Unexplained Syncope Research Articles

Sudden cardiac death in childhood RASopathy-associated hypertrophic cardiomyopathy: validation of HCM Risk-Kids model and predictors of events

Abstract RASopathies represent an important proportion of hypertrophic cardiomyopathy (HCM) cases presenting in childhood. Despite this, there are no published risk factors for sudden cardiac death (SCD) in this cohort of patients. Our primary aim was to validate the HCM Risk-Kids model in children with RASopathy-associated HCM and to investigate additional predictors of SCD in a cohort of 169 patients from 15 international paediatric cardiology centres (UK, Ireland and Germany). Eleven (6.5%) patients experienced a SCD equivalent event [5 (45.5%) an aborted cardiac arrest; 3 (27.3%) SCD; 2 (18.2%) sustained ventricular tachycardia (VT); and 1 (9.1%) appropriate implantable cardioverter-defibrillator (ICD) shock] at a median age of 12.5 months (IQR 7.7-28.64). The calculated SCD equivalent event incidence was 0.78 (95% CI 0.43 – 1.41) per 100 patient years. Six patients (54.54%) with a SCD equivalent event were in the low-risk category according to the HCM Risk-Kids model. Harrell’s C index was 0.5959 (95% CI 0.26-1.22) with a sensitivity of 9.09%, specificity of 63.92%, positive predictive value of 1.72%, and negative predictive value of 90.99%; there was poor distinction between the different risk groups. Unexplained syncope (HR 102.63 (95% CI 14.94 – 704.99), p<0.001) and non-sustained VT [NSVT (HR 5.67 (95% CI 1.30 – 24.70), p=0.021)] were independent predictors of SCD. The HCM Risk-Kids model should not be used for patients with RASopathy-associated HCM but NSVT and unexplained syncope appear to be predictors of SCD in this population. Larger multicentre collaborative studies are required to further investigate predictors of SCD in this group of patients.

Non-invasive estimation of left ventricular systolic peak-pressure: a prerequisite to calculate of myocardial work in hypertrophic obstructive cardiomyopathy

Abstract Introduction Myocardial work (MW) is an echocardiographic parameter to estimate global and regional myocardial performance. This method utilizes pressure strain loops derived from global longitudinal strain (GLS) and left ventricular systolic pressure (LVSP) estimated by brachial blood pressure (BP). Purpose Since LVSP cannot be equated with BP in pts with HOCM, we investigated whether the LVSP can be calculated non-invasively by combining Doppler echo parameters and the BP. This estimation is mandatory to make MW applicable for HOCM-pts. Methods We studied 20 consecutive pts (8 women, 12 men; mean age 57.0±13.9 years; NYHA class 2.1±0.8) with indication for first alcohol septal ablation. 6 pts had hypertension and 2 pts unexplained syncope. 18 (90%) pts were in sinus rhythm. NTproBNP was 1431 pg/ml (1912 IQR). Echo baseline measurements showed subaortic septal (IVS) thickness of 21.0±5.0 mm and maximal IVS thickness of 24.7±6.3 mm. Pts showed high-normal left ventricular ejection fraction (70.4±10.1%). Left atrial (LA) volume was 101.2±26 ml. All measurements of pressures and gradients were performed in the catheterization laboratory after placement of a 5F Judkins JR4 in the ascending aorta and a 5.2F special pigtail catheter in the apex of LV beyond the obstruction. Simultaneous measurements of BP at left upper arm, echo intraventricular gradients (instantaneous and mean) with CW Doppler (GE Vivid E70), and invasive pressures and gradients (peak-to-peak and mean) of the LV and ascending aorta were performed. Echo and invasive gradients were averaged over 3 cardiac cycles. Finally, we tried to identify an estimation of invasively measured LV systolic pressure by combining systolic BP and echo measured gradients. Results Systolic BP was 143±21 mmHg. Max. CW Doppler gradient was 65±29 mmHg and mean gradient was 31±14 mmHg. Invasive simultaneous measurements at rest showed peak-to-peak gradient of 55±24 mmHg and mean gradient of 34±13 mmHg between apical LV and ascending aorta. Mean LVSP was 190±40 mmHg. Systolic pressure of the ascending aorta was 134±28 mmHg. Adding systolic peripheral BP and maximal echo-gradient mean value was 208±38 mmHg. Adding systolic peripheral BP and echo-mean gradient mean value was 174±26 mmHg. Correlating these values with the invasively measured systolic LV pressure we found a slightly higher correlation of the sum of systolic BP and mean-echo gradient (Pearson correlation coefficient: 0.867 p<0.001) compared with the sum of systolic BP and maximal echo-gradient (Pearson correlation coefficient: 0.851; p<0.001). Bland–Altman plots demonstrated good levels of agreements between invasively measured LVSP and both non-invasively estimated LVSP. Conclusions Non-invasive estimation of LVSP is feasible by combining conventional BP and CW Doppler measured mean LV outflow tract gradient in HOCM. Hereby estimation of MW in pts with HOCM is applicable.

A large, real-world cohort analysis of arrhythmia detections with insertable cardiac monitors

Abstract Background Insertable cardiac monitors (ICMs) provide long-term continuous monitoring for arrhythmia diagnosis and management for various clinical indications. However, little data exists on the real-world diagnostic yield of ICMs across indicated patient populations, including both expected and incidental arrhythmic findings. Validated artificial intelligence (AI) algorithms have been developed to identify true arrhythmia episodes while significantly reducing false positives, enabling the adjudication of ICM episodes for larger cohorts of patients. Purpose To characterize comprehensive true arrhythmia detection rates in a large real-world population with long-term ICM monitoring. Methods De-identified patients ≥18 years receiving a Reveal LINQ ICM between Oct 1, 2016 – Sept 30, 2020 with no prior cardiac implantable electronic devices and ≥1 year of follow-up in the CareLink monitoring database were identified (N=12,013). Patients were stratified by reason for ICM placement: N=9,841 who received ICM for diagnosis of suspected arrhythmias (40.8% unexplained syncope, 38.3% cryptogenic stroke, 9.7% palpitations, 9.7% suspected atrial fibrillation (AF), 1.6% ventricular tachycardia), and N=2,172 who received ICM for management of known AF. Device-detected ECGs during long-term follow-up were identified and processed through previously validated arrhythmia-specific AI algorithms designed to reduce false positive arrhythmia detections (each trained using ICM data from ≥25,000 adjudicated ECG episodes and validated on an independent set of ≥5,000 adjudicated ECGs). Results Mean (SD) and median follow-up were 24.6(12.7) and 24.5 months, respectively. In patients receiving ICM for Suspected Arrhythmia, 5,492 patients (55.8%) had ≥1 AI-adjudicated arrhythmia detected during follow-up, with 2,472 (45.0%) of these patients having ≥2 arrhythmia types detected (Table). Mean (SD) time to 1st arrhythmia detection was 7.7(9.1) months; time to 2nd arrhythmia type detected was 12.3(10.4) months. Among the 6,958 patients with longer-term ICM follow-up ≥2 years, 2,931 (42.1%) had no arrhythmias detected (i.e., arrhythmia rule-out occurred). In patients receiving ICM for AF Management, 1,737 patients (80.0%) had ≥1 arrhythmia detected, and notably 1,074 (61.8%) of these patients had ≥1 arrhythmia detected during follow-up that was not AF. Mean (SD) time to 1st arrhythmia detection was 5.3 (7.7) months; time to 2nd arrhythmia type detected was 10.4(9.9) months. Conclusions In a large real-world ICM population, >50% of patients had AI-adjudicated arrhythmia detections during long-term follow-up, with a significant proportion receiving additional arrhythmia diagnoses beyond the initial type diagnosed or suspected. These results suggest that in indicated patients, long-term continuous monitoring with ICMs can enable diagnosis of a variety of cardiac arrhythmias that may have otherwise remained undetected.

The challenge of risk stratification in hypertrophic cardiomyopathy: clinical, genetic and imaging insights from a quaternary referral centre

Abstract Background Hypertrophic cardiomyopathy (HCM) is the commonest genetic cardiomyopathy and may result in sudden cardiac death (SCD). Clinical risk stratification scores are utilised to estimate SCD risk and determine potential utility of a primary prevention implantable cardioverter defibrillator (ICD). Methods Patients with a confirmed diagnosis of HCM from a quaternary HCM service were defined according to clinical characteristics, genetic profiles and cardiac imaging results. European Risk-SCD score and American Heart Association / American College of Cardiology (AHA/ACC) Score were calculated. The primary outcome was cardiac arrest. Results 380 patients with HCM were followed up for a median of 6.4 years. 18 patients (4.7%) experienced cardiac arrest, with predictive factors being younger age (37.2 vs 54.4 years, p=0.0041), unexplained syncope (33.3% vs 9.4%, p=0.007), non-sustained ventricular tachycardia (50.0% vs 12.7%, p<0.0001), increased septal thickness (21.5 vs 17.5mm, p=0.0003), and presence of a sarcomeric gene mutation (100.0% vs 65.8%, p=0.038). The Risk-SCD and AHA/ACC scores had poor agreement (kappa coefficient 0.38). Risk-SCD score had poor sensitivity (44.4%), classifying 55.6% of patients with cardiac arrest as low-risk but was highly specific (93.7%). AHA/ACC risk score did not discriminate between groups significantly. 20 patients (5.3%) died, with most >60-year-olds having a non-cardiac cause of death (p=0.0223). Conclusion This study highlights limited (38%) agreement between the Risk-SCD and AHA/ACC scores. Most cardiac arrests occurred in ostensibly low or medium-risk patients under both scores. Appropriate ICD selection remains challenging. Utilising newer markers such as cardiac MRI and genetic findings may assist future risk refinement.

Implantable loop recorder monitoring in inherited cardiomyopathies: yield of clinically relevant arrhythmias

Abstract Background Implantable loop recorders (ILRs) are a minimally invasive tool for the diagnosis of arrhythmias in patients with unexplained syncope or asymptomatic arrhythmias. Their use in patients with inherited arrhythmia syndromes has been recommended in the recent 2022 ESC Guidelines (1). However, the clinical utility of ILRs in patients with inherited cardiomyopathies remains unexplored. Purpose The purpose of this study was to evaluate the yield of ILR monitoring in detecting clinically relevant events in a single cohort of patients with inherited cardiomyopathies. Methods We prospectively collected demographic, clinical, and follow-up data from patients with inherited cardiomyopathies (Arrhythmogenic Cardiomyopathy, ACM; Hypertrophic Cardiomyopathy, HCM; Dilated Cardiomyopathy, DCM; Left Ventricular Non-Compaction, LVNC) who were implanted with an ILR and were followed with telemedicine. The primary endpoint was a clinically significant event recorded with the ILR that required an update to an implantable cardioverter defibrillator (ICD). Results The study cohort included 53 consecutive patients (55% males; mean age at ILR implantation 35±14 years) with inherited cardiomyopathies: 33/53 (62%) with ACM, 9/53 (17%) with HCM, 7/53 (13%) LVNC, 4/33 (8%) DCM. None of the patients implanted had previously experienced life-threatening arrhythmias. During a median follow-up of 2.6 years (IQR 1.4-3.7 years) after ILR implantation, clinically relevant arrhythmic events were documented in 9/53 (17%) of patients. Specifically, sustained or non-sustained ventricular tachycardia episodes were detected in 8 patients (5 with ACM, 2 with LVNC, 1 with LMNA-related DCM), whereas one patient with HCM showed symptomatic pauses > 3 seconds due to sick sinus syndrome. In all cases, the detection of such episodes led to the upgrade to ICD implantation. Conclusions ILR monitoring of patients with inherited cardiomyopathies identified clinically relevant events in almost one-fifth of patients, suggesting that the use of ILR may substantially improve the management of these patients. Figure 1. Representative example of clinically actionable event detected by implantable loop recorder (ILR) in a patient with inherited cardiomyopathy. The patient, a 19-year-old male with a definitive diagnosis of Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) and a pathogenic PKP2 truncating variant, presented with palpitations and vertigo during physical exertion one year after the implantation of an ILR. ILR monitoring documented a rapid tachycardia with a mean frequency of 250 bpm lasting 3 minutes, prompting an indication for an implantable cardioverter defibrillator (ICD).Figure 1.

Head-up tilt test induced asystole and recurrent syncope: a follow-up study

Abstract Introduction Head-up tilt test (HUTT) is a valuable diagnostic tool in unexplained and recurrent syncope, especially when reflex etiology is suspected. If asystole is the dominant feature of reflex syncope, permanent pacemaker therapy may be effective for reducing syncope recurrence. Purpose To investigate syncope recurrence, pacemaker implantation and death of patients with syncope and asystole induced by HUTT and carotid sinus message (CSM). Methods Retrospective analysis of consecutive patients referred for HUTT between January 2017 and December 2021 and selection of those with cardioinhibitory response, defined by syncope or pre-syncope and asystolic pause ≥3 seconds. Patients’ follow-up (FUP) was performed via a phone interview and analysis of clinical records, to assess recurrence of syncope, treatments, and death. Results A total of 44 patients were included: 30 (68,2%) were men, with a median age of 69 years (interquartile range (IQR) of 24). Asystole was experienced after CSMin 41 patients and during tilt test alone in 3 patients. Median FUP was 26 months (IQR 23). There were 19 (44,2%) patients who implanted pacemaker (PM), all with cardioinhibitory carotid sinus syndrome ( I-CSS), 57,9% men, with median age of 74 years (IQR 19) and median duration of asystole during CSMof 6,3 seconds (IQR 3,8). Of these, 5 (26,3%) implanted a unicameral PM and the remaininga bicameral PM, with AAI-DDD mode programming. Two patients had PM-related complications: infection and dislodgment of ventricular lead, both in the first 15 days after implantation. Median atrial and ventricular pacing percentage at last PM consultation was 7% (IQR 28) and 1% (IQR 4), respectively. There was a positive strong correlation between the percentage of atrial pacing at first and at last appointment (p<0,001, r=0,867) and a positive moderated correlation between the percentage of ventricular pacingat first and at last appointment (p=0,022, r=0,586), suggesting a similar degree of pacing along FUP-time. Only three patients (6,8%) had syncope recurrence, all men with CI-CSS, median age of 78; one patient had syncope before implantation PM, other relapsed 2-times with a PMimplanted and the third refused PMimplantation despite 5-time recurrence of symptoms. There was no association between the duration of the asystole during HUTT with implantation of PM nor syncope recurrence (p>0.2). Age at HUTT was significantly associated both with CI-CSS and PM implantation (p=0,001 and p=0,045, respectively). Two patients died, both of oncologic causes. Conclusion In agreement with the literature, our cohort of patients with cardioinhibitory response during HUTT and CSM experienced an overall good prognosis, with no cardiac deaths; there was very low syncope recurrence, not allowing a comparison between the groups with and without pacemaker. Age at HUTT was significantly associated both with CI-CSS and PMimplantation.

Haemodynamic Responses and Effectiveness of Head Upright Tilt Test in Unexplained Syncope in Children

Haemodynamic Responses and Effectiveness of Head Upright Tilt Test in Unexplained Syncope in Children

Remote monitoring of implantable cardiac monitors in patients with unexplained syncope: Predictors of false-positive alert episodes.

Remote monitoring is recommended for patients with implantable cardiac monitors (ICMs), but compared to other cardiac implantable devices, ICMs are less accurate and transmit a higher number of alerts. The aim of this study was to investigate the predictors of false-positive (FP) arrhythmic alerts in patients with unexplained syncope who were implanted with ICM and followed by an automatic remote monitoring system. We retrospectively evaluated all consecutive patients who received a long-sensing vector ICM for unexplained syncope between January 2019 to September 2021 at our Syncope Unit. The primary endpoint was the incidence of the first FP episode. The secondary endpoints included assessing the incidence of FP episodes for all types of algorhythms and indentifying the reasons for the misdetection of these episodes. Among 105 patients (44.8% males, median age 51 years), 51 (48.6%) transmitted at least one FP alert during a median follow-up of 301 days. The presence of pre-ventricular complexes (PVCs) on the resting electrocardiogram was the only clinical characteristic associated with an increased risk of FP alerts (adjusted Hazard ratio [HR] 5.76 [2.66-12.4], p=0.010). The other significant device-related variables were a low-frequency filter at 0.05Hz versus the default 0.5Hz (adjusted HR 3.82 [1.38-10.5], p=0.010) and the R-wave amplitude (adjusted HR 0.35 [0.13-0.99], p=0.049). Patients who have PVCs are at higher risk of inappropriate ICM activations. To reduce the occurrence of FP alerts, it may be beneficial to target a large R-wave amplitude during device insertion and avoid programming a low-frequency filter at 0.05Hz.

Tilt table testing, methodology and practical insights for the clinic.

Tilt table testing (TTT) has been used for decades to study short-term blood pressure (BP) and heart rate regulation during orthostatic challenges. TTT provokes vasovagal reflex in many syncope patients as a background of widespread use. Despite the availability of evidence-based practice syncope guidelines, proper application and interpretation of TTT in the day-to-day care of syncope patients remain challenging. In this review, we offer practical information on what is needed to perform TTT, how results should be interpreted including the Vasovagal Syncope International Study classification, why syncope induction on TTT is necessary in patients with unexplained syncope and on indications for TTT in syncope patient care. The minimum requirements to perform TTT are a tilt table with an appropriate tilt-down time, a continuous beat-to-beat BP monitor with at least three electrocardiogram leads and trained staff. We emphasize that TTT remains a valuable asset that adds to history building but cannot replace it, and highlight the importance of recognition when TTT is abnormal even without syncope. Acknowledgement by the patient/eyewitness of the reproducibility of the induced attack is mandatory in concluding a diagnosis. TTT may be indicated when the initial syncope evaluation does not yield a certain, highly likely, or possible diagnosis, but raises clinical suspicion of (1) reflex syncope, (2) orthostatic hypotension (OH), (3) postural orthostatic tachycardia syndrome or (4) psychogenic pseudosyncope. A therapeutic indication for TTT in the patient with a certain, highly likely or possible diagnosis of reflex syncope, may be to educate patients on prodromes. In patients with reflex syncope with OH TTT can be therapeutic to recognize hypotensive symptoms causing near-syncope to perform physical countermanoeuvres for syncope prevention (biofeedback). Detection of hypotensive susceptibility requiring therapy is of special value.

Identification of acute ST-elevation myocardial infarction via remote implantable loop recorder monitor

The indications for the use of implantable loop recorders include the evaluation of unexplained palpitations and syncope, embolic stroke of undetermined source, dizziness and lightheadedness presumed to be due to arrhythmogenic etiology, and for atrial fibrillation to guide antiarrhythmic drug therapy or catheter ablation efficacy. Long-term monitoring is especially beneficial if symptoms occur sporadically or are asymptomatic in nature. This is the first case to our knowledge of an acute ST-elevation myocardial infarction which was identified from remote monitoring of an implantable loop recorder through a device clinic.

The challenge of risk stratification in hypertrophic cardiomyopathy: Clinical, genetic and imaging insights from a quaternary referral centre

BackgroundHypertrophic cardiomyopathy (HCM) is the commonest genetic cardiomyopathy and may result in sudden cardiac death (SCD). Clinical risk stratification scores are utilised to estimate SCD risk and determine potential utility of a primary prevention implantable cardioverter defibrillator (ICD). MethodsPatients with a confirmed diagnosis of HCM from a quaternary HCM service were defined according to clinical characteristics, genetic profiles and cardiac imaging results. European Risk-SCD score and American Heart Association / American College of Cardiology (AHA/ACC) Score were calculated. The primary outcome was cardiac arrest. Results380 patients with HCM were followed up for a median of 6.4 years. 18 patients (4.7%) experienced cardiac arrest, with predictive factors being younger age (37.2 vs 54.4 years, p = 0.0041), unexplained syncope (33.3% vs 9.4%, p = 0.007), non-sustained ventricular tachycardia (50.0% vs 12.7%, p < 0.0001), increased septal thickness (21.5 vs 17.5 mm, p = 0.0003), and presence of a sarcomeric gene mutation (100.0% vs 65.8%, p = 0.038). The Risk-SCD and AHA/ACC scores had poor agreement (kappa coefficient 0.38). Risk-SCD score had poor sensitivity (44.4%), classifying 55.6% of patients with cardiac arrest as low-risk but was highly specific (93.7%). AHA/ACC risk score did not discriminate between groups significantly. 20 patients (5.3%) died, with most >60-year-olds having a non-cardiac cause of death (p = 0.0223). ConclusionThis study highlights limited (38%) agreement between the Risk-SCD and AHA/ACC scores. Most cardiac arrests occurred in ostensibly low or medium-risk patients under both scores. Appropriate ICD selection remains challenging. Incorporating newer risk markers such as HCM genotyping and myocardial fibrosis quantification by cardiac MRI may assist future risk refinement.

Sudden cardiac death in childhood RASopathy-associated hypertrophic cardiomyopathy: Validation of the HCM risk-kids model and predictors of events

BackgroundRASopathies account for nearly 20% of cases of childhood hypertrophic cardiomyopathy (HCM). Sudden cardiac death (SCD) occurs in patients with RASopathy-associated HCM, but the risk factors for SCD have not been systematically evaluated. AimTo validate the HCM Risk-Kids SCD risk prediction model in children with RASopathy-associated HCM and investigate potential specific SCD predictors in this population. MethodsValidation of HCM Risk-Kids was performed in a retrospective cohort of 169 patients with a RASopathy-associated HCM from 15 international paediatric cardiology centres. Multiple imputation by chained equations was used for missing values related to the HCM Risk-Kids parameters. ResultsEleven patients (6.5%) experienced a SCD or equivalent event at a median age of 12.5 months (IQR 7.7–28.64). The calculated SCD/equivalent event incidence was 0.78 (95% CI 0.43–1.41) per 100 patient years. Six patients (54.54%) with an event were in the low-risk category according to the HCM Risk-Kids model. Harrell's C index was 0.60, with a sensitivity of 9.09%, specificity of 63.92%, positive predictive value of 1.72%, and negative predictive value of 91%; with a poor distinction between the different risk groups. Unexplained syncope (HR 42.17, 95% CI 10.49–169.56, p < 0.001) and non-sustained ventricular tachycardia (HR 5.48, 95% CI 1.58–19.03, p < 0.007) were predictors of SCD on univariate analysis. ConclusionUnexplained syncope and the presence of NSVT emerge as predictors for SCD in children with RASopathy-associated HCM. The HCM Risk-Kids model may not be appropriate to use in this population, but larger multicentre collaborative studies are required to investigate this further.

Definitive aetiology of unexplained syncope after cardiovascular autonomic tests in a tertiary syncope unit.

Syncope is a common condition with many possible causes, ranging from benign to life-threatening aetiologies. Establishing a diagnosis can be difficult, and specialized syncope units, using cardiovascular autonomic tests (CATs), including a head-up tilt test, can increase the diagnostic yield. However, up to one-fifth of examined patients have inconclusive CAT results. The aim of the present study was to investigate the predictive value of history, and clinical findings for unexplained syncope after CAT and characterize the group with negative results. Consecutive syncope patients [n = 2663, 61% women, median age 52 (32-69) years] were evaluated and CAT explained aetiology of syncope in 79% of cases, whereas 21% remained unexplained. Predictors of negative CAT were older age at first syncope (+8% higher odds per 10-year increment, P = 0.042), higher supine heart rate (HR; +12% per 10 b.p.m.; P = 0.003), absence of prodromes (+48%; P < 0.001), hypertension (+45%; P = 0.003), diabetes (+82%; P < 0.001), heart failure (+98%; P = 0.014), and coronary artery disease (+51%; P = 0.027). Compared with vasovagal syncope, patients with negative CAT were older, reported more often the absence of prodromes, and had a higher burden of cardiovascular comorbidities. A cardiovascular autonomic test established the cause of syncope in 79% of patients evaluated in a syncope unit. Syncope without prodromes and cardiovascular comorbidities were significant predictors of failure to reveal an aetiology from assessment by CAT. These are known risk factors for cardiac syncope and patients with inconclusive CAT warrant further investigation.

Heart Rate Variability in Unexplained Syncope Patients Versus Healthy Controls: A Comparative Study.

Background Syncope or fainting is the sudden and transient loss of consciousness. This could lead to an increase in mortality due to sudden cardiac death or comorbidity in these patients. Heart rate variability (HRV) is a noninvasive bedside procedure for assessing the cardiovascular autonomic function. There may be an abnormal alteration in the HRV parameters in syncope patients. This can be used for looking into cardiovascular autonomic changes in syncope. This would help in early diagnosis and intervention. Objective The aim of this present study was to compare the HRV parameters betweenunexplained syncope patients andage-matched healthy controls and to find a correlation between HRV parameters and cardiovascular parameters like pulse and mean blood pressure. Materials and methods A five-minute continuous electrocardiogram (ECG) was recorded and HRV analysis was done by ADInstruments' PowerLab (Oxford, United Kingdom) for 25 cases and 25 controls. Results The mean standard deviation of the RR interval (SDRR) in millisecondswas found to be significantly lower in the cases (21.93 ± 3.53) as compared to controls (71.27 ± 27.40). The mean value of the low-frequency to high-frequency ratio (LF/HF) was significantly higher in cases (1.43 ± 0.40) as compared to controls (0.98 ± 1.07). However, there was no significant correlation between the pulse, blood pressure, and HRV measures. Conclusion The findings suggest a sympathetic predominance in the cases of unexplained syncope as compared to the controls.

Remote monitoring of implantable loop recorders reduces time to diagnosis in patients with unexplained syncope: a multicenter propensity score-matched study.

There are little data on remote monitoring (RM) of implantable loop recorders (ILRs) in patients with unexplained syncope and whether it confers enhanced diagnostic power. To evaluate the effect of RM in ILR recipients for unexplained syncope for early detection of clinically relevant arrhythmias by comparison with a historical cohort with no RM. SyncRM is a propensity score (PS)-matched study prospectively including 133 consecutive patients with unexplained syncope and ILR followed up by RM (RM-ON group). A historical cohort of 108 consecutive ILR patients with biannual in-hospital follow-up visits was used as control group (RM-OFF group). The primary endpoint was the time to the clinician's evaluation of clinically relevant arrhythmias (types 1, 2, and 4 of the ISSUE classification). The primary endpoint of arrhythmia evaluation was reached in 38 patients (28.6%) of the RM-ON group after a median time of 46 days (interquartile range, 13-106) and in 22 patients (20.4%) of the RM-OFF group after 92 days (25-368). The PS-matched adjusted ratio of rates of arrhythmia evaluation was 2.53 (95% confidence interval, 1.32-4.86) in the RM-ON vs. RM-OFF group (p = 0.005). In our PS-matched comparison with a historical cohort, RM of ILR patients with unexplained syncope was associated with a 2.5-fold higher chance of evaluations of clinically relevant arrhythmias as compared with biannual in-office follow-up visits.

Detection rate and shunt grading with synchronous testing of contrast transcranial Doppler and contrast transthoracic echocardiography: Preliminary findings.

Patent foramen ovale, a common congenital atrial septal defect, may lead to cardiac right-to-left shunting (RLS), which has been associated with various diseases. Reliable techniques for detecting RLS are essential for diagnosis and assist with treatment decision-making. Contrast transcranial Doppler (c-TCD), contrast transthoracic echocardiography (c-TTE), and contrast transesophageal echocardiography can be used to detect RLS. However, it is still unclear which ultrasound modalities are the most practical and cost-effective. To evaluate the efficacy of synchronous c-TCD and c-TTE in detecting cardiac RLS. We prospectively designed and continuously recruited 100 patients with cryptogenic stroke, migraines, transient ischemic attack, unexplained syncope, or dizziness admitted at the First Affiliated Hospital of Shenzhen University between February 2020 and August 2020. Ninety-five patients underwent synchronous c-TCD and c-TTE (during a single contrast-enhanced ultrasound session). We compared synchronous test results with the results of c-TCD alone and c-TTE alone. Ninety-five patients successfully underwent synchronous c-TCD and c-TTE, with the data analyzed for each individual. The positive detection rates of Grade I, II, and III shunts with synchronous c-TCD and c-TTE were higher than those with c-TTE or c-TCD alone (P = .047, P = .002, and P = .024, respectively). Overall, the positive detection rates of synchronous tests, c-TCD alone, and c-TTE were 69.5%, 51.6%, and 31.6%, respectively (P = .000, and P = .012). Among the 66 patients who were double-RLS-positive (both c-TTE and c-TCD showed positive results), as detected by the synchronous test, 26 (39.3%) patients who underwent c-TTE alone had higher shunt grades detected than those who underwent c-TCD alone. Conversely, 5 (7.6%) patients who underwent c-TCD alone had higher shunt grades detected than those who underwent c-TTE alone (P = .000). Synchronous c-TCD and c-TTE testing can significantly improve the detection rate, accuracy, and test process efficacy for quantifying RLS, and reduce the testing risk, workload, and medical costs.

Abnormal origin of the left coronary artery

A 31-year-old female with a medical history of unexplained syncope presented with atypical chest pain. The patient has a healthy lifestyle and no risk factors.

Pharmacological inducibility of short-coupled Purkinje ectopy in patients with spontaneous short-coupled ventricular fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Introduction In a subset of patients with idiopathic ventricular fibrillation (IVF), the cause is identified as short-coupled premature ventricular complexes (ScPVCs), which mostly originate from Purkinje cells, and are often short-living and undetected. There is no consistent test allowing identification of patients vulnerable to this malignant arrhythmia. We aimed at evaluating sodium channel blocker (NaBl) testing in patients who survived IVF associated with SCPVCs. Methods We retrospectively reviewed data of 112 patients at 3 centers, with the diagnosis of IVF associated with spontaneous and documented scPVCs. No patient from the previous report was included. We analyzed all patients who underwent NaBl tests during evaluation of IVF. An arrhythmogenic NaB test was defined as the occurrence of ≥10 scPVCs and/or ≥ 1 repetitive form (couplet, triplet, run) during the test, without spontaneous scPVC at baseline. We defined scPVCs as an R-on-T pattern PVC. We evaluated the occurrence of scPVC during NaB infusion, the arrhythmia pattern and we compared the characteristics of the arrhythmogenic versus non-arrhythmogenic response groups. Data regarding anti-arrhythmic drug treatment and follow-up were collected at each center. Results In total, 48 patients were included (Table). The NaB tests were performed using ajmaline 1mg/kg/5 or 10min, or flecainide 2mg/kg/10min. Overall, an arrhythmogenic NaB test occurred in 23 of 48 (48%) patients. Isolated ScPVCs were observed in 11 patients, couplet/triplets in 10, and runs in 6. The arrhythmogenic response was reproduced in 5/5 patients who had a second NaB test during scPVC mapping before catheter ablation. There were no significant differences between patients with arrhythmogenic or non-arrhythmogenic NaB tests in all baseline clinical variables tested including VF burden (Table). All patients were followed at least 1 year after initial diagnosis and NaB test. Under hydroquinidine (600 or 900mg/day), appropriate defibrillator shocks occurred in 7 of 8 patients with arrhythmogenic NaB test; whereas shocks occurred only in 2 of 11 patients with non-arrhythmogenic NaB test (P=0.02). Conclusion Sodium blockers unravel scPVCs in up to 50% of patients with IVF and may therefore represent a valuable tool to detect a potential cause for sudden cardiac death (SCD) or unexplained syncope. Additionally, the arrhythmogenic response to NaB may be associated with the success of hydroquinidine in preventing IVF recurrence, a finding that suggests the existence of distinct scPVCs phenotypes and that may have important therapeutic implications. Further functional and genetical investigations are warranted to explore the mechanisms underlying this association.

Implantable cardioverter-defibrillator implantation should be considered in high-risk patients with apical hypertrophic cardiomyopathy as the same manner with the septal type

Abstract Funding Acknowledgements Type of funding sources: None. Background Apical hypertrophic cardiomyopathy (HCM) is considered to have a benign prognosis in terms of cardiovascular mortality. Sudden cardiac arrest and ventricular fibrillation (VF) in patients with apical HCM is rarely reported. Methods Between July 2001 and May 2021, 96 HCM patients who had undergone implantable cardioverter-defibrillator (ICD) implantation from three tertiary hospitals were reviewed. We evaluated the prevalence of aborted sudden cardiac death and/or documented VF in apical HCM and known risk markers for sudden cardiac death in those populations. Result Fifteen patients (15.6%) were apical HCM in total population. Among apical HCM, seven patients (40.0%) presented with aborted sudden cardiac death or documented VF, therefore received ICD implantation for the secondary prevention. All seven patients had at least one risk marker suggested either 2020 ACC/AHA guideline or 2014 ESC guideline. One patient had three risk factors and two patients had two risk factors and four patients had one risk factor. Late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR), personal history of unexplained syncope and non-sustained ventricular tachycardia (VT) were the common risk factors. Conclusions Clinical outcomes in patients with apical HCM are not always as benign as previously thought. ICD implantation should be considered in high-risk patients with apical HCM as the same manner with the septal type of HCM according to the current guideline recommendations.

Optimization of the clinical workflow and patient pathway in cardiac monitor implantation and follow-up

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Medtronic Background Clinical evidence supports the use of Insertable Cardiac Monitors (ICMs) to determine the aetiology of recurrent unexplained syncope and cryptogenic stroke. ICMs continuously monitor cardiac arrhythmias, enabling appropriate diagnosis and treatment. A remote follow-up system transfers ICM data to hospital staff for analysis. This creates a significant data-burden for the staff. Purpose To assess the impact of efficiency optimization of the diagnostic patient pathway and clinical workflow for patients eligible for an ICM. Methods We collected patient-level data from all patients that received an ICM at a university hospital in 2018 and 2020 to assess the change in the clinical workflow with one year follow-up time. Pathway improvements included moving the procedure out of the catheterization lab (cath lab), switching to a nurse-led pathway as well as outsourcing part of the remote follow-up workflow to an external monitoring centre. Results The number of implanted ICMs doubled from 74 in 2018 to 159 in 2020. In 2018, all implantations were done by a physician while in 2020, 70 % were done by nurses. In 2018 the operation schedule was 60 min for an ICM, compared to 45 minutes in 2020. The waiting time from referral to implantation was significantly shorter in 2020 (mean=36 days) compared to 2018 (mean=49 days), p=0,008. Implantations done in the cath lab decreased significantly (19 % in 2018; 2 % in 2020). Patients receiving an ICM after syncope increased from 71 to 94 patients. Stroke and transient ischemic attack (TIA) as an implantation indication increased substantially from 2018 to 2020 (2 and 62 patients, respectively). In 2018, nurses analysed all remote transmissions. In 2020 the first line review and triaging of remote transmissions was outsourced to an external monitoring and triaging centre. This external service escalated only 11 % of the transmissions (204 out of 1817) to the clinic for revision. Under the assumption that a nurse uses 11 minutes per transmission as seen in previous studies, this saved 296 hours of nursing time in 2020. The nurse-led implantation in 2020 saved 48 hours of physicians’ time compared to what would have been used by the process in 2018. The shorter procedure scheduling freed up additional 40 hours of nursing time in 2020. Also, time in the cath lab was freed up for other procedures (27 hours per year). The complication rate did not change significantly (2,7 % in 2018 and 3,1 % in 2020, P=0,85). The 1-year diagnostic yield for syncope remained high in 2018 and 2020 with no statistically significant difference (26.8 % vs 20.2 % P=0.32). The diagnostic yield for stroke patients implanted in 2020 was 24.6 %. Conclusions Nurse-led care pathways and the use of an external monitoring and triaging service significantly improved the patient pathways for patients indicated for an ICM. This freed up a significant amount of staff time and resources without compromising the quality of the treatment.