergic receptors coupled to appropriate G-proteins. Consequently, the inhibition of adenylate cyclase activity and reduction in cAMP level, as well as the activation of protein kinase C may be considered as two possible pathways leading to a final response.

Nifedipine effects in severe myocardial ischaemia in the dog due to left anterior descending coronary occlusion with left circumflex coronary artery constriction.

The effects of nifedipine were studied in a model of local myocardial ischaemia, comprising anaesthetized thoracotomized dogs in which a critical constriction of the left circumflex coronary artery (LCX) was combined with sudden occlusion of the left anterior descending coronary artery (LAD). Since more than one coronary artery is involved in ischaemic heart disease, the model seems to reflect the clinical situation very closely. In this model, infusion of 1 microgram kg-1 min-1 nifedipine increased myocardial blood flow within the stenosed area served by the LCX as well as in the myocardial region supplied by the LAD, mainly in the subepicardium. Accordingly, the drug reduced ischaemic ST-segment elevation only in the epicardium. It is suggested that nifedipine directed flow to the sub-epicardium of the ischaemic area by improving the collateral circulation. This redistribution of flow resulted in a decrease in the endo/epicardial flow ratio. Nifedipine did not change the inhomogeneity of electrical activation indicating that it has no effect on the ischaemia-induced conduction delay. At the same time nifedipine was not able to reduce either the number of extrasystoles appearing in the early postocclusion and reperfusion phase or the incidence of ventricular fibrillation occurring mainly during reperfusion.

Importance of myocardial blood flow changes in the protective action of diltiazem in a new model of myocardial ischaemia.

The effect of diltiazem was studied in a new model of myocardial ischaemia in which in addition to a critical constriction of the left circumflex branch (LCX), the left anterior descending coronary artery (LAD) was suddenly occluded. This model is probably more relevant to the clinical situation in which multivessel coronary artery disease is common. In this model diltiazem exerted a beneficial effect, manifested by an increase in myocardial blood flow (MBF) within the stenosed area of the LCX; by a marked reduction of the enhanced preload (LVEDP); by a diminution of the inhomogeneity of electrical activation and by a decrease in ST-segment elevation. Diltiazem also caused a significant reduction both in the number of extrasystoles and in the incidence of ventricular fibrillation. Increased MBF within the stenosed area was associated with enhanced blood flow to the ischaemic myocardium, i.e. diltiazem directed flow to the ischaemic zone by improvement of the collateral circulation. The beneficial electrophysiological changes caused by diltiazem are probably at least partly due to the drug-induced improvement of myocardial blood supply to the ischaemic area.

Mortality Study of the Significance of Extrasystoles in an Insured Population

The prognostic significance of extrasystoles was evaluated in 712 insured persons with this finding who were followed for an average period of 18 years. At the end of the study 356 persons were alive and 125 were dead. Two hundred and thirty-one persons had terminated their policies at a prior date by maturity or discontinuance and were not followed further. Although the lack of follow-up to 1968 of this latter group imposes limitations on the results and conclusions of the study, their exclusion resulted in no significant change in the mortality ratio of the remaining group of 481 persons followed to death or the anniversary of their policies in 1968. The observed mortality ratios showed no appreciable increase in a group of 604 individuals who were considered to have a normal life expectancy except for the presence of extrasystoles at the time of evaluation for insurance. Similar normal mortality ratios were observed in subgroups with simple and complex supraventricular and ventricular extrasystoles. There was no appreciable difference in mortality when those under 40 and those 40 years of age and over at the time of discovery of extrasystoles were compared. There was no significant difference in mortality between those who responded to exercise with an increase in the number of extrasystoles and those who had no change or a decrease immediately after exercise. An increase in the number of extrasystoles per minute was associated with an increase in mortality. There was a low incidence of sudden death among those with supraventricular extrasystoles. Ventricular extrasystoles, particularly those of complex types, were associated with a high incidence of death from myocardial infarction, often of a sudden nature, particularly in persons under the age of 56 years. There were too few cases of the individual types of complex ventricular extrasystoles to determine whether this was a characteristic of the group as a whole or of one or more of its constituent types. Ventricular extrasystoles in the presence of other cardiac abnormalities and/or elevation of the blood pressure were associated with an increase in mortality. The mortality experience in such persons was distinctly higher than in those with similar degrees of substandard expected mortality whose abnormalities were not of a cardiovascular nature.