Medical Blog

Wolff-Parkinson-White Syndrome

Introduction
Background

Preexcitation was defined by Durrer et al in 1970 with the following statement, “Preexcitation exists, if in relation to atrial events, the whole or some part of the ventricular muscle is activated earlier by the impulse originating from the atrium than would be expected if the impulse reached the ventricles by way of the normal specific conduction system only.”1 In preexcitation, atrial impulses bypass the typical electrical pathway that conducts via the atrioventricular node and activates the ventricular myocardium directly via an accessory pathway. Of the various preexcitation syndromes, the most common is Wolff-Parkinson-White (WPW) syndrome. Emergency departments should be familiar with this syndrome and the proper treatment of its associated dysrhythmias to minimize morbidity and mortality.
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Review of Cardiac Tests

Introduction

The goal of cardiac testing is to help stratify patients thought to be at risk for coronary artery disease. Risk stratification of chest pain patients in the emergency department (ED) also includes interpretation of the history, physical examination, ECG, and cardiac biomarkers. Cardiac testing encompasses diagnostic coronary angiography (invasive) or a variety of noninvasive tests. This article focuses on the noninvasive testing modalities. These include exercise stress testing, pharmacologic stress testing, myocardial perfusion imaging, stress echocardiography, and cardiac CT and MRI. The noninvasive tests can be performed on an outpatient basis, in a physician’s office, in a hospital, or for observation unit and admitted patients.

An understanding of these tests is important to the emergency physician (EP) for two primary reasons. First, patients frequently present that have undergone prior noninvasive testing. Knowing the value and limitations of that testing can be essential to the care of such patients. Second, with the recent expansion of observation medicine, it has become the responsibility of emergency physicians to choose and utilize the results of noninvasive cardiac testing in many hospitals. Noninvasive cardiac testing is an important adjunct to the broader scheme used to risk stratify chest pain patients. Use of cardiac biomarkers alone without additional noninvasive testing has not been shown to confer a low-enough risk to safely discharge a large proportion of emergency department chest pain patients.1, 2, 3
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Pulmonic Valvular Stenosis

Introduction
Background

Until the 1950s, isolated pulmonary stenosis was considered to be a rare congenital abnormality.1 A review of the literature in 1949 yielded just 68 cases. However, as physiologic testing has improved, this condition has been more frequently recognized.

Pulmonary valve stenosis (PVS) is described as those lesions that collectively are associated with obstruction to right ventricular outflow. PVS may be valvular, subvalvular, or supravalvular. PVS is the cause of isolated right ventricular outflow obstruction in 80% of cases.2
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Premature Ventricular Contraction

Introduction
Background

Premature ventricular contraction (PVC) is caused by an ectopic cardiac pacemaker located in the ventricle. PVCs are characterized by premature and bizarrely shaped QRS complexes usually wider than 120 msec on with the width of the ECG. These complexes are not preceded by a P wave, and the T wave is usually large, and its direction is opposite the major deflection of the QRS.

The clinical significance of PVCs depends on their frequency, complexity, and hemodynamic response.

For additional information, see Medscape’s Cardiology Specialty page.

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Peripheral Vascular Disease

Introduction
Background

Peripheral vascular disease (PVD) is a nearly pandemic condition that has the potential to cause loss of limb or even loss of life. Peripheral vascular disease manifests as insufficient tissue perfusion caused by existing atherosclerosis that may be acutely compounded by either emboli or thrombi. Many people live daily with peripheral vascular disease; however, in settings such as acute limb ischemia, this pandemic disease can be life threatening and can require emergency intervention to minimize morbidity and mortality.
Pathophysiology
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Pericarditis and Cardiac Tamponade

Introduction
Background

Pericarditis and cardiac tamponade are clinical problems that involve the potential space surrounding the heart or pericardium. Pericarditis is one cause of fluid accumulation in this potential space; cardiac tamponade is the hemodynamic result of fluid accumulation.

The use of limited echocardiography by emergency physicians has enhanced the diagnosis of cardiac tamponade from various causes, including trauma and infectious and noninfectious etiologies.

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Patent Ductus Arteriosus

Introduction
Background

Patent ductus arteriosus (PDA) is the persistence of a normal fetal structure between the left pulmonary artery and the descending aorta. Persistence of this fetal structure beyond 10 days of life is considered abnormal.

For a related CME/CE activity, see CME/CE - A Newborn Presenting in Extremis.
Pathophysiology

The ductus is derived from the 6th aortic arch. From the 6th week of fetal life onwards, the ductus is responsible for most of the right ventricular outflow. It contributes to 60% of the total cardiac output throughout the fetal life. Only about 5-10% of its outflow passes through the lungs. The ductus arteriosus is an important structure in fetal development as it contributes to the flow of blood to the rest of the fetal organs and structure. Closure of the ductus before birth may lead to right heart failure. At birth, the ductus normally undergoes closure.
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Myopathies

Introduction
Background

Myopathy is a muscle disease unrelated to any disorder of innervation or neuromuscular junction. Etiologies vary widely. The common symptoms are muscle weakness, impaired function in activities of daily life, and, rarely, muscle pain and tenderness. Presence of discolored or dark urine suggests myoglobinuria.
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Myocarditis

Introduction

Background

Myocarditis is collection of diseases of infectious, toxic, and autoimmune etiologies characterized by inflammation of the heart. Subsequent myocardial destruction can lead to dilated cardiomyopathy. Myocarditis is an elusive illness to study, diagnose, and treat because the clinical presentation may range from nearly asymptomatic to overt heart failure requiring transplantation; a myriad of causes exist, and it is occasionally the unrecognized culprit in cases of sudden death. Read more…

Myocardial Infarction

Introduction

Background

Myocardial infarction (MI) is the rapid development of myocardial necrosis caused by a critical imbalance between oxygen supply and demand of the myocardium. This usually results from plaque rupture with thrombus formation in a coronary vessel, resulting in an acute reduction of blood supply to a portion of the myocardium. Read more…