New Concepts in the Assessment of Syncope
New Concepts in the Assessment of Syncope
There are 2 main reasons for evaluating a patient with syncope: 1) to assess the prognostic risk, including death, severe adverse events, and syncope recurrence; and 2) to identify the specific cause of the loss of consciousness to apply an effective mechanism-specific treatment strategy. Defining the mechanism is a prerequisite for finding a specific therapy to prevent recurrences. The ESC guidelines, which are summarized in the algorithm shown in Figure 2, address both issues.
(Enlarge Image)
Figure 2.
The Diagnostic Algorithm of a Patient Presenting With TLOC of Suspected Syncopal Nature
For explanation, see text. ECG = electrocardiogram; TLOC = transient loss of consciousness.
The first step in the evaluation of a patient presenting with TLOC of suspected syncopal nature consists of obtaining a detailed history and conducting a physical examination including orthostatic blood pressure (BP) measurements and standard ECG. In selected cases, the initial evaluation may also include echocardiography and in-hospital ECG monitoring (i.e. telemetry) neurological consultation, and blood tests. The initial evaluation may lead to a certain diagnosis in the situations listed in Table 2 . Under these circumstances, no further testing is required, and treatment can be initiated as needed. It is important to recognize that the diagnostic yield of the initial evaluation depends on the clinical setting in which the patient is being evaluated. In 2 large multicenter trials, a diagnosis was established in 50% of patients evaluated in the ED and in 21% of the more "difficult" patients referred to specialized syncope units. Reflex syncope (vasovagal, situational) accounted for approximately two-thirds of the diagnoses in both settings. Arrhythmic syncope was the second most frequent cause of syncope, accounting for 10% of the cases.
The second step in the evaluation of a patient presenting with TLOC is to assess the probability of developing serious clinical events within days or weeks of the index presentation. This risk assessment will determine the need for immediate hospitalization and early intensive evaluation (Fig. 2, Table 3 ).
A recent literature review performed by a task force of the Canadian Cardiovascular Society showed that on average 7.5% of patients referred to the ED had nonfatal severe outcomes while in the ED and 4.5% had nonfatal severe outcomes in the subsequent 7- to 30-day period. Severe outcome was defined as new diagnosis, clinical deterioration, syncope recurrence with serious injury, or significant therapeutic intervention. Furthermore, only 0.7% of patients died within the same time period. Thus, only a small minority of patients referred to the ED is likely to benefit from urgent assessment, and even a smaller subset requires hospitalization. The challenge resides in accurately identifying patients with high short-term risk. Table 3 summarizes the recommendations of the ESC and the Canadian Cardiovascular Society regarding the immediate need for hospitalization or urgent evaluation. In 3 validation studies that used the ESC criteria, the admission rate ranged between 38% and 42%. These admission rates remained significantly higher than the rate of developing a serious event shortly after the index presentation. Syncope facilities have been introduced to decrease the number of hospitalizations by offering the patient a well-defined rapid alternative evaluation pathway.
When the preceding high-risk features are absent, or when they are present with a subsequent negative workup, the risk of developing a life-threatening event is low. Indeed, in most of these cases, the events are reflex mediated and the prognosis is good. In patients at low risk with suspected cardiac syncope or reflex syncope with severe presentation due to the unpredictable nature of the events or their occurrence in high-risk settings, outpatient evaluation with referral to a specialized syncope facility is preferred. In patients with suspected reflex syncope with rare or mild symptoms, no further investigation is generally warranted. In these instances, patients can be educated and reassured about the benign nature of their symptoms (Fig. 2). In patients at low risk with severe presentation due to the unpredictable nature of the events or their occurrence in high-risk settings, outpatient evaluation with referral to a specialized syncope facility is preferred.
Diagnostic Algorithm
There are 2 main reasons for evaluating a patient with syncope: 1) to assess the prognostic risk, including death, severe adverse events, and syncope recurrence; and 2) to identify the specific cause of the loss of consciousness to apply an effective mechanism-specific treatment strategy. Defining the mechanism is a prerequisite for finding a specific therapy to prevent recurrences. The ESC guidelines, which are summarized in the algorithm shown in Figure 2, address both issues.
(Enlarge Image)
Figure 2.
The Diagnostic Algorithm of a Patient Presenting With TLOC of Suspected Syncopal Nature
For explanation, see text. ECG = electrocardiogram; TLOC = transient loss of consciousness.
Initial Evaluation: The Value of History Taking and Standard ECG
The first step in the evaluation of a patient presenting with TLOC of suspected syncopal nature consists of obtaining a detailed history and conducting a physical examination including orthostatic blood pressure (BP) measurements and standard ECG. In selected cases, the initial evaluation may also include echocardiography and in-hospital ECG monitoring (i.e. telemetry) neurological consultation, and blood tests. The initial evaluation may lead to a certain diagnosis in the situations listed in Table 2 . Under these circumstances, no further testing is required, and treatment can be initiated as needed. It is important to recognize that the diagnostic yield of the initial evaluation depends on the clinical setting in which the patient is being evaluated. In 2 large multicenter trials, a diagnosis was established in 50% of patients evaluated in the ED and in 21% of the more "difficult" patients referred to specialized syncope units. Reflex syncope (vasovagal, situational) accounted for approximately two-thirds of the diagnoses in both settings. Arrhythmic syncope was the second most frequent cause of syncope, accounting for 10% of the cases.
Assessment and Management of Patients With a High Short-term Risk
The second step in the evaluation of a patient presenting with TLOC is to assess the probability of developing serious clinical events within days or weeks of the index presentation. This risk assessment will determine the need for immediate hospitalization and early intensive evaluation (Fig. 2, Table 3 ).
A recent literature review performed by a task force of the Canadian Cardiovascular Society showed that on average 7.5% of patients referred to the ED had nonfatal severe outcomes while in the ED and 4.5% had nonfatal severe outcomes in the subsequent 7- to 30-day period. Severe outcome was defined as new diagnosis, clinical deterioration, syncope recurrence with serious injury, or significant therapeutic intervention. Furthermore, only 0.7% of patients died within the same time period. Thus, only a small minority of patients referred to the ED is likely to benefit from urgent assessment, and even a smaller subset requires hospitalization. The challenge resides in accurately identifying patients with high short-term risk. Table 3 summarizes the recommendations of the ESC and the Canadian Cardiovascular Society regarding the immediate need for hospitalization or urgent evaluation. In 3 validation studies that used the ESC criteria, the admission rate ranged between 38% and 42%. These admission rates remained significantly higher than the rate of developing a serious event shortly after the index presentation. Syncope facilities have been introduced to decrease the number of hospitalizations by offering the patient a well-defined rapid alternative evaluation pathway.
Outpatient Evaluation and Management of Patients With a Low short-term Risk
When the preceding high-risk features are absent, or when they are present with a subsequent negative workup, the risk of developing a life-threatening event is low. Indeed, in most of these cases, the events are reflex mediated and the prognosis is good. In patients at low risk with suspected cardiac syncope or reflex syncope with severe presentation due to the unpredictable nature of the events or their occurrence in high-risk settings, outpatient evaluation with referral to a specialized syncope facility is preferred. In patients with suspected reflex syncope with rare or mild symptoms, no further investigation is generally warranted. In these instances, patients can be educated and reassured about the benign nature of their symptoms (Fig. 2). In patients at low risk with severe presentation due to the unpredictable nature of the events or their occurrence in high-risk settings, outpatient evaluation with referral to a specialized syncope facility is preferred.