Diagnosing Syncope in the Elderly
Rodrigo B. Cavalcanti, MD, FRCP(C)
Clinical Assistant, Internal Medicine, University Health Network.
Shabbir M.H. Alibhai, MD, MSc, FRCP(C)
Staff Physician, Internal Medicine and Geriatrics,
University Health Network, Lecturer, Dept. of Medicine,
University of Toronto, Toronto, ON.
Introduction
Syncope is defined as a transient loss of consciousness accompanied by a loss of postural tone, followed by complete, spontaneous recovery.1 Population-based studies, such as the Framingham study, indicate that the overall incidence of syncope is 3% per year for men and 3.5% per year for women.2 Moreover, syncopal events become more frequent with age, with the incidence rising to 6% per year in persons over 75 years of age.2
It is important to note that syncope is fundamentally a symptom, rather than a disease process, with multiple conditions giving rise to this symptom. The common step in most etiologies is a transitory compromise in cerebral blood flow. Impairment in blood flow to the reticular activating system in the brainstem results in loss of consciousness, while lack of perfusion to the corticospinal pathways impairs motor tone.
Currently, it is estimated that between 2-6% of all hospital admissions are for evaluation of syncope or treatment of associated falls, 80% of which are in persons aged 65 years or older.3 When one considers that this is the fastest growing demographic group in North America, the growing importance of syncope in the elderly as a health concern becomes apparent.
Differential Diagnosis
The list of potential causes of syncope is extensive. The most common etiologies are listed in Table 1. The main categories include cardiac, vasovagal, situational, neurological, orthostatic and psychogenic causes.
Cardiac syncope deserves special consideration since it is associated with a worse prognosis than are non-cardiac etiologies. It is estimated that mortality following cardiac syncope is as high as 30% in the first year after the event, rising to 50% after five years.4 Among cardiac causes, arrhythmias account for three-quarters of syncopal episodes in most series.5 The presence of structural heart disease, be it coronary artery disease, valvular abnormalities or impairment in ventricular function, increases the risk of arrhythmic syncope. Moreover, in patients with established heart disease, even non-cardiac causes of syncope carry a higher risk of mortality compared to those with no heart disease.
Vasovagal syncope refers to disorders affecting the reflex regulation of vascular tone, heart rate, or both. This group accounts for the majority of syncopal events in younger adults, but is less prevalent in older age groups.6 In fact, only 1-5% of elderly patients with syncope receive this diagnosis.7 Typically, emotionally charged or painful situations, trauma or exertion precede vasovagal syncope. Patients will often relate a history of sudden pallor, followed by nausea, diaphoresis and blurred vision. This type of syncope may also be aborted if a sitting or recumbent posture is readily adopted.
Situational syncope is commonly related to conditions that produce a Valsalva manoeuvre. Mechanisms include decreased preload coupled with cardio-inhibitory and vasodepressor reflexes produced by central baroreceptors. Common triggers include micturition, defecation, heavy lifting and coughing. Men experiencing nocturia and straining on urination, such as those who suffer from benign prostatic hypertrophy, are at highest risk of this type of syncope.8 In this particular group, the cardiovascular system undergoes additional stresses from sudden standing and from the diuresis produced by their previous supine position.
Carotid sinus hypersensitivity is also prevalent in older age groups. It often produces an cardio-inhibitory response (profound drop in heart rate, sometimes resulting in asystole, without compensatory rise in blood pressure), but may also induce an abrupt vasodepressor