A 62-year-old man with underlying COPD develops a viral upper respiratory infection and begins taking an over-the-counter decongestant. Shortly thereafter he experiences palpitations and presents to the emergency room, where the following rhythm strip is obtained.
What is the most likely diagnosis?
The rhythm strip reveals atrial flutter with 4:1 atrioventricular (AV) block. Atrial flutter is characterized by an atrial rate of 250 to 350/minute; the electrocardiogram typically reveals a sawtooth baseline configuration characteristic of flutter waves. In this strip, every fourth atrial depolarization is conducted through the AV node, resulting in a ventricular rate of 75/minute (although 2:1 conduction is more commonly seen). The rapid atrial rate excludes sinus rhythm (where the atrial and ventricular rates are the same) and junctional rhythm. In PAT the atrial rate is around 150, and inverted P waves usually follow the QRS complexes because of retrograde atrial conduction from the impulse that starts in the AV node. Regular atrial depolarizations at a rate of 300/minute (as in this case) would exclude PAT.
. A 32-year-old man presents to your office with concern about progressive fatigue and lower extremity edema. He has experienced decreased exercise tolerance over the past few months, and occasionally awakens coughing at night. Past medical history is significant for sickle cell anemia and diabetes mellitus. He has had multiple admissions to the hospital secondary to vaso-occlusive crises since the age of 3. Physical examination reveals a displaced PMI, but is otherwise unremarkable. ECG shows a first-degree AV block and low voltage. Chest x-ray shows an enlarged cardiac silhouette with clear lung fields. Which of the following would be the best initial diagnostic approach?
The patient’s history of sickle cell disease should raise the suspicion of iatrogenic iron overload. Multiple transfusions in a patient whose anemia is not attributed to blood loss lead to tissue iron accumulation and end-organ damage just like genetic hemochromatosis. Measures to assess body iron status (transfer-rin saturation, serum ferritin level) are the initial diagnostic studies. This patient’s diabetic status may also be related to iron accumulation. Evidence of cardiomegaly (from physical examination and chest x-ray) together with a low voltage on ECG suggests an infiltrative process affecting the heart. Brainnatriuretic peptide (BNP) is released from the cardiac myocytes in response to ventricular stretch and can be a useful tool in determining whether someone is suffering from heart failure. BNP will not, however, help determine the cause of the heart failure. Holter monitoring and cardiac catheterization are not necessary in patients without evidence of intermittent arrhythmias or coronary ischemia respectively. CT of the chest is used to assess lung nodules or parenchymal abnormalities (such as interstitial lung disease) but would not be useful in this patient with clear lung fields on CXR.
You are volunteering with a dental colleague in a community indigent clinic. A nurse has prepared a list of patients who are scheduled for a dental procedure and may need antibiotic prophylaxis beforehand. Of the patients listed below, who would be most likely to benefit from antibiotic prophylaxis to prevent infective endocarditis?
Recommendations for prophylaxis of infective endocarditis (IE) from transient bacteremia associated with dental, genitourinary, or gastrointestinal procedures have recently undergone major revision. Only patients with history of prior infective endocarditis (IE), patients with prosthetic heart valves, patients with unrepaired congenital cyanotic heart disease, and patients with prosthetic graft material which has not yet endothelialized (typically 6 months from placement of the graft material) are given prophylactic antibiotics. Therefore, the patients with coarctation of the aorta, repaired VSD, mitral valve prolapse, and aortic stenosis do not require pretreatment. A typical adult prophylactic regimen is a single dose of amoxicillin 2 g orally 30 to 60 minutes prior to the procedure. Any dental procedure that causes bleeding can cause transient bacteremia. Sterile procedures (ie, cardiac catheterization) and procedures with a very low risk of bacteremia (ie, endoscopy without biopsy) do not need preprocedure antibiotics.
A 60-year-old woman develops chest pain, respiratory distress, and confusion after right hip replacement surgery. She is confused and appears in respiratory distress. Blood pressure is 80/50, heart rate of 155/minute. ECG reveals atrial fibrillation. Which of the following is the best management of this patient’s arrhythmia?
This woman has hemo-dynamically unstable atrial fibrillation which requires immediate electrical cardioversion. Chemical cardioversion with metoprolol or adenosine is not appropriate because these drugs may further worsen her hypotension. Though embolic stroke is a concern during cardioversion, the benefit of promptly stabilizing the patient’s hemodynamic compromise outweighs this risk. With atrial fibrillation, synchronized cardioversion (which delivers an electric shock timed to the R wave of QRS complex on the EKG) is preferred. Defibrillation using an unsynchronized electric shock of 360 J is used in ventricular fibrillation and pulseless ventricular tachycardia. In the absence of hemodynamic compromise, the initial goals in the management of atrial fibrillation are (1) ventricular rate control, and (2) prevention of embolic stroke by anticoagulation. Ventricular rate control is best established with beta-blockers and/or calcium channel blocking agents (such as verapamil or diltiazem). These can be given by oral or intravenous route depending on the ventricular rate and clinical status of the patient. Digoxin may be added for rate control. The use of antiarrhythmic such as amiodarone can be instituted once sinus rhythm has been established or in anticipation of cardioversion in an attempt to maintain sinus rhythm. In the long-term management of atrial fibrillation, clinical trials have established no advantage for rhythm control over rate control.
An 18-year-old man military recruit reports several episodes of palpitation and syncope over the past several years. Physical examination is unremarkable. His ECG is shown below.
What is the most likenosis?
The ECG reveals shortened PR interval and a delta wave causing widening of the QRS. The delta wave is a “slurring” of the upstroke of the R wave caused by the early depolarization of ventricular myocardium. This is consistent with an accessory conduction pathway or WPW. The aberrant conduction tissue bypasses the normal AV node (hence the PR interval of < 0.20 seconds); it leads the electrical impulse directly to the ventricle (bypassing the His-Purkinje fibers and widening the QRS complex). Q waves are not infrequent and can be mistaken for evidence of prior MI. Myocardial infarction, however, does not cause shortened PR interval or delta wave. This patient’s QT interval is normal (< 0.45 second). Patients with HOCM usually have voltage criteria for left ventricular hypertrophy and prominent ST/T-wave changes but may also have large Q waves owing to hypertrophy of the septum. Rheumatic mitral stenosis would cause left atrial enlargement and perhaps atrial fibrillation, not the changes seen on this ECG.
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