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CHAPTER 10 Cardiac dysrhythmias
Christian C. Knutsen and Donald M. Yealy
Introduction
EMS physicians often use the same approach in the field and the hospital to provide patient care, even though the goals in each area differ. The care of patients with dysrhythmias (defined as any change from normal cardiac electrical rhythm and often used interchangeably with arrhythmia) before hospital arrival focuses on treating all life‐threatening or imminently life‐threatening rhythm changes within minutes. Precision about the specific rhythm change is not the goal of early care, though the information gained during this interval can later aid that task. In the emergency department and in the hospital, more time is available to identify the specific rhythm disturbance and titrate more carefully the next and eventual long‐term treatment.
This chapter discusses a pragmatic method of providing medical oversight and field clinical care for non‐arrest dysrhythmias. We highlight the most important field observations and actions to help focus the approach when giving direct medical oversight, creating written protocols, or providing direct patient care. We offer a “low tech” approach to the problems, emphasizing simple tools, including a brief history, physical examination, and standard 3‐ or 12‐lead field ECG. Similarly, we focus on interventions that are effective and easily provided in the field. In general, the approach offered is consistent with the American Heart Association advanced cardiac life support guidelines, although we highlight areas where simplified or alternative approaches exist.
Evaluation
Three basic sources of information exist during the assessment of field dysrhythmias: patient history, physical examination, and the ECG. Rarely will any one of these suffice in guiding treatment. Rather, all three considered together guide care [1, 2]. Four steps can be used to manage patients. Treatment decisions often can be made before completing all steps, allowing an economy of effort.
Step one: identify symptoms and how they relate to the rhythm
Two groups of patients present with dysrhythmias: asymptomatic patients with incidental rhythm changes and patients with symptomatic rhythm changes. Incidental dysrhythmias may relate to the symptoms, but are the result of a noncardiac problem and do not worsen the immediate outcome. Usually, these patients have normal or near normal vital signs. Patients with incidental dysrhythmias, or who are asymptomatic, rarely require field rhythm‐directed treatment. Those with incidental dysrhythmias typically require treatment of any underlying acute condition (e.g., analgesia for pain or IV fluids for hypovolemia).
Example: A 67‐year‐old male patient with a history of “extra heart beats” transported for an isolated ankle injury displays a sinus tachycardia (from pain) and occasional premature ventricular complexes, but no other symptoms or abnormalities on physical examination. He requires splinting and analgesia, not antidysrhythmics. This should not be confused with dysrhythmias with symptoms, such as tachycardia or bradycardia associated with chest pain, weakness, breathing difficulties, or syncope.
Step two: identify stable and unstable patients
Because asymptomatic or incidental dysrhythmias usually require no direct treatment, the prehospital focus shifts to those dysrhythmias associated with symptoms. These patients are classified based on the severity of symptoms as either stable or unstable. Although many patients have symptoms attributable to the change from a “normal” rhythm, most tolerate these well and are stable. However, unstable patients are likely to suffer harm or deteriorate. EMS clinicians must identify these unstable patients and intervene promptly.
Unstable patients have signs and symptoms of impaired end‐organ perfusion due to the rhythm disturbance [2]. A few brief historical questions and physical examination features identify these patients early in their evaluations.
Hypotension–often defined as a systolic blood pressure below 90 mmHg, a mean arterial pressure <65 mmHg, or a drop of systolic blood pressure >40 mmHg from a known baseline.
Cardiac dysfunction–manifest as chest pain, shortness of breath, or rales, each signifying inadequate myocardial perfusion or function.