Prognosis of patients with ventricular tachycardia and ventricular fibrillation: role of the underlying etiology.

The prognosis of 149 patients with ventricular tachycardia (n = 108) or ventricular fibrillation (n = 41) was analyzed to assess the importance of the underlying etiology of the arrhythmia. Seventy-three patients (Group I) had a previous myocardial infarction and documented late sustained monomorphic ventricular tachycardia. Thirty-five (Group II) also had a previous myocardial infarction but had late ventricular fibrillation. There were 41 patients (Group III) without coronary artery disease: 9 patients with right ventricular dysplasia, 26 with idiopathic sustained ventricular tachycardia and 6 with idiopathic ventricular fibrillation. The mean follow-up period for all patients was 22 to 57 months. The total mortality rate in Group I (16%) and Group II (34%) and the arrhythmic mortality rate in Group I (5%) and Group II (11%) were significantly higher than the rates in Group III. In the latter group the total mortality rate was 4% for those with idiopathic ventricular tachycardia and 11% for those with right ventricular dysplasia, and there were no deaths due to arrhythmia (p less than 0.05). Left ventricular ejection fraction was significantly lower and left ventricular end-diastolic pressure was significantly higher in Group I and Group II than in Group III. There were nonfatal recurrences of ventricular tachycardia in 33 to 56% of patients, and the number of these episodes did not differ significantly in those with and without coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Value of the electrocardiogram in diagnosing the number of severely narrowed coronary arteries in rest angina pectoris.

The aim of this study was to assess the value of the electrocardiogram recorded during chest pain for identifying high-risk patients with 3-vessel or left main stem coronary artery disease (CAD). Therefore, the number of leads with abnormal ST segments, the amount of ST-segment deviation, and specific combinations of leads with abnormal ST segments were correlated with the number of coronary arteries with proximal narrowing of > 70%. Electrocardiograms recorded during chest pain were compared with one from a symptom-free episode. In this retrospective analysis, 113 consecutive patients were included. One-vessel CAD was present in 47 patients, 2-vessel CAD in 22, 3-vessel CAD in 24 and left main CAD in 20. Stratification was performed according to the presence of an old myocardial infarction. The number of leads with ST-segment deviations, and the amount of ST-segment deviation in the electrocardiogram obtained during chest pain at rest showed a positive correlation with the number of diseased coronary arteries. These findings were more marked when the absolute shifts from baseline were considered, because ST-segment abnormalities could be present also in the electrocardiogram obtained during the symptom-free episode. Left main and 3-vessel CAD showed a frequent combination of leads with abnormal ST segments: ST-segment depression in leads I, II and V4-V6, and ST-segment elevation in lead aVR. The negative predictive and positive accuracy of this pattern were 78 and 62%, respectively. When the total amount of ST-segment changes was > 12 mm, the positive predictive accuracy for 3-vessel or left main stem CAD increased to 86%.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of procainamide and lidocaine in terminating sustained monomorphic ventricular tachycardia.

Efficacy of procainamide and lidocaine in terminating spontaneous monomorphic ventricular tachycardia (VT) was assessed in a randomized parallel study. Patients with acute myocardial infarction and those with poor hemodynamic tolerance of VT were excluded. Procainamide 10 mg/kg was given intravenously with an injection speed of 100 mg/min, and lidocaine was administered at an intravenous dose of 1.5 mg/kg in 2 minutes. Fourteen patients were randomized to lidocaine and 15 to procainamide. Termination occurred in 3 of 14 patients after lidocaine and in 12 of 15 patients after procainamide (p <0.01). Procainamide stopped 8 of 11 VTs not responding to lidocaine, and lidocaine stopped 1 of 1 not responding to procainamde. Of a total of 41 VT episodes, 4 of 15 responded to lidocaine and 20 of 26 to procainamide (p <0.01). Because of VT recurrences, 16 patients could be studied repeatedly with drugs given in the reversed order. This resulted in a total of 55 trials of 79 drug injections. Lidocaine terminated 6 of 31 VTs and procainamide 38 of 48 (p <0.001). The protocol was stopped in 4 cases because of adverse effects. A comparison of the QRS width and QT interval before and at the end of the injection revealed significant lengthening of these values after procainamide but no change after lidocaine. In conclusion, procainamide is superior to lidocaine in terminating spontaneously occurring monomorphic VT.

Evaluation of new self-learning techniques for the generation of criteria for differentiation of wide-QRS tachycardia in supraventricular tachycardia and ventricular tachycardia.

This study presents a comparison of three different methods for differentiating between supraventricular and ventricular tachycardias with wide-QRS complex. One set of criteria, derived using classical statistical techniques, was compared with two new self-learning computer techniques: the artificial neural networks and the induction algorithm approach. By analyzing the results obtained in an independent test set, using these new techniques, the criteria defined by the classical method could be improved.

The value of an expert system in performing clinical drug trials.

An expert system has been designed to assist the cardiologist in determining whether patients can be included in clinical trials. This system contains knowledge on inclusion and exclusion criteria for six drug trials, and has been validated in 100 randomly selected patients. In 97 cases, the expert system and the cardiologist made an identical classification; in the remaining three cases, the patient was incorrectly classified by the physician. The system will also optimize the order in which questions are asked in order to minimize the time required to decide on inclusion or exclusion.

Artificial neural networks and ECG interpretation. Use and abuse.

The computerized interpretation of the resting electrocardiogram has reached a steady-state phase: an equilibrium between sensitivity and specificity has been reached. New computer techniques, such as expert systems and artificial neural network technology, have been proposed or are currently under evaluation. Although neural network techniques are based on complex mathematical theories and their application is full of pitfalls, progress has been made in a number of subdomains, like signal filtering, electrocardiographic classification, and compression of stress electrocardiograms. Presently, the hesitating acceptance by the human user forms one of the obstacles that needs to be overcome by convincing, well-performed studies.

Development of ECG criteria to diagnose the number of narrowed coronary arteries in rest angina using new self-learning techniques.

Recently, an evaluation of the value of the resulting electrocardiogram recorded during chest pain for identifying high-risk patients with three-vessel or left main stem coronary artery disease has resulted in the definition of one characteristic pattern: ST-segment depression in leads I, II, and V4-V6 and elevation in lead aVR. This study evaluated the generation of such criteria using two self-learning techniques: neural networks and induction algorithms. In 113 patients, five variables, including the amount of ST elevation, the number of leads with abnormal ST-segments, and this above-mentioned characteristic sign, were correlated with the number of narrowed vessels. All patients were randomly subdivided into a training (n = 63) and test set (n = 50), stratified for both this characteristic sign and for the vessel involved. Using the learning set, the neural network and the induction algorithm were trained separately to identify (1) pure left main stem disease and (2) three-vessel disease and left main stem disease. The neural network was trained for 1,000 runs. The induction algorithm was trained, allowing all variables to be used in any order. The experiments were repeated after adding weight factors to promote the recognition of the more severe cases. Subsequently, the ST elevation in all 12 leads was added to the training and test sets, once with and once without the polarity of the ST deviation. Altogether, 18 different combinations were evaluated. Basically, the neural network and the induction algorithm approach misclassified the same cases in corresponding test combinations.(ABSTRACT TRUNCATED AT 250 WORDS)

The value of the clinical history to assess prognosis of patients with ventricular tachycardia or ventricular fibrillation after myocardial infarction.

Multivariate analysis using 70 variables in 200 patients who suffered from ventricular tachycardia or ventricular fibrillation after myocardial infarction detected eleven variables that were associated with an increased risk of sudden arrhythmic death and cardiac death during a mean follow-up period of 2 years. Four of the 11 variables came from the patient's clinical history: (1) cardiac arrest at the time of the first spontaneous episode of arrhythmia, (2) New York Heart Association functional class for dyspnoea = III, (3) ventricular tachycardia or ventricular fibrillation occurring early (after 3 days and within 2 months) after myocardial infarction, (4) multiple myocardial infarctions before the first episode of ventricular tachyarrhythmia. Total mortality, incidence of sudden arrhythmic death and of non-sudden cardiac death increased with an increasing number (zero, one, two, three, four) of variables seen in individual patients. Patients with zero or one variable had an incidence of sudden death of 2.8% and a 4.2% incidence of non-sudden cardiac death at 26 months, while patients with more than two variables had a 13.5% and a 20.3% incidence respectively of sudden and non-sudden cardiac death. The strongest predictor of sudden death was the occurrence of cardiac arrest during the first spontaneous episode of ventricular arrhythmia. The strongest predictor of non-sudden cardiac death was the New York Heart Association functional class. The use of the four variables to stratify risk revealed seven subgroups of patients with incidences of sudden death ranging from 0 to 28%.(ABSTRACT TRUNCATED AT 250 WORDS)

Cost-benefit analysis of medical vs surgical treatment of symptomatic patients with accessory atrioventricular pathways.

Surgical treatment of patients with an accessory atrioventricular pathway leading to symptomatic arrhythmias provides effective control. However, surgical treatment is usually considered only when medical treatment fails. To assess the cost-benefit ratio of medical vs surgical treatment 77 patients treated with antiarrhythmic drugs were compared with 50 patients treated surgically. Cost was calculated by considering current costs for drugs, surgery and pacemakers, electrophysiological investigations, outpatient clinic controls, and costs of readmissions because of tachycardia. Mean cost per treated patient and mean cost per successfully treated patient (total cost divided by the number of patient not requiring readmission during follow-up) was respectively 4242 and 6949 US dollars after 56 months for the medically treated group and 10800 and 11250 US dollars for the surgically treated group. A projection of costs demonstrated that costs of medical treatment was the same as costs of surgical treatment after 12.5 years of treatment but a higher number of medically treated patients remain symptomatic. We conclude that surgical treatment of symptomatic patients with accessory pathways has a better cost-benefit ratio than medical treatment and should be considered earlier without waiting for failure for medical treatment.

An artificial neural network to localize atrioventricular accessory pathways in patients suffering from the Wolff-Parkinson-White syndrome.

UNLABELLED: The electrocardiographic localization of atrioventricular accessory pathways has been extensively described in the literature by a number of well-known electrophysiologists and surgeons. These descriptions, often represented as decision trees, are useful, but do not apply in all cases. To formalize the process of determining the proper localization, this expert human knowledge could be represented in an expert system. But since reasoning is partly based on the use of heuristic knowledge, and are often not represented in the written description of the human expert, the results will be suboptimal. On the other hand, by using a self-learning neural network approach, the causal relations between input (polarity of the delta waves) and output (the correct localization) do not have to be defined by the expert. It is derived by the neural network, by analyzing a learning set of cases consisting of the ECG plus the corresponding correct localization. In our set of 60 cases, 2 hours of training were required to learn how to localize all cases correctly. From a control set of 25 cases, 23 were interpreted by the system satisfactorily. CONCLUSION: the neural network approach can be useful in situations where causal relations between the electrocardiogram and underlying mechanism are partly undefined.