Syncope is defined as a sudden, transient loss of consciousness followed by spontaneous
complete recovery.14 It is caused by transient global cerebral hypoperfusion due to
decreased cardiac output, excessive vasodilatation, or both. The most common causes
include a)reflex (i.e., vasovagal syncope); b)cardiac syncope; and c)orthostatic
hypotension. Syncope accounts for 1-3% of ED visits and ~6% of admissions from the ED to
the hospital. Each year, syncope accounts for approximately 160,000 ED visits in Canada,
with direct hospital costs of approximately $130 million.
ED management of syncope: Overall, up to 10% of patients seen in the ED for syncope will
have serious underlying conditions e.g., serious arrhythmia, myocardial infarction,
significant hemorrhage, pulmonary embolism] identified and/or die from these conditions
within the next 30 days. Until recently, valid and reliable evidence to inform these
decisions has been lacking. Professional medical societies in Europe and North America
have long called for the development of practical and accurate tools to stratify patients
into low, intermediate, and high-risk groups to aid in management decisions. One-third to
half of these serious conditions will be identified ONLY AFTER they are either discharged
from the ED or hospitalized in an inpatient unit, emphasizing the challenge in risk
stratification and ED disposition decision-making. Of these serious conditions that are
identified after ED disposition, 68.8% are arrhythmias. While the non-arrhythmias are
identified in the first few days after the ED visit, arrhythmias tend to be identified up
to two weeks after the ED visit. The hypothesis is that prolonged live cardiac rhythm
monitoring of at-risk ED syncope patients, defined as those with CSRS score ≥3 discharged
from the ED, will lead to the identification of important arrhythmia or ruling out an
arrhythmic etiology and consequently to improved patient safety and lower healthcare
costs.
Preliminary work: Two large multicentre prospective studies were completed to derive and
validate the Canadian Syncope Risk Score (CSRS) by enrolling 8176 patients from 11
Canadian EDs in whom no serious condition was identified during the index ED evaluation.
The CSRS was developed conforming to both methodological standards for clinical decision
tool development and reported as per the Transparent Reporting of a Multivariable
Prediction Model for Individual Prognosis or Diagnosis (TRIPOD) guideline. Overall, 9.0%
of patients were hospitalized and 3.6% suffered 30-day serious outcomes after ED
disposition. The CSRS score ranges from -3 to +11. The risk categories were simplified
into low, medium, and high, and the 30-day serious outcomes for each of the three risk
categories. The incidence of arrhythmias in the medium and high-risk groups were 4.9% and
18.0% respectively. Given the importance of occult arrhythmia and uncertainty regarding
the optimal duration of cardiac monitoring, the time interval was analyzed from ED
arrival to arrhythmia detection/intervention or unexplained death, and found that half of
all arrhythmic outcomes were identified within 2 hours among low-risk patients and within
6 hours among medium- and high-risk patients. Furthermore, the more serious, ventricular
arrhythmias occurred only in medium and high-risk patients, and 92% of all arrhythmias
among these risk groups were identified within 15 days. These latencies are highly
relevant to decisions regarding the utility of cardiac monitoring during and after an ED
visit for syncope, with implications for the rational deployment of emerging technology
such as outpatient telemetry which permits real-time identification of serious
arrhythmias. The above inferences regarding cardiac rhythm monitoring are based on the
secondary analysis of observational data. There are no previous randomized controlled
trials (RCTs) that assess the role of outpatient prolonged cardiac monitoring to detect
occult arrhythmias among CSRS medium and high-risk syncope patients discharged from the
ED.
There is a wide variations in ED management, including admission rates (ranging from 5.3%
to 19.6% among sites) and outpatient cardiac testing, very low yield for advanced
neuroimaging, and inefficiencies in hospital admission (among those hospitalized, 46.5%
were for suspected arrhythmias, of whom 71.2% had no cause for syncope identified during
hospitalization. Analyzing our cohort, the study found that CSRS low-risk patients will
benefit the least from hospitalization and CSRS high-risk patients the most. Currently,
21.6% of CSRS medium-risk patients are hospitalized primarily because of concern for
underlying arrhythmia, yet the mortality and the likelihood of identifying an underlying
ventricular arrhythmia within 30 days among these patients is very low. Advances in
ambulatory cardiac rhythm monitoring suggest that this group is an ideal target for
outpatient monitoring, forgoing hospital. admission after ED assessment. A pilot study
was recently with 15-day out-of-hospital live cardiac rhythm monitoring of 72 CSRS medium
and high-risk patients and found that live cardiac monitoring of at-risk ED syncope
patients is feasible, safe, and acceptable.
Hypothesis: the study hypothesizes that a strategy of prolonged outpatient cardiac rhythm
monitoring compared to usual care of at-risk syncope patients, defined as those with CSRS
score ≥3 when discharged from the ED will lead to improved detection of arrhythmias that
require treatment and improve patient safety, healthcare efficiency and patient
satisfaction. What are the principal research questions to be addressed? The overall
objective of this study is to evaluate a strategy of 15-day live cardiac rhythm
monitoring versus usual care to improve the identification of an arrhythmia that required
treatment among at-risk syncope patients discharged from the ED through a patient-level
RCT.
The overall objective of this study is to evaluate a strategy of 15-day live cardiac
rhythm monitoring versus usual care to improve the identification of an arrhythmia that
required treatment among at-risk syncope patients discharged from the ED through a
patient-level RCT.
Trial Design: prospective patient-level multi-center RCT involving 13 participating EDs
across Canada. During the trial period, syncope patients will be block randomized to
usual care or prolonged outpatient cardiac rhythm monitoring in blocks of variable sizes
and stratified by risk scores (3-5, ≥6) and study site.
Patients randomized to usual care will receive all care as prescribed by the discharging
physician and there will be no study-specific interventions. Patients randomized to the
intervention arm will receive 24/7 live cardiac rhythm monitoring for 15 days
(Cardiophone Plus; an external loop recorder). If a patient is randomized to the
intervention arm and is prescribed outpatient cardiac monitoring such as Holter monitor,
this will be replaced by the 24/7 live monitoring and will be applied either prior or
within 24 hours of discharge from the ED. As the intervention arm provides 24/7 live
cardiac monitoring which is a higher level of care than the control arm, there is no
safety risk to the patients in the intervention arm. Cardiophone Plus evaluates all
cardiac beats and rhythm abnormalities that are detected as per the algorithm programmed
into the device. These abnormalities are then automatically and immediately transmitted
to a central monitoring station without the need of any patient intervention
(device-triggered transmission). The central monitoring station is in Windsor, Ontario
(Canadian Cardiac Care) and is staffed round the clock by certified electrocardiographic
technicians and a cardiologist on-call.
Timeline and follow-up: the study timeline is 18 months of patient enrollment and data
collection. The duration of the treatment period for patients in the intervention arm
will receive 15 days of cardiac monitoring. All study patients will be followed at Day 30
either by telephone or email and at 1-year through data linkage with the provincial
health database.
Embedded observational study: validation of the CSRS ultra-low-risk criteria and to
evaluate if the CSRS can be updated to improve its accuracy, ED physician to obtain
verbal consent from patients who are lower risk (score <3) for 30-day follow-up and
addition of cardiac biomarker using the left-over blood at study centers that are able to
accomplish such additional testing for research purposes. These patients will not be
enrolled in the randomized controlled trial.
