Q-wave versus non-Q wave myocardial infarction: a meaningless distinction.

The whole subject can thus be summed up in two statements. 1. Every appropriately designed study comparing first Q and NQMI's has found no difference in post-MI course of the two categories and no foundation for the common notion that the NQMI is a uniquely "unstable" entity, to be classed with unstable angina in terms of prognosis and management. Nine such studies have been published. On the other hand, all studies alleging the "unstable" character of the NQMI have been invalidated by major flaws, chief among them the comparison of undifferentiated mixtures of first and subsequent infarcts with widely differing mortality and morbidity. This confusion is further compounded by the fact that subsequent infarcts generate Qwaves less than half as often as first infarcts. 2. All current studies indicate that there is no benefit to an invasive as compared with a conservative protocol for management of NQMI. Since the characterization of an infarct as "non-Q' conveys no therapeutic implications, the classification becomes irrelevant and should be discarded. Two quotations sum the whole matter succinctly. Moss (63) commented that "The Q-wave versus non-Q-wave categorization does not provide sufficient sensitivity, specificity, or predictive accuracy about the subsequent clinical course of patients with a first myocardial infarction to use it as reliable data in the clinical decision-making process." Surawicz (64) put the matter even more concisely: ". . . a non-Qwave MI is not a unique entity: rather it is a smaller and less extensive MI." In a word, the magnitude of a myocardial infarction should be judged on anatomical and functional considerations rather than on the designation of Qwave versus non-Qwave infarction.

Value of leads V7-V9 in diagnosing posterior wall acute myocardial infarction and other causes of tall R waves in V1-V2.

Left posterolateral chest leads (V7, V8, V9) helped distinguish the multiple causes of tall R waves in V1 and/or V2, diagnosed true posterior myocardial infarction when standard leads did not, and identified the presence or absence of posterior injury in patients with inferior infarction.

Ventricular tachycardia, diagnosis and misdiagnosis: a case report.

We report a patient who, despite significant cardiac disease and inappropriate therapy, endured continuous undiagnosed ventricular tachycardia (VT) for 5 days without hemodynamic deterioration. The two main reasons for the frequently missed diagnosis of VT are (1) the mistaken belief that VT cannot be well tolerated, and (2) ignorance of the many helpful electrocardiographic clues. Six precepts for avoiding misdiagnosis are enunciated.

Prehospital actions by health-care providers and physicians.

Extensive worldwide experience and literature exist on the benefits of early intervention in patients with an acute myocardial infarction. To make these benefits available to as much of the population as possible a number of goals have to be accomplished. Patients and bystanders must be taught to recognize the significance of symptoms and call immediately for assistance. Local emergency medical service has to dispatch appropriate personnel and equipment to the scene expeditiously. Transport without unacceptable delays must occur to appropriate facilities along with rapid initiation of treatment. A program to achieve these goals would be expected to substantially reduce morbidity and mortality. Attention is directed to prehospital actions by health-care providers including dispatch of personnel and equipment to the scene, stabilization and treatment in the field, and triage and transport of the patient to the most appropriate medical facility.

Differential diagnosis of supraventricular and ventricular tachycardia.

Few if any medical decisions are of more urgent importance than the accurate discrimination between ventricular tachycardia and supraventricular tachycardia with ventricular aberration, and probably no common diagnosis is more often missed. Yet the distinction can often be readily made with a knowledge of the several clues here described. These include QRS morphology, polarity and width; and clinical or electrocardiographic evidence of independent atrial activity. Knowledge and application of these serviceable clues should enable the clinician to establish a correct diagnosis in 90% of wide-QRS tachycardias without resorting to invasive studies.

Ventricular tachycardia: noninvasive differentiation from supraventricular tachycardia.

The paramount importance of differentiating the wide-QRS tachycardias is stressed, and the alarming frequency of errors made by practicing physicians and cardiovascular nurses is documented. The most common causes of error are outlined, of which the most important is ignorance of diagnostically helpful QRS morphology in the electrocardiogram (EKG). The QRS contours and polarity that are useful in diagnosis are described in detail and illustrated. Finally, certain compromises in electrode placement that may be necessary in the operating room are suggested.

Why are so many critical care nurses unable to recognize ventricular tachycardia in the 12-lead electrocardiogram?

We submitted the 12-lead electrocardiogram of an easily recognized ventricular tachycardia to more than 2500 critical care nurses for diagnosis. Seventy-eight percent of these failed to diagnose ventricular tachycardia, opting for supraventricular tachycardia with ventricular aberration. It was clear that only 0.5% of 2500 experienced nurses knew the three clues available for diagnosing ventricular tachycardia.

Potential benefits of a computer ECG interpretation system for primary care physicians in a community hospital.

One hundred fifteen ECGs from a hospital service were interpreted by 2 primary care physicians and 2 expert electrocardiographers. When their interpretations were compared with one another and with the Marquette MAC II ECG Interpretation Program, there was great variability. Computer ECG interpretations appeared to benefit primary care physicians most by providing a backup opinion. This second opinion was also of use to expert electrocardiographers. Additional long-term benefits that may be derived from computer systems include improvement of physician interpretation ability, reduction in interpretation time, and standardization of electrocardiographic nomenclature and criteria.

Left bundle branch block with right axis deviation: a marker of congestive cardiomyopathy.

Three patients with primary congestive cardiomyopathy (COCM), complete left bundle branch block (LBBB) and right axis deviation in the standard leads are described. Review of 50 additional patients from the literature since 1950 indicates that the uncommon combination of LBBB and RAD is a marker of severe myocardial disease, especially COCM. The mechanism of production of this electrocardiographic pattern appears to be diffuse conduction system involvement in advanced myocardial disease.

Indications for pacing in the treatment of bradyarrhythmias. Report of an independent study group.

Indications for permanent pacing in the bradyarrhythmias are summarized. In the absence of symptoms, pacing is justified only when Mobitz type II block or complete atrioventricular (AV) block is localized in the bundle-branch system. All other abnormalities of impulse generation or conduction (incomplete AV block of any type, atrial fibrillation with slow ventricular response, or sinus node dysfunction) must be shown to be stable and intrinsic and to cause CNS symptoms or hemodynamic compromise to justify pacing. Isolated intra-Hisian abnormality without failure of AV conduction is benign. Measurement of HV interval does not contribute significant information. Correlation of carotid sinus sensitivity with carotid sinus syncope is poor (5%). Bradyarrhythmia produced by minimal effective doses of an essential drug is a rare indication for pacing and requires special documentation. Inadequate indications, sources of error, and misconceptions are discussed. Generally, it is important to exclude drug effect, transient clinical states, and correctable systemic disease as causes of the abnormality before making a conclusion about pacing.

Improved ECG monitoring during cardiac catheterization using radiotransparent electrodes and chest leads.

Improved electrocardiographic monitoring during cardiac catheterization and angiography is achieved when precordial leads can be used and base line wander and muscle artifact are eliminated or reduced. This can be realized with the use of radiotransparent gold electrodes applied to the chest in C1 and C6 locations. Radiotransparency of the electrodes enables them to be situated on the chest wall throughout the diagnostic procedures without interfering with the radiographic image. The electrical stability of gold helps to eliminate base line drift; the precordial location is less subject to movement and muscle artifact and less restricting for the patient. The electrodes are made from gold film vacuum-deposited on 2 mil mylar with a copper wire five-thousandths of an inch in diameter mounted between two layers of plastic tape. The benefits of this arrangement have been observed in a series of ten patients undergoing cardiac catheterization.

Atrioventricular block: incidence in acute myocardial infarction and determinants of its "degrees".

There are several reasons why an atrial impulse may not reach the ventricles; only one of them is A-V block. Widespread failure to appreciate this simple truth is mainly responsible for the persisting confusion in the diagnosis and treatment of heart block. We have defined and illustrated the various "degrees" of A-V block; applied our definitions in analyzing the examples of block encountered among 300 consecutive incidents of acute myocardial infarction; listed, discussed, and illustrated the several factors that determine conduction ratios and, therefore, the "degree" of block; and used references and illustrations from widely accepted authorities to substantiate our claim that diagnostic and, therefore, therapeutic chaos reigns.

Electrocardiographic changes in precordial leads during selective coronary angiography.

Precordial electrocardiographic leads V1, V2, V5, V6, and limb leads I and II were recorded simultaneously utilizing radio transparent electrodes and wire leads during coronary angiography in 35 patients with obstructive coronary disease and in 17 subjects with normal coronary angiograms. The pattern of electrocardiographic changes produced by injection of contrast material into either the right or left coronary artery was similar in both groups of patients. During injections into the left coronary artery a leftward shift of the QRS occurred. Injections into the right coronary artery also produced a leftward shift of depolarization forces but, in addition, the QRS became inferiorly directed more consistently than during left coronary injections. The changes produced by angiography in the pattern of repolarization consisted of a marked increase in T wave amplitude and the transient appearance of large U waves. The changes in T waves were consistently opposite in direction to those of the QRS. The polarity of the U wave coincided with that of the T wave in the majority of cases. No consistent differences in the pattern of electrocardiographic changes were observed in subjects with a dominant right coronary artery from those with a dominant left system nor in subjects with normal coronaries from those with occlusive coronary disease.