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What are cardiac dysrhythmias?

This is an excerpt from Guidelines for Cardiac Rehabilitation Programs 6th Edition With Web Resource by AACVPR.

By Alison L. Bailey, Alexis L. Beatty, Brian Carlin, Dennis J. Kerrigan, Steven J. Keteyian, Kirstine Laerum Sibilitz, Karen Lui, Ryan Mays, Jonathan Powell, Ray W. Squires, Diane J. Treat-Jacobson

Cardiac dysrhythmias are abnormalities in heart rhythm. They are also known as arrhythmias or irregular rhythms. Many CR participants have a history of cardiac dysrhythmias, and some experience dysrhythmias during CR participation.1-3 Symptoms from dysrhythmias may or may not be present and vary from patient to patient. The effects of dysrhythmias can range from generally benign to potentially harmful. Most studies report a cardiac arrest rate of approximately 1/100,000 patient-hours of CR participation.4-7 Although it is rare for dysrhythmias to have life-threatening consequences during exercise in CR programs, it remains important to recognize dysrhythmias and their features.

Bottom Line

Cardiac dysrhythmias are common in CR participants. Life-threatening consequences of cardiac dysrhythmias are rare during exercise in CR programs.

The following are commonly encountered dysrhythmias and symptoms:

Cardiac Dysrhythmias in CR

Generally Benign

  • Premature atrial complexes (PACs)
  • Isolated premature ventricular complexes (PVCs)
  • AF or atrial flutter with controlled ventricular rate (8
  • Paroxysmal supraventricular tachycardia (SVT)
  • Mild bradycardia (50-60 bpm)
  • First-degree atrioventricular (AV) block and asymptomatic type I second-degree (also known as Wenckebach) AV block

Potentially or Likely Harmful

  • AF or atrial flutter with a rapid rate (≥110 bpm at rest)
  • Symptomatic or severe bradycardia (HR <50)
  • Symptomatic or advanced AV block (type II second-degree AV block or complete heart block)
  • Ventricular tachycardia
  • Ventricular fibrillation

Symptoms Associated With Cardiac Dysrhythmias

Stable Symptoms

  • Palpitations
  • Dizziness or lightheadedness
  • Shortness of breath
  • Chest pain or discomfort

Nonspecific or Associated Symptoms

  • Weakness or fatigue
  • Sweating
  • Blurred vision
  • Nausea
  • Anxiety
  • Edema

Unstable Symptoms

  • Hypotension
  • Near-syncope or loss of consciousness
  • HF
  • Unstable angina or MI
  • Cardiac arrest

Exercise induces many physiologic effects, which can have both direct and indirect effects on cardiac electrophysiology. Exercise intensity can be related to the occurrence of dysrhythmias. Some dysrhythmias diminish or disappear with increasing exercise intensity; others increase or appear with increasing exercise intensity; and still others have no observable relationship to exercise intensity. Factors that can contribute to dysrhythmias during exercise include autonomic nervous system activity, ischemia, genetic abnormalities, structural heart disease, medications with proarrhythmic side effects, electrolyte imbalance, dehydration, and certain environmental factors.

Guideline 10.7 Dysrhythmia Exercise Prescription

For patients with known dysrhythmias, the exercise prescription should be tailored to the individual, with predetermined goals and criteria for exercise termination. Exercise should be terminated when a patient experiences a potentially harmful dysrhythmia or dysrhythmia with unstable symptoms.

Atrial Fibrillation

Light-to-moderate activities, particularly leisure-time activity and walking, are associated with a significantly lower incidence of AF in older adults.9 However, people who participate in extreme endurance training and sports activities may have an increased incidence of AF.10,11 For those diagnosed with AF, regular moderate PA is known to increase exercise capacity and control ventricular rate.12,13 In addition, exercise training increases exercise capacity and may reduce AF burden.14,15 The following information provides specific information about CR participation in patients who have AF.

AF originates in the atrium and is the most common cardiac arrhythmia. It is characterized by irregular contractions of the muscle fibers of the atria resulting in a variable HR. Risk factors associated with developing AF include PA, obesity, advanced age, HTN, HF, diabetes mellitus, CVD and valvular heart disease, left ventricular and atrial enlargement, and hyperthyroidism.43 Paradoxically, despite having few risk factors, athletes are also at increased risk for developing AF.

CR professionals will encounter these two types of patients with AF: patients who experience an initial (acute) onset (often noted during CR check-in or during exercise) and patients previously diagnosed and medically managed. Generally, AF is classified as (1) paroxysmal, (2) persistent, (3) long-standing persistent, or (4) permanent.2

AF should be considered when a patient presents with a rapid (often >110 bpm) “irregularly irregular” (no rhythmic pattern) resting HR. Patients experiencing an abrupt onset of AF may or may not report accompanying symptoms including palpitation, tachycardia, fatigue, shortness of breath, dizziness, and nausea. If AF is suspected, an ECG will confirm a diagnosis.

If new-onset AF is confirmed, the patient's physician should be consulted. Treating new-onset AF has three goals.44,50 The first goal is to mitigate symptoms by initially focusing in on reducing HR. Typical therapeutic HR reduction options include beta-adrenergic and calcium channel blocking agents and antiarrhythmic medication. The second goal is to reduce the risk for the development embolization of a blood clot (which the patient is at risk of developing due to atrial blood stagnation) through anticoagulation therapy. The third goal is to manage the patient's cardiovascular risk factors, which for overweight or obese patients is recommended to include weight loss and risk factor modification.50

Safety and rates of adverse event of exercise in patients have not been well studied. No large randomized control trials of exercise training and AF have assessed safety and efficacy. Guidelines for the treatment of patients with AF do not explicitly endorse specific exercise recommendations. Exercise, however, is not contraindicated in patients with AF. Moreover, exercise is effective treatment in multiple risk factors associated with AF, such as physical inactivity, HTN, diabetes mellitus, and obesity. Therefore, asymptomatic patients with AF who have received medical clearance should be encouraged to participate in an exercise program.

However, AF can profoundly impact the physiologic response to exercise training.45 In particular, the rapid, irregular contraction of the atrium results in reduced ventricular output. To compensate for the reduced cardiac output there is a commensurate increase in the rate and irregularity of ventricular contraction. Despite the negative impact of AF, exercise training studies have demonstrated improvements in functional capacity, health status, and quality of life.46

The special consideration regarding exercise testing and prescription for patients with AF have been detailed elsewhere.3 The following section is a brief review of special considerations regarding exercise testing and prescription for CR participants with AF.

Exercise Testing

As with all patients entering CR, undergoing a symptom-limited exercise tolerance test prior to initiating an exercise training program is optimal but not required. An exercise test is useful to assess for myocardial ischemia, evaluate chronotropic response, identify signs and symptoms, quantify functional capacity, and establish some general parameters for exercise training intensity.

Exercise Prescription for Patients With AF

Currently, no specific recommendations exist regarding exercise training for the treatment of AF. Studies of exercise training in patients with AF have employed a variety of protocols. Components of any exercise prescription include frequency, intensity, duration, modality, progression, and total volume. The exercise prescription for patients with AF should be individualized. A meta-analysis of exercise training studies involving people with AF recommends that a training regimen should include three or more sessions per week of a combination of moderate-intensity aerobic activity and resistance training. Session duration should be approximately 60 minutes, including adequate warm-up and cool-down.

By definition, the HR for a person with AF is irregular. Therefore, use of HR exclusively to assess exercise intensity is problematic. For aerobic training, in lieu of HR, use of RPE scale is an effective means to assess exercise intensity. A rating of 11 to 14 (on the Borg 6-20 scale) is typically associated with a moderate intensity that is approximately 70% to 85% of peak exercise capacity. Notably, very few studies have focused on the safety and efficacy of high-intensity aerobic training in patients with AF.

For overweight patients with AF, weight loss is recommended.47,50 To facilitate weight loss, orienting the exercise prescription to maximize caloric expenditure is indicated. High caloric exercise training (e.g., treadmill walking at a moderate intensity for an extended duration) in CR is well tolerated and an effective strategy to promote weight loss and improve multiple cardiovascular risk factors.48

No specific guidelines exist for resistance training for patients with AF. Given the lack of recommendations, using professional discretion is necessary when providing guidance regarding resistance training. Following the resistance training recommendations for other, non-AF CR participants is advisable. General recommendations for resistance training are found in chapter 6.

More Excerpts From Guidelines for Cardiac Rehabilitation Programs 6th Edition With Web Resource