● Aberrantly conducted beats after long-short R-R cycles known as Ashman phenomenon . The ECG is described as a wide QRS complex that follows a short R-R interval preceded by a long R-R interval. The wide QRS is often associated with a right bundle branch block. ● Left, right, or bi-atrial enlargement (identified by notched p waves). Atrial enlargement can predispose the patient to AF since changes in the structure of the heart can change electrical conduction. ● Left ventricular hypertrophy (LVH; R wave in AVL + S wave in V3 > 20-24 mm). LVH is a form of structural heart disease as noted in patients with hypertensive heart disease. ● Bundle-branch block (right or left) or “intraventricular conduction delay” is a prolonged QRS without the right or left bundle branch pattern. ● Acute or prior myocardial infarction (MI): Acute MI will have evidence of ST elevation or ST depression in contiguous leads; prior MI will have the presence of a Q wave (1/3 to ¼ the height of the R wave and 0.4 seconds wide). (Banasik & Copstead, 2018; McCance & Huether, 2019; Morillo et al., 2017; Pilgrim, 2018) Transesophageal echocardiography (TEE) is helpful for the following applications: Rule out an atrial thrombus, particularly in the left atrial appendage; Guide cardioversion (if thrombus is seen, cardioversion should be delayed); and The evaluation of the extent of valvular disease. ● Electrophysiology studies are used to map the electrical activity of the heart. During these studies, the heart team can stimulate the heart to create faster or slower rhythms. The mapping of the heart can determine the best location to apply cardiac ablation to control AF. The ablation, if effective, will create scar tissue to prevent further arrhythmias. Keep in mind that the ablation may not convert the patient from AF until the scar tissue has time to form, thus teaching the patient/family will lessen anxiety if the patient is not in NSR after the ablation. ● Stress testing is used to rule out ischemic etiology. If the patient’s risk factors do not indicate an ischemic etiology, this testing may not be indicated or can be delayed. A cardiac catheterization may be utilized to assess if ischemic heart disease is one of the etiologies of AF. In addition to assessing the coronary vasculature, the EF can be calculated. Typically, if the patient has a positive stress test that indicates stress- induced ischemia, a cardiac catheterization is then performed to identify the extent of disease and EF (Banasik & Copstead, 2018).
Figure 3: Brief Atrial Fibrillation Initiated by Early PAC (Arrow)
Note . Used with permission; Frank G. Yanowitz, MD, (Health Education Assets Library (HEAL)). ● Heart rates associated with AF can be controlled or fast (typically 110-140 beats/minute yet may go to 160-170 beats/minute). Fast ventricular rates are referred to as AF with rapid ventricular rate (RVR). Here, recall the diastolic filling time is compromised with fast heart rates, which can compromise cardiac output and coronary artery perfusion. In addition to the continuous ECG, a 12-lead electrocardiography (ECG) provides more data, including the following: Diagnostic testing: Beyond the ECG Other diagnostic testing for AF could include a chest X-ray, Holter monitor, echocardiogram, a transesophageal echocardiography (TEE), electrophysiology studies (EPS), and stress testing. These diagnostic tests assist the clinician in obtaining the differential diagnosis for the presence of AF to manage the comorbid conditions, as well as the sequelae of AF. ● The chest X-ray is utilized to evaluate for the presence of pneumonia, COPD, pulmonary vascular congestion, and cardiomegaly. As noted previously, the important concept to understand here is related to changes in the structure of the heart second to co-morbid conditions. For example, a patient with COPD can develop pulmonary hypertension, which affects right heart structural pathology, thereby increasing the incidence of atrial fibrillation. ● Holter monitor/event recorder can be utilized in an outpatient setting to obtain the diagnosis of AF not found on telemetry or a 12-Lead as related to the paroxysmal nature of AF. ● The echocardiogram identifies the presence of left ventricular hypertrophy (LVH), left and right atrial enlargement (LAE), ejection fraction (EF), presence of diastolic dysfunction, wall motion abnormalities (ischemic tissue can be reported as akinetic, hypokinetic, dyskinetic), valvular heart disease, and estimation of pulmonary systolic pressure, i.e., pulmonary hypertension (Pilgrim, 2018; Walsh & Caple, 2018). All of these changes to structure can change the function of the heart and electrical excitability.
COMPLICATIONS OF AF
Decreased cardiac output will depend on multiple factors, including the extent of structural heart disease, age, and functional status of the patient. As noted, the patient may be hemodynamically unstable based upon these factors, as well as symptomatic with signs and symptoms including chest pain, palpitations, dyspnea, dizziness, or hypotension. Cardiogenic Pharmacologic management The management of AF can be complex because of numerous pharmacologic interventions available to clinicians. Therefore, the RACE acronym can be used for simplicity: ● R is for rate control. ● A is for antiarrhythmic medications. ● C is for anti coagulation . ● E is for evaluation . The 2016 quality guidelines were updated in 2020 (Heidenreich et al., 2021) for managing patients as reported under the purview of the American Heart Association (AHA) and The
shock may be a result of AF. Thromboembolic events can be prevented through anticoagulation. Quality-of-life issues are related to the time in AF, recurrence of AF, the persistence of symptoms, frequency of hospitalizations/office visits, the extent of diagnostic testing, cost to the patient, etc.
American College of Cardiology (ACC). For rate control, rhythm control, and anticoagulation, numerous factors must be taken into consideration including, but not limited to: Age; length of time in AF; presence of heart failure (preserved or reduced); other co-morbid conditions; pharmacologic agent’s potential to prolong the QT interval; side effect profile; and potential for pharmacokinetic interactions (drug-drug and drug-nutrient interactions). An interdisciplinary heart team should individualize care to the patient and determine the best class of medication to utilize.
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