Unexplained Syncope: The Importance of the Electrophysiology Study

Syncope of cardiac origin may be associated with an increased risk of sudden cardiac death if not treated in a timely and appropriate manner. The diagnostic approach of syncope imposes a significant economic burden on society. The investigation and elucidation of the pathogenetic mechanism of syncope are of great clinical importance, as both prognosis and appropriate therapeutic approaches depend on these factors. The responsible mechanism of presyncope or syncope can only be revealed through the patient history, baseline clinical examination and electrocardiogram. The percentage of patients who are diagnosed with these tests alone exceeds 50%. In patients with a history of organic or acquired heart disease or/and the presence of abnormal findings on the electrocardiogram, a further diagnostic electrophysiology inclusive approach should be followed to exclude life threatening arrhythmiological mechanism. However, if the patient does not suffer from underlying heart disease and does not show abnormal electrocardiographic findings in the electrocardiogram, then the probability in the electrophysiology study to find a responsible cause is small but not absent. The role of a two-step electrophysiology study inclusive risk stratification approach for the effective management of the former is thoroughly discussed in this review.

Implantable loop recorder follow-up

Introduction Long ambulatory ECG monitoring can be a useful component in the evaluation of the patient with unexplained syncope or syncope with suspected arrhythmic origin, as well as a sensitive tool for detecting asymptomatic spontaneous cardiac arrhythmias or conduction abnormalities in predisposed patients. Purpose To determine the diagnostic cost-effectiveness of the implantable loop recorder (ILR) in the origin of unexplained syncope in our center. Methods A retrospective observational study was carried out in a tertiary center, those patients with an ILR between August 2014 and March 2021 were included. Baseline characteristics of the population and their previous ECG, arrythmias detected during follow-up and pacemaker implant rate were evaluated. Results One hundred twenty-seven patients with a ILR were included (age 67 years, 49.6% males). Most often cause of ILR was unexplained syncope (90.6%) followed by monitoring after TAVI implant (3.9%). Normal LVEF (>50%) was present in 85.6%,and 75.6% had NYHA I functional class. 118 patients (92.9%) presented sinus rhythm at implant time, and 8 (6.3%) presented AF. 12.6% presented first degree atrioventricular (AV) block, 2 patients (1.6%) had presented previously Mobitz Type I AV block and one patient 2:1 block. Left bundle branch block (LBBB) was present in 13.4%,RBBB in 3.1%,LAFB in 9.4%, RBBB+LAFB in 11% and RBBB+LPFB in 2.4%. Median time of follow-up was 21 months. 3rd degree AV block was the most frequent arrhythmia detected (12.1%), followed by >3s pause (8%) and previously unknown AF (2.4%).The patients with syncope who suffered head trauma (33%) presented a higher rate of pacemaker (PCM) implant compared to those without head trauma: 31.6% vs 14.7%. In total,19.8% PCM rate implant during follow-up. No complications ILR related. Conclusion In conclusion, long home ECG monitoring with ILR is a powerful and helpful tool to find out or rule out potentially dangerous arrhythmias as cause of syncope, with no complications in our experience. FUNDunding Acknowledgement Type of funding sources: None. Baseline characteristics Arrhythmias detected during follow-up

Microvolt t-wave alternans its clinical significance in the assessment of the risk of sudden cardiac death among patients with hypertrophic cardiomyopathy

Summary Some patients with hypertrophic cardiomyopathy (HCM) are at significant risk of premature sudden death. Identification of the risk factors may enable effective prevention of adverse cardiac events in these patients. Assessment of the microvolt T-wave alternans (MTWA) is a recognized non-invasive diagnostic test used in risk stratification of sudden cardiac death (SCD). However, the number of reports on the frequency of occurrence of MTWA in HCM is small. Aim: Evaluation of the prognostic value of MTWA in predicting the risk of arrhythmic events (sudden cardiac death, documented VT/VF, appropriate ICD discharge) in patients with HCM. Material and methods 122 patients with HCM underwent detailed clinical assessment and ECG- and echocardiographic examination. They underwent 24-hour ambulatory ECG monitoring, and the following elements were analysed: 1) arrhythmias, 2) heart rate variability (HRV) and the QT segment, 3) the presence of ventricular late potentials (LP), 4) heart rate turbulence (HRT). MTWA assessment was made during a test on a treadmill (Cambridge Heart). In accordance with the adopted criteria, the test was interpreted as negative, positive or indeterminate. Subsequently, positive and indeterminate results were described collectively as MTWA(+) and negative results as MTWA(−). Then the patients were divided into two groups: Group 1 – 57 patients (46,7%) with MTWA(−), and Group 2 – 65 patients (53,2%) with MTWA(+). In order to stratify the risk, the following were adopted as composite primary endpoints: sudden cardiac death or hospitalization for life-threatening arrhythmias (VT/VF), and appropriate ICD discharge. Results The mean follow-up period of the patients was 57±8 months; during that time, events that met the criteria for the endpoint occurred in 16 patients. On the basis of univariate analysis, 10 variables with a significant influence on the occurrence of an event were selected (unexplained syncope, NT-proBNP values elevated above 411 pg/ml, size of the left atrium over 44mm, diastolic thickness of the interventricular septum over 25 mm, the presence of MTWA(+), the QRS width >90 msec, QTc >467 msec, QTd >70 msec, SDNN <110 msec, and sinus rhythm turbulence parameters TS <2,9 ms/2RR). These variables were then included in a multivariate analysis. The model from a Cox regression analysis showed that the presence of unexplained syncope (HR=1,4), MTWA(+) (HR=1,5), size of the left atrium over 44mm (HR=5), and the thickness of the interventricular septum over 25 mm (HR=1,5) increased the risk of sudden events. Conclusions 1) Patients with hypertrophic cardiomyopathy had a significant percentage of positive results of the microvolt T-wave alternans test (MTWA+), 2) Positive MTWA test result in patients with hypertrophic cardiomyopathy can help to identify patients at risk of sudden cardiac death. FUNDunding Acknowledgement Type of funding sources: None.

Atrial fibrillation in unexplained syncope: observations from the Reveal LINQ registry

Background Implantable loop recorders (ILRs) have come to play an important role in the workup of patients with recurrent syncope of uncertain origin. In addition to detecting bradyarrhythmias related to syncope, which is the main diagnostic focus in these patients, ILRs are also capable of uncovering subclinical atrial fibrillation (AF). Purpose We sought to determine the percentage of patients monitored with an ILR for unexplained syncope who have AF detected and to describe clinical actions taken in these patients. Methods Patients enrolled in the Reveal LINQ Registry who received an ILR for unexplained syncope and had at least one follow-up form were included. The device automatically detects AF episodes lasting ≥2 minutes. Patients were considered to have AF based on an AF diagnosis made by the treating physician during follow-up or if device-detected AF was adjudicated as true AF by an external reviewer. AF detection rates were calculated using Kaplan-Meier methods. Results In total, 498 patients (aged 61.8±20.0 years, 49.6% female, CHA2DS2VASc score 2.2±1.7) were included and followed for 22±12 months. A history of AF was present in 97 (20%) patients, while 401 patients had no history. By 18 months, the incidence of AF was 70.9% (95% CI, 60.8%, 80.3%) in patients with a history of AF and 21.4% (95% CI, 17.4%, 26.1%) in patients without (Figure). AF detection in those with (30.4%) and without (30.1%) syncope during follow-up was similar. By the end of follow-up, and among patients with newly detected AF, 29/86 (33.7%) were on oral anticoagulation, 7 (8.1%) underwent AF ablation, 6 (7.0%) underwent other type of ablation, and 2 (2.3%) received cardioversion. Other actions among the whole cohort included implant of an IPG, ICD, or CRT in 98/498 (19.7%). Conclusion Among patients monitored with ILRs to determine the cause of recurrent syncope episodes, approximately 1 in 5 patients had new AF detected. In addition to improving the management of patients with syncope, ILR data served to support AF-related clinical decisions. FUNDunding Acknowledgement Type of funding sources: Private company. Main funding source(s): Medtronic Inc Incidence of AF according to baseline AF

To analyze the clinical characteristics of emergency syncope patients and explore their clinical treatment strategies

Objective To analyze the clinical characteristics of emergency syncope patients and explore the strategies in their clinical treatment. Methods Eighty-five patients with emergency syncope admitted to our hospital from January 2019 to April 2021 were reviewed. The clinical data of all patients were retrospectively analyzed. The common causes were analyzed and summarized, and the strategies in clinical treatment were proposed. Results The main causes of syncope are neuroreflex syncope, follow by cardiac syncope, cerebral syncope, orthostatic hypotension syncope, hysterical syncope and unexplained syncope. They accounted for 35.3%, 30.6%, 15.3%, 12.9%, 3.5%, and 2.4%, respectively. Conclusion Emergency department physicians should evaluate emergency syncope patients in time, identify patients as soon as possible, confirm the etiological diagnosis, and give reasonable and effective symptomatic treatment and treatment measures in order to improve the prognosis and ensure the life safety and quality of patients.

Underlying hemodynamic differences are associated with responses to tilt testing

Aim of this study was to explore whether differences in resting hemodynamic parameters may be associated with tilt test results in unexplained syncope. We analyzed age, gender, systolic (SBP), diastolic blood pressure (DBP) and heart rate (HR) by merging three large databases of patients considered likely to be of vasovagal reflex etiology, comparing patients who had tilt-induced reflex response with those who did not. Tilt-induced reflex response was defined as spontaneous symptom reproduction with characteristic hypotension and bradycardia. Relationship of demographics and baseline supine BP to tilt-test were assessed using logistic regression models. Individual records of 5236 patients (45% males; mean age: 60 ± 22 years; 32% prescribed antihypertensive therapy) were analyzed. Tilt-positive (n = 3129, 60%) vs tilt-negative patients had lower SBP (127.2 ± 17.9 vs 129.7 ± 18.0 mmHg, p < 0.001), DBP (76.2 ± 11.5 vs 77.7 ± 11.7 mmHg, p < 0.001) and HR (68.0 ± 11.5 vs 70.5 ± 12.5 bpm, p < 0.001). In multivariable analyses, tilt-test positivity was independently associated with younger age (Odds ratio (OR) per 10 years:1.04; 95% confidence interval (CI), 1.01–1.07, p = 0.014), SBP ≤ 128 mmHg (OR:1.27; 95%CI, 1.11–1.44, p < 0.001), HR ≤ 69 bpm (OR:1.32; 95%CI, 1.17–1.50, p < 0.001), and absence of hypertension (OR:1.58; 95%CI, 1.38–1.81, p < 0.001). In conclusion, among patients with suspected reflex syncope, younger age, lower blood pressure and lower heart rate are associated with positive tilt-test result.

Risk of incident fractures in individuals hospitalised due to unexplained syncope and orthostatic hypotension

Background Impaired orthostatic blood pressure response and syncope confer a high risk of falls and trauma. The relationship between a history of unexplained syncope and orthostatic hypotension (OH) with subsequent fractures, however, has not been thoroughly examined. In this study, we aimed to investigate the relationship between previous hospital admissions due to unexplained syncope and OH and incident fractures in a middle-aged population. Methods We analysed a large population-based prospective cohort of 30,399 middle-aged individuals (age, 57.5 ± 7.6; women, 60.2%). We included individuals hospitalised due to unexplained syncope or OH as the main diagnosis. Multivariable-adjusted Cox regression analysis was applied to assess the impact of unexplained syncope and OH hospitalisations on subsequent incident fractures. Results During a follow-up period of 17.8 + 6.5 years, 8201 (27%) subjects suffered incident fractures. The mean time from baseline and first admission for syncope (n = 493) or OH (n = 406) was 12.6 ± 4.2 years, and the mean age of the first hospitalisation was 74.6 ± 7.4 years. Individuals with incident fractures were older, more likely to be women, and had lower BMI, higher prevalence of prevalent fractures, and family history of fractures. Multivariable-adjusted Cox regression showed an increased risk of incident fractures following hospitalisations due to unexplained syncope (HR 1.20; 95% CI 1.02–1.40; p = 0.025) and OH (HR 1.42; 95% CI 1.21–1.66; p < 0.001) compared with unaffected individuals. Conclusions Individuals hospitalised due to unexplained syncope and orthostatic hypotension have an increased risk of subsequent fractures. Our findings suggest that such individuals should be clinically assessed for their syncope aetiology, with preventative measures aimed at fall and fracture risk assessment and management.