Rebecca L. Stepien, DVM, MS, Diplomate ACVIM (Cardiology), University of Wisconsin-Madison
The most common causes of sudden episodic collapse are cardiovascular or neurologic disease. Episodes usually last less than 1 minute, recovery to normality or near-normality occurs within minutes, and there is no repetitive motion reported in most cases. In contrast, seizure duration usually exceeds 3 minutes, and the animal typically exhibits motor activity during the event. Specific questions to ask the owner to help differentiate between the two include: What was the pet doing when the event occurred? What was the posture/degree and type of motion of the pet during the event? Did the pet look at you when you called his/her name? How long did the event last? Any evidence of cardiovascular abnormality upon examination, including abnormal heart rate or heart rhythm, detection of extra heart sounds or murmurs, or detection of poor perfusion via palpation of weak peripheral pulses or observation of abnormal capillary refill time is an indication for an in-depth investigation of the cardiovascular system. Findings that indicate involvement of the central nervous system include evidence of intracranial lesions or hypertension. Patients with evidence of intracranial disease can be examined further with imaging or evaluation of cerebrospinal fluid. Seizing patients should be evaluated for metabolic causes of seizures, including biochemical disturbances and polycythemia. Evaluation of systemic blood pressure should be routine, even in patients with a history of seizures, since elevations can be associated with intracranial hemorrhage or edema that may lead to seizures. Patients with abnormal cardiac rhythms responsible for syncope may present with a normal heart rate by auscultation, so an electrocardiogram is always indicated as part of the examination. Once the initial cardiovascular physical examination, electrocardiogram, and blood pressure evaluation are completed, thoracic radiographs and an echocardiogram are recommended to diagnose or exclude cardiac disease from the list of possible causes.
COMMENTARY: Patients with episodic collapse are often difficult to evaluate. At the point of the actual physical examination, the patient is fully recovered, and obtaining a history of the events leading up to and an exact description of the episode from the owner can be challenging. Without this critical information, establishing a list of differential diagnoses and prioritizing diagnostic tests can be frustrating. Therefore, interviewing the owner with a standard list of pointed questions simplifies the process of obtaining this information. A thorough history and physical examination are the best diagnostic tools available to the clinician and should be completed on all patients presented for evaluation of a sudden collapse.