Prehospital ECG with ST-depression and T-wave inversion are associated with new onset heart failure in individuals transported by ambulance for suspected acute coronary syndrome.

Background: Prehospital electrocardiogram(s) (ECG) can improve early detection of acute coronary syndrome (ST-segment elevation myocardial infarction [STEMI], non-STEMI, and unstable angina) and inform prehospital activation of cardiac catheterization lab; thus, reducing total ischemic time and improving patient outcomes. Less is known, however, about the association of prehospital ECG ischemic findings and long term adverse clinical events. With this in mind, this study was designed to examine the: 1) frequency of prehospital ECGs for acute myocardial ischemia (ST-elevation, ST-depression, and/or T-wave inversion); and, 2) whether any of these specific ECG features are associated with adverse clinical events within 30 day of initial presentation to the emergency department (ED).

Effects of Verapamil and Pinacidil on Extracellular K, pH, and the Incidence of Ventricular Fibrillation during 60 Minutes of Ischemia.

Ca-channel antagonist verapamil and ATP-sensitive K-channel opener pinacidil are known to decrease the rise in extracellular K ([K]) level and pH (pH) that occurs during reversible acute myocardial ischemia and to lessen the accompanying activation delay. Verapamil is also known to decrease the incidence of ventricular tachycardia (VT)/fibrillation (VF) during acute myocardial ischemia; however, the effects of ATP-sensitive K-channel opener on the incidence of VT/VF are controversial. We studied, in an in vivo pig model, the effects of verapamil and pinacidil on the changes in [K] level and pH, local activation, and the incidence of VT/VF during 60 minutes of ischemia.

Effects of Propranolol and Verapamil on Changes in TQ and ST Segment Potentials During Graded Coronary Flow Reduction in a Porcine Myocardial Ischemia Model.

Acute myocardial ischemia causes TQ depression and ST elevation. However, the effects of cardioprotective drugs such as β-blockers and Ca-antagonists on the extent of TQ depression, ST elevation, and myocardial ischemic injury are not fully understood.We created a carotid-coronary shunt in 30 pigs, and extracellular K ([K]), TQ, and ST segments were recorded simultaneously with K-selective plunge electrodes placed in the left anterior descending artery (LAD) distribution during graded LAD flow reduction before and after administration of propranolol or verapamil.

Initial and Secondary ST-T Alternans During Acute Myocardial Ischemia in the In-Situ Pig Heart.

The factors responsible for the ST-T wave alternans (STTA) and associated arrhythmias during acute ischemia have not been clarified.In acutely ischemic porcine myocardium, we recorded transmural unipolar and bipolar electrocardiograms and mid-myocardial extracellular K(+) ([K(+)]e) from the center of the ischemic zone during 8-minute episodes of ischemia. Two different STTAs occurred.

Stress-induced ST elevation with or without concomitant ST depression is predictive of presence, location and amount of myocardial ischemia assessed by myocardial perfusion SPECT, whereas isolated stress-induced ST depression is not.

Background: Evaluation of stress-induced ST deviations constitutes a central part when interpreting the findings from an exercise test. The aim of this analysis was to assess the pathophysiologic correlate of stress-induced ST elevation and ST depression with regard to presence, amount and location of myocardial ischemia as assessed by myocardial perfusion SPECT (MPS) in patients with suspected coronary artery disease.

Methods And Results: 226 patients who had undergone bicycle stress test in conjunction with MPS were included.

Prominent R wave in ECG lead V1 predicts improvement of left ventricular ejection fraction after cardiac resynchronization therapy in patients with or without left bundle branch block.

Background: QRS morphology on postprocedural ECG indicating posterolateral left ventricular pacing may be predictive of response to cardiac resynchronization therapy (CRT).

Objective: The purpose of this study was to assess whether a positive vector in V1 and/or negative vector in lead I on the first postprocedural ECG, suggesting posterolateral capture from CRT, correlates with improvement in left ventricular ejection fraction (LVEF).

Methods: A retrospective chart review was conducted on all patients who underwent CRT implantation at our institution between April 2008 and December 2011.

Common pitfalls in the interpretation of electrocardiograms from patients with acute coronary syndromes with narrow QRS: a consensus report.

Acute coronary syndromes (ACS) with narrow QRS are divided into 2 groups: ST-elevation ACS that requires emergency percutaneous coronary intervention, and non-ST elevation ACS. The classification of ACS into these 2 groups is not always straightforward. In this document, we discuss several electrocardiogram patterns of acute ischemia that are often misinterpreted.

Should electrocardiogram criteria for the diagnosis of left bundle-branch block be revised?

In this study, we consider the proposition that the criteria for the electrocardiographic (ECG) diagnosis of left bundle-branch block (LBBB) be revised, a proposition born from analysis of results of cardiac resynchronization therapy trials. The various ECG definitions for LBBB (or lack thereof) used in these trials are reviewed as are the results of the analysis of ECGs from patients with left ventricular conduction disturbances by Grant and Dodge (Am J Med. 1956;20:834-852) and the criteria for the ECG diagnosis of LBBB recommended by the World Health Organization and the International Society and Federation for Cardiology in 1985.

Repolarization heterogeneity and rate dependency in a canine rapid pacing model of heart failure.

Background: Repolarization heterogeneity and rate dependency have long been established as factors contributing to arrhythmogenic risk. However, there are conflicting observations regarding the nature and extent of ventricular repolarization heterogeneity that complicate understanding of arrhythmogenic mechanisms. To explore these disparate findings, we studied ventricular repolarization heterogeneity and rate dependency in a canine, rapid pacing model of heart failure.

Report of the third International Society for Holter and Noninvasive Electrocardiology working group on improved electrocardiographic criteria for acute and chronic ischemic heart disease--Lund, Sweden: June 2010.

The third meeting of the International Society for Holter and Noninvasive Electrocardiology working group was convened in Lund, Sweden, in June 2010 to consider the key clinical challenge of developing electrocardiographic (ECG) criteria for identification of the global subendocardial ischemia that results from subtotal occlusion of either the left main coronary artery or its equivalent. The participants considered the specific abnormalities typical of global subendocardial ischemia on the presenting ECG and outlined further studies to establish the optimal quantitative ECG criteria. Subgroups on Electrocardiology, Myocardial Imaging, and Coronary Intervention met separately to establish priorities on their topic and then joined together in a final session of the entire working group.