Electrocardiographic Changes in Spontaneous Left Pneumothorax

ABSTRACT. Keller N, Szaff M, Sykulski R (Department of Internal Medicine, Sundby Hospital, Copenhagen, Denmark). Electrocardiographic changes in spontaneous left pneumothorax. Acta Med Scand 1987; 221:499–501. A 25-year-old man was admitted with severe chest pain and an electrocardiogram suggestive of anterior myocardial infarction. Echocardiogram was normal, but chest X-ray showed left-sided pneumothorax. The electrocardiogram showed increasing R-wave amplitude in the days after correction of pneumothorax. Taken in the supine position the electrocardiogram can be misleading in case of pneumothorax or mediastinal emphysema, but the electrocardiogram should be normal if taken in the erect position.     

Mode of Onset of Malignant Ventricular Arrhythmias in Idiopathic Ventricular Fibrillation

Mode of Onset of Idiopathic VF. Introduction : The mode of onset of malignant ventricular arrhythmias (ventricular tachycardia [VT] or ventricular fibrillation [VF] has been well described in patients with organic heart disease and in patients with the long QT syndromes. Less is known about the mode of onset of VF in patients with out-of-hospital VF who have no evidence of organic heart disease or identifiable etiology.
Methods and Results : We reviewed the ECGs of all our patients with Idiopathic VF. Documentation of the onset of spontaneous arrhythmias was available for 22 VK episodes in 9 patients (6 men and 3 women; age 41 ± 16 years). In all instances, spontaneous VF followed a rapid polymorphic VT, which was initiated by premature ventricular complexes (PVCs) with very short coupling intervals. The PVC initiating VF had a coupling interval of 302 ± 52 msec and a prematurity index of 0.4 ± 0.07. These PVCs occurred within 40 msec of the peak of the preceding T wave. Pause-dependent arrhythmias were never observed.
Concltision : Cardiac arrest among patients with idiopathic VF has a very distinctive mode of onset. Documentation of a polymorphic VT that is not pause dependent is of diagnostic value.     

Noninvasive Recording of His-Purkinje System (HPS) Activity in Man on Beat-To-Beat Basis

Since 1969 His bundle electrography has been used for diagnosis and for the study of cardiac electrophysiology. This method has employed the catheterization technique and has allowed the continuous recording of electrical activity of the specialized cardiac conduction system in every beat. Such investigation, because of its invasive nature, cannot be considered a routine test; it requires expensive instrumentation, it has physiological and technical limitations that include discomfort, a slight morbidity risk and a rather limited recorded area within the heart. In 1973 a method was developed for a noninvasive recording of the electrical activity within the P-R segment of the electrocardiogram measured from the body surface. This method which employs the signal averaging technique delivers even less medical information than intracardiac measurement. The shortcomings of this averaging method include inability to detect beat-to-beat changes in the true signal. Such a method is not useful in transient arrhythmia detection and a "short acting" drug influence examination. The technical approach to the beat-to-beat noninvasive recording of the HPS activation signal as measured from the body surface has been proposed. Using a specially positioned electrode system, a low noise multiple parallel input amplifier and a computer for sampling, processing and plotting of the measured signal, we have obtained an output curve corresponding to the continuous beat-to-beat HPS activity.     

Adaptive Filtering in Exercise High Resolution ECG as Applied to the Hypertrophic Cardiomyopathy

KEPSKI, R., et al. : Adaptive Filtering in Exercise High Resolution ECG as Applied to the Hypertrophic Cardiomyopathy. The application of adaptive filtering to ECG signals has been investigated for many years. This study shows that the exercise high resolution ECG (HRECG) can also be processed successfully in a similar way. Two groups were included consisting of 20 healthy individuals and 24 patients with hypertrophic cardiomyopathy (HCM) . The HRECG parameters for both groups were similar (  QRSdur: 107 ± 7 vs 114 ± 18 ms NS, LAS: 25 ± 8 vs 22 ± 6 ms NS  ). In the first step, the HRECG signal was acquired at rest to obtain the averaged reference pattern. The next step was associated with peak exercise in which one could calculate short duration averaging (∼ 30 beats) or apply adaptive filtering in which the exercise component (EC) was extracted. Exercise was performed in the supine position on a bicycle ergometer. The load of 50 W was incremented by 50-W steps in 3-minute intervals and the test was ended by fatigue. Signals were recorded in X, Y, and Z bipolar leads with a 20-Hz high pass filter. The short time average QRS duration mostly was abbreviated in normal individuals in contrast to HCM patients in which ventricular activity prolonged with sensitivity, specificity, and negative and positive predictive values: 79%, 65%, 73%, and 72%, respectively. The adaptive recurrent filtration (ARF) after cutoff of the EC at the level of 70 ms (this level is the EC mean value of both groups) showed the following statistics: 63%, 90%, 88%, and 90%. The Student's t-test as applied to the duration of EC allowed a statistically significant difference between normals and HCM patients (  66 ± 4 vs 71 ± 6 ms, P < 0.0052  ) and between HCM patients with and without ventricular tachyarrhythmia and DS (  74 ± 6 vs 69 ± 6 ms, P < 0.046  ).     

Pyramid Electrode Location in a Cardiac Micropotential Study

There are several electrode systems dealing with low noise, body surface, and ECG recordings that have been suggested by various investigators. In the last few years, the most developed system for late potential detection has been related to the uncorrected Frank XYZ leads. However, for His bundle detection many different electrode networks have been used. A pyramid-type electrode system has been used previously for His-Purkinje signal measurement and, with some modifications, for late ventricular activity recordings. This pyramid-type system was used to evaluate 300 adult patients with coronary heart disease (CHD) or cardiomyopathy. In the proposed system, electrodes are located near the myocardium with their configuration consisting of three electrode pairs forming a pyramidal shape. Each electrode can also play the role of the top of the pyramid, with all measurement directions converging to a point. By changing the pyramidal top, signals can be detected in various chosen measurement directions. The pyramid system provides spatial averaging facility, allowing the whole measuring system (consisting of low noise multi-input amplifiers) to detect signals in the range of 1 microVp-p on a beat-to-beat basis. In the majority of cases in hospital environments, however, a number of digital averaging cycles is still necessary. Using this system, late potentials (LP) were found in 29% of the patients without myocardial infarction (MI) and in 86% of cases with remote MI and sustained ventricular tachycardia (VT) and/or ventricular fibrillation (VF). Waveforms suspected to be of His-Purkinje System (HPS) origin were detected in 71% of subjects with normal or prolonged P-R segment.     

Diabetes and Multiple Stents Independently Double the Risk of Short-term Revascularization

Several studies show worse outcome for diabetic patients after percutaneous transluminal coronary angioplasty (PTCA). There are relatively few studies evaluating outcome in the modern era of coronary stenting. We compared the incidence of death, myocardial infarction (MI), and repeat target lesion revascularization (RTLR) by PTCA or coronary artery bypass grafting (CABG) over a 6-month follow-up in 110 diabetic and 400 nondiabetic patients receiving Palmaz-Schatz stents. All patients received aspirin/ticlopidine and stents were deployed using high-pressure inflations. Seventy-five (68.2%) diabetic patients and 272 (68%) nondiabetic patients had single stents, while 35 (31.8%) diabetic and 128 (32%) nondiabetic patients had multiple stents (≥ 2stents in the same vessel). The success rate and acute major complications were not significantly different between diabetic and nondiabetic patients. There was also no significant difference in death, MI, and repeat PTCA between these two groups. Diabetic patients underwent CABG more frequently than nondiabetic patients (12.7% vs 3.2%, respectively, P =0.001) and diabetic patients also had RTLR more frequently than nondiabetic patients (25.5% vs 12.8%, respectively, P = 0.002) during 6-month follow-up. Multivariate analysis showed that diabetes and multiple stents independently contributed to the 6-month RTLR rate. Coronary stenting in diabetic patients can be carried out with a high success rate and low incidence of acute major complications. The presence of diabetes mellitus and multiple stent placement significantly increase the incidence of repeat target lesion revascularization.     

Is the Outcome of Coronary Stenting Worse in Elderly Patients?

Initial reports of percutaneous transluminal coronary angioplasty (PTCA) in the elderly (≥: 75 years) showed a significantly lower primary success rate, higher in-hospital mortality, and a higher risk of emergency or elective coronary artery bypass graft (CABG) compared to younger patients. There are few data concerning acute outcomes and clinical follow-up after the use of coronary stenting in the elderly compared to < the 75-year-old age group. We evaluated 82 elderly patients and 280 younger patients who received Palmaz-Schatz stents during 1995, at a time when high pressure deployment and antiplatelet therapy was routinely used. The success rate and acute major complications were not significantly different between the elderly and younger patients. Clinical events (death, myocardial infarction [MI], repeat PTCA, or CABG) during 6-month follow-up were also not significantly different. Coronary stenting in the elderly can be carried out with a high success rate and low incidence of acute major complications. Thus, short-term clinical outcomes in elderly patients appear similar to results obtained in younger patients.