Chapter 18: Cardiac Rhythm Disturbances

GENERAL CONSIDERATIONS

INITIAL APPROACH TO THE STABLE PATIENT

The focused evaluation of the patient includes determining the presenting complaint(s), obtaining the medical history, identifying medication use, performing a physical examination, initiating continuous cardiac rhythm monitoring, reviewing the 12-lead ECG, and analyzing the cardiac rhythm on the rhythm monitor, a printed strip, or the ECG.

Presenting symptoms may include palpitations, lightheadedness, fatigue, or weakness. Ischemic symptoms, such as chest pain, nausea, dyspnea, or lightheadedness, may be due to dysrhythmia-induced ischemia.

The medication history includes prescribed medications, herbals, recreational drugs, and caffeine-containing beverages. Especially note recently started new medications or increased medication doses. Symptoms of hyperthyroidism should be sought. Patients with a family history of sudden death or syncope and those with organic heart disease have a higher risk of cardiac dysrhythmias and complications. Panic or anxiety is a diagnosis of exclusion in tachycardic ED patients.

INITIAL APPROACH TO THE UNSTABLE PATIENT

An unstable patient requires rapid assessment and treatment to prevent cardiovascular collapse. Instability as related to cardiac rhythm disturbances means that the dysrhythmia is (1) impairing perfusion and threatening vital organ function or (2) has the potential to deteriorate into cardiac arrest (Table 18-1).¹ Establish an IV line, initiate cardiac rhythm monitoring, obtain an ECG, and be prepared for drug or electrical therapy.

Dysrhythmia-induced chest pain results from coronary hypoperfusion, and dyspnea results from pulmonary edema, usually with objective evidence: ST-segment abnormalities, rales on examination, or low oxygen saturation. As the ventricular rate exceeds 220 beats/min, severe systemic hypoperfusion often results, increasing the opportunity for malignant ventricular dysrhythmias.

GENERAL APPROACH TO BRADYDYSRHYTHMIAS

Bradydysrhythmia describes rhythms with a ventricular rate slower than 60 beats/min in the adults and slower than age-appropriate heart rates in children. Bradydysrhythmias can be broadly categorized as bradycardias (atria and ventricles beat at the same slow rate) and atrioventricular (AV) blocks (ventricles beat slower than the atria).¹ The bradycardias include sinus bradycardia, junctional rhythm, idioventricular rhythm, atrial fibrillation/flutter with a slow ventricular response, and hyperkalemia-related sinoventricular rhythm. Bradydysrhythmias due to AV blocks include second-degree (usually type II) and third-degree AV block.

The most common bradycardia is sinus bradycardia, followed by junctional rhythm and, less commonly, idioventricular rhythm. These rhythms are found in both stable and unstable patients. Atrial fibrillation or flutter with slow ventricular response are uncommon; these rhythms are usually seen in patients ...