An unusual cause of giant T waves.

In the acute care setting, the two most common causes of giant upright T waves include hyperkalemia and the very early phase of acute myocardial infarction (MI). The former is characterized by narrow based and peaked T waves. The giant T waves of early MI, also called "hyperacute T waves," are usually more broad-based. The general recommendation is to consider hyperacute T waves a form of occlusion MI, and to proceed with emergent cardiac catheterization and revascularization. In this report, we present the case of a young man with cocaine toxicity and status epilepticus where the initial electrocardiogram (ECG) demonstrated giant T waves. Both hyperkalemia and coronary occlusion were ruled out. Within a few hours, the ECG spontaneously normalized. Review of the literature revealed that although uncommon, acute cerebral events including seizures can cause transient giant T waves. When giant T waves are noted in association with a cerebral event, emergent cardiac catheterization may not be warranted.

What are those intermittent "S" waves?

A 69-year-old woman had three syncopal events while flying on an airplane. She was found to be profoundly bradycardic. Two 12­lead electrocardiograms (ECGs) showed ventricular rates in the thirties. In one, the QRS complexes were narrow. In the second ECG, there were wide negative deflections following the QRS complexes. Analysis of telemetry recordings revealed the underlying mechanism and helped establish appropriate programing of an implanted pacemaker.

Common ECG interpretation software mistakes Part II: Computer errors that hide diagnostic clues.

Electrocardiogram (ECG) interpretation software mistakes can lead to incorrect diagnoses and inappropriate treatments. Occasionally, however, repetitive and consistent computer errors may hide important clues for correct diagnoses that otherwise could have been missed. We present a collection of a few common and clinically important such peculiarities, and provide tools on how to prove or disprove the suspected diagnosis. In addition to the illustrations in print, an online supplement (OS) shows more examples of the discussed phenomena. In each ECG, the original computer interpretations were enlarged for legibility.

Common ECG interpretation software mistakes Part III: Computer errors that should never be missed.

Electrocardiogram interpretation software mistakes can lead to incorrect diagnoses and inappropriate treatments. Occasionally, the consequences of not recognizing such mistakes are disastrous. This final chapter on software mistakes describes three relatively common computer errors that should never be missed because not recognizing them can result in stroke, cardiac arrest, and even death. In each of the scenarios covered, we describe the clinical background, and provide simple recommendations on how such mistakes can be easily identified and corrected.

Common ECG interpretation software mistakes. Part I: False reporting of myocardial infarction.

The purpose of computerized analysis of electrocardiograms (ECGs) is to provide rapid interpretation in places where ECG experts are not available, and to save physician time for all providers. For the most part, contemporary interpretation algorithms perform remarkably well and offer correct diagnoses of common ECG abnormalities. Diagnostic accuracy for myocardial ischemia and infarction is reasonably good but with these conditions, false positive and false negative readings can be disastrous. It is essential, therefore, that computerized statements be over-read by trained physicians. A three-part mini-series is intended to provide assistance to quickly recognize and correct common interpretation software mistakes. This first chapter presents interpretation errors that falsely indicate myocardial infarction.

Precordial ST-segment continuum: A variant of the de Winter sign.

The vast majority of patients with acute occlusion of the proximal left anterior descending coronary artery (LAD) suffer frank ST-elevation myocardial infarction (STEMI). In contrast, a small but not insignificant minority presents with an electrocardiographic (ECG) pattern termed the "de Winter sign." The de Winter sign is characterized by upsloping ST depression followed by tall and peaked T waves in the precordial leads. The purpose of this report is to present two cases of acute obstruction of a large wrap-around LAD where the ECGs simultaneously displayed diagnostic criteria both for STEMI and the de Winter sign. We provide possible explanations for this hitherto undescribed phenomenon.

A new electrocardiographic concept: V1-V2-V3 are not only horizontal, but also frontal plane leads.

According to conventional teaching, the limb leads in the electrocardiogram (ECG) represent the frontal plane electrical vectors of the heart, whereas the chest leads signify the horizontal plane. The anterior chest leads V1-V2-V3, however, also have strong frontal plane representation which can result in morphological similarities in these leads to the augmented unipolar leads of the Einthoven triangle. This review highlights the significance of recognizing V1-V2-V3 as not only horizontal, but also as frontal plane leads. Appreciation of this phenomenon helps elucidate a colorful variety of clinically important but seemingly bizarre ECG manifestations that could not be explained otherwise.

Electrocardiographic artifact.

Electrocardiographic (ECG) artifact, a common nuisance, has a wide range of manifestations with varying clinical significance. Beyond loose leads, motion artifacts and broken wires, artifact can also be caused by external and implanted devices as well as by physiologic signals. ECG artifact can mimic a variety of serious clinical conditions and arrhythmias such as acute myocardial infarction and ventricular tachycardia. The purpose of this review is to provide a structured approach to the recognition of the different forms of ECG artifact and to offer simple and practical steps to avoid misdiagnoses caused by artifact. Special attention is given to artifact whose presence can actually aid in the diagnosis of important and sometimes critical clinical conditions.

Trouble begets trouble; overcounting the heart rate by the interpretation software results in overestimation of the QTc.

A man in his 70s was taking a medication that required routine electrocardiographic (ECG) monitoring for possible QT prolongation. On one of these occasions, four consecutive ECGs were recorded within 1 min. Unexpectedly, the rate-corrected QT intervals (QTc) reported by the interpretation software showed marked fluctuation ranging from 426 ms to 498 ms. Was there a rational explanation for the widely different QTc measurements? Was it necessary to hold the culprit medication?

Regular ventricular rate and "reverse bigeminy" in 3:2 Wenckebach periodicity.

One of the more common causes of bigeminy at the ventricular level is type 1 second-degree atrioventricular (AV) block with 3:2 conduction ratio. In 3:2 Wenckebach, the shorter cycles reflect the consecutively conducted impulses and the longer cycles coincide with the blocked P waves. Theoretically, however, depending on the degree of conduction delay between the first and second transmitted impulses, other types of spacing of the QRS complexes may become possible. In this retrospective study of 180 patients who underwent electrophysiologic studies for symptomatic arrhythmias, atrial pacing-induced 3:2 Wenckebach periodicity resulted in a regular ventricular rate and/or in "reverse bigeminy" in 16 cases (8.9%). Reverse bigeminy was characterized by the shorter R-R intervals including both the blocked P waves and the first conducted beats of the subsequent cycles, and the longer R-R intervals coinciding with the second conducted beats during 3:2 Wenckebach. In 14 cases, regular ventricular rate and reverse bigeminy was triggered by marked conduction delay in the AV node and in 2 cases, the conduction delay was in the His-Purkinje system. Reverse bigeminy appeared to be related to dual AV nodal physiology in 8 patients. In 2 cases, sophisticated maneuvers such as termination of atrial pacing at critical intervals during the AV Wenckebach were required to expose the true conduction pattern. This study demonstrates that during rapid atrial rhythms, one cannot always be sure which P wave is responsible for which QRS complex. Rarely, extreme conduction delays can result in P waves conducting across the subsequent ventricular beats and be responsible not for the first, but for the following QRS complexes.

Real-time validation of the Sgarbossa and modified Sgarbossa criteria in intermittent left bundle branch block.

The modified Sgarbossa criteria have been established to aid in the diagnosis of ST-elevation myocardial infarction in patients with left bundle branch block. Thus far, the sensitivities and specificities of the Sgarbossa signs have only been evaluated retrospectively in cohorts of patients with and without occlusive myocardial infarctions. These statistical analyses were based on correlating ST abnormalities with serum markers of myocardial injury and/or results of emergent cardiac catheterization. We present a patient with acute cardiovascular emergency where electrocardiograms revealed intermittent left bundle branch block. In serial ECGs, highly dynamic ST abnormalities on the narrow QRS beats were associated with similarly dynamic ST changes in the left bundle branch block beats. Our findings provided direct and real-time confirmation of the usefulness of the Sgarbossa and the modified Sgarbossa criteria in the diagnosis of acute ST elevation in patients with left bundle branch block.

Initial evaluation and management of wide-complex tachycardia: A simplified and practical approach.

The evaluation and treatment of wide QRS-complex tachycardia remains a challenge, and mismanagement is quite common. Diagnostic aids such as wide-complex tachycardia algorithms perform poorly in the real-life setting. The purpose of this review is to offer a simple clinical-electrocardiographic approach for the initial evaluation and management of the adult patient with stable wide-complex tachycardia that does not require recollection of complex guidelines or algorithms.

Spiked helmet pattern ST elevation in subarachnoid hemorrhage.

Subarachnoid hemorrhage (SAH) is occasionally associated with the electrocardiographic (ECG) pattern of ST-segment elevation myocardial infarction (STEMI). Missing the true clinical diagnosis can result in inappropriate and harmful interventions. We report the case of a 40-year-old female who was found down. The ECG was diagnostic for acute lateral STEMI. Further analysis of the ECG showed marked prolongation of the QT interval and the "spiked helmet sign" (SHS). The patient was ruled out for myocardial infarction and a head CT demonstrated a massive SAH with acute hemorrhage into the ventricles. Review of the literature and of our own ECG files revealed additional cases where severe acute central nervous system (CNS) conditions were associated with the SHS.

Evolution of our understanding of the aVR sign.

In patients presenting with signs and symptoms of an acute coronary syndrome (ACS) the combination of multilead ST depression and ST elevation in lead aVR, the electrocardiographic "aVR sign," has been associated with severe left main coronary artery stenosis or diffuse coronary artery disease and a high risk of death. Recent guidelines even suggest that the aVR sign may represent an ST-elevation myocardial infarction (STEMI) equivalent and therefore, an indication for emergent cardiac catheterization and reperfusion. The specificity of the aVR sign for left main disease, however, has been questioned as multiple additional high-risk clinical conditions have also been shown to be associated with the aVR sign. The purpose of this review is to provide a historic background of the aVR sign and to summarize the evolution of our understanding of this important electrocardiographic (ECG) phenomenon. Using two illustrative cases, we wish to highlight the significant risks associated both with under-appreciation of the aVR sign as well as hastily overreacting to the aVR sign.

Electrocardiographic manifestations of severe hyperkalemia.

Severe hyperkalemia is a hazardous condition that warrants urgent intervention. In critically ill patients, the electrocardiogram (ECG) can be the most immediately available diagnostic tool in identifying patients with potentially lethal hyperkalemia. Peaking of the T waves, the most widely appreciated ECG sign, is actually rarely a manifestation of life-threatening hyperkalemia. In this review, we provide several clinical-electrocardiographic manifestations that can help identify those patients with hyperkalemia who require prompt intervention.