Mechanism-based therapy of non-cardiac syncope: a practical guide

The term non-cardiac syncope includes all forms of syncope, in which primary intrinsic cardiac mechanism and non-syncopal transient loss of consciousness can be ruled out. Reflex syncope and orthostatic hypotension are the most frequent aetiologies of non-cardiac syncope. As no specific therapy is effective for all types of non-cardiac syncope, identifying the underlying haemodynamic mechanism is the essential prerequisite for an effective personalized therapy and prevention of syncope recurrences. Indeed, choice of appropriate therapy and its efficacy are largely determined by the syncope mechanism rather than its aetiology and clinical presentation. The two main haemodynamic phenomena leading to non-cardiac syncope include either profound hypotension or extrinsic asystole/pronounced bradycardia, corresponding to two different haemodynamic syncope phenotypes, the hypotensive and bradycardic phenotypes. The choice of therapy-aimed at counteracting hypotension or bradycardia-depends on the given phenotype. Discontinuation of blood pressure-lowering drugs, elastic garments, and blood pressure-elevating agents such as fludrocortisone and midodrine are the most effective therapies in patients with hypotensive phenotype. Cardiac pacing, cardioneuroablation, and drugs preventing bradycardia such as theophylline are the most effective therapies in patients with bradycardic phenotype of extrinsic cause.

Temporal relationship between haemodynamic changes and activation of closed-loop stimulation during a tilt-induced vasovagal syncope

AIMS

A dual-chamber pacemaker with closed-loop stimulation (CLS) mode is effective in reducing syncopal recurrences in patients with asystolic vasovagal syncope (VVS). In this study, we explored the haemodynamic and temporal relationship of CLS during a tilt-induced vasovagal reflex.

METHODS AND RESULTS

Twenty patients underwent a tilt test under video recording 3.9 years after CLS pacemaker implantation. Three patients were excluded from the analysis because of no VVS induced by the tilt test (n = 1) and protocol violation (n = 2). In 14 of the remaining 17 patients, CLS pacing emerged during the pre-syncopal phase of circulatory instability when the mean intrinsic heart rate (HR) was 88 ± 12 b.p.m. and systolic blood pressure (SBP) was 108 ± 19 mmHg. The CLS pacing rate thereafter rapidly increased to 105 ± 14 b.p.m. within a median of 0.1 min [inter-quartile range (IQR), 0.1-0.7 min] when the SBP was 99 ± 21 mmHg. At the time of maximum vasovagal effect (syncope or pre-syncope), SBP was 63 ± 17 mmHg and the CLS rate was 95 ± 13 b.p.m. The onset of CLS pacing was 1.7 min (IQR, 1.5-3.4) before syncope or lowest SBP. The total duration of CLS pacing was 5.0 min (IQR, 3.3-8.3). Closed-loop stimulation pacing was not observed in three patients who had a similar SBP decrease from 142 ± 22 mmHg at baseline to 69 ± 4 mmHg at the time of maximum vasovagal effect, but there was no significant increase in HR (59 ± 1 b.p.m.).

CONCLUSION

The reproducibility of a vasovagal reflex was high. High-rate CLS pacing was observed early during the pre-syncopal phase in most patients and persisted, although attenuated, at the time of maximum vasovagal effect.

REGISTRATION

ClinicalTrials.gov identifier: NCT06038708.

Interventions aimed to increase average 24-h systolic blood pressure reduce blood pressure drops in patients with reflex syncope and orthostatic intolerance

AIMS

Systolic blood pressure (SBP) drops recorded by 24-h ambulatory blood pressure (BP) monitoring (ABPM) identify patients with susceptibility to reflex syncope and orthostatic intolerance. We tested the hypothesis that treatments aimed to increase BP (reassurance, education, and lifestyle measures plus pharmacological strategies) can reduce SBP drops.

METHODS AND RESULTS

This was a multicentre, observational proof-of-concept study performed in patients with reflex syncope and/or orthostatic intolerance and with SBP drops on a screening ABPM. Among 144 eligible patients, 111 underwent a second ABPM on average 2.5 months after start of treatment. Overall, mean 24-h SBP increased from 114.1 ± 12.1 to 121.4 ± 14.5 mmHg (P < 0.0001). The number of SBP drops <90 and <100 mmHg decreased by 61%, 46% during daytime, and by 48% and 37% during 24-h period, respectively (P < 0.0001 for all). The dose-response relationship between difference in 24-h average SBP increase and reduction in number of SBP drops reached a plateau around ∼15 mmHg increase of 24-h SBP. The reduction in SBP drop rate was consistent and significant in patients who underwent deprescription of hypotensive medications (n = 44) and in patients who received BP-rising drugs (n = 67).

CONCLUSION

In patients with reflex syncope and/or orthostatic intolerance, an increase in average 24-h SBP, regardless of the implemented strategy, significantly reduced the number of SBP drops and symptom burden. A 13 mmHg increase in 24-h SBP appears to represent the optimal goal for aborting the maximal number of SBP drops, representing a possible target for future interventions. ClincalTrials.gov identifier: NCT05729724.

Asystole on loop recorder in patients with unexplained syncope and negative tilt testing: age distribution and clinical predictors

BACKGROUND

Approximately 50% of patients with unexplained syncope and negative head-up tilt test (HUTT) who have an electrocardiogram (ECG) documentation of spontaneous syncope during implantable loop recorder (ILR) show an asystolic pause at the time of the event.

OBJECTIVE

The aim of the study was to evaluate the age distribution and clinical predictors of asystolic syncope detected by ILR in patients with unexplained syncope and negative HUTT.

METHODS

This research employed a retrospective, single-center study of consecutive patients. The ILR-documented spontaneous syncope was classified according to the International Study on Syncope of Uncertain Etiology (ISSUE) classification.

RESULTS

Among 113 patients (54.0 ± 19.6 years; 46% male), 49 had an ECG-documented recurrence of syncope during the observation period and 28 of these later (24.8%, corresponding to 57.1% of the patients with a diagnostic event) had a diagnosis of asystolic syncope at ILR: type 1A was present in 24 (85.7%), type 1B in 1 (3.6%), and type 1C in 3 (10.7%) patients. The age distribution of asystolic syncope was bimodal, with a peak at age < 19 years and a second peak at the age of 60-79 years. At Cox multivariable analysis, syncope without prodromes (OR 3.7; p = 0.0008) and use of beta blockers (OR 3.2; p = 0.002) were independently associated to ILR-detected asystole.

CONCLUSIONS

In patients with unexplained syncope and negative HUTT, the age distribution of asystolic syncope detected by ILR is bimodal, suggesting a different mechanism responsible for asystole in both younger and older patients. The absence of prodromes and the use of beta blockers are independent predictors of ILR-detected asystole.

The Rate of Asystolic Reflex Syncope Is Not Influenced by Age

BACKGROUND

The head-up tilt test (HUT) and other evidence suggest that the vagal effect on the heart decreases with age.

OBJECTIVES

The main aim of the study was to assess whether this age effect also affects the rate of asystole in spontaneous reflex syncope (RS).

METHOD

We performed an analysis of pooled individual data from 4 studies that recruited patients ≥40 years of age affected by certain or suspected RS who received an implantable loop recorder (ILR) and reported follow-up data on syncope recurrence. We assessed the presence of asystolic syncope of >3 seconds or nonsyncopal asystole of >6 seconds recorded by ILR and compared the findings to tilt test results on the same patients.

RESULTS

A total of 1,046 patients received ILR because of unexplained syncope. Of these, 201 (19.2%) had a documentation of an asystolic event of 10-second (Q1-Q3: 6- to 15-second) duration. They were subdivided in 3 age tertiles: ≤60 years (n = 64), 61 to 72 years (n = 72), and ≥73 years (n = 65). The rate of asystolic events was similar in the 3 subgroups (50.1%, 50.1%, and 49.2%, respectively; P = 0.99). Conversely, the rate of asystolic syncope induced during HUT (performed in 169 of 201) was greatly age dependent (31.0%, 12.1%, and 11.1% in increasing age tertiles, respectively; P = 0.009).

CONCLUSIONS

The rate of the spontaneous asystolic form of RS documented by ILR is constant at any age >40 years. Conversely, the rate of asystolic syncope induced by HUT is higher in younger patients and decreases with age. The contrasting results between spontaneous and tilt-induced events cast doubt on the concept that asystole in RS is less common in older patients.

Clinical features and response at head-up tilt test of patients with situational syncope

OBJECTIVE

The study compared clinical characteristics and response at head-up tilt test (HUTT) between situational (SS) and vasovagal syncope (VVS).

METHODS

Consecutive patients who underwent nitroglycerin-potentiated HUTT were retrospectively dichotomised into two groups: those with a history of SS and those with a history of VVS. The patients with SS were further subdivided into patients with SS alone and with SS and at least one episode of VVS.

RESULTS

1285 patients were enrolled: 246 (19.1%) had SS (SS alone in 121 and SS+VVS in 125). Patients with SS were older (48.8±20.0 vs 44.4±19.1, p=0.007) and more frequently male (57.3% vs 47.7%, p=0.001). At multivariable analysis, smoking habit (OR 2.28; p<0.0001), history of traumatic syncope (OR 2.29; p=0.0001) and ACE inhibitors/angiotensin II receptor blockers (OR 4.74; p<0.0001) were independently associated with SS. HUTT was positive in 175 (71.1%) patients with SS and in 737 (70.9%) patients with VVS (p=0.9). Patients with SS showed more mixed (42.3% vs 32.0%, p=0.002) and vasodepressor forms (10.6% vs 6.1%, p=0.01) and less cardioinhibitory responses compared with others (18.3% vs 32.8%, p<0.0001).

CONCLUSIONS

Compared with VVS, patients with SS have different clinical characteristics and a higher prevalence of hypotensive drugs leading to hypotensive susceptibility. The positivity rate of HUTT is high and similar to that of VVS, although patients with SS show a higher prevalence of hypotensive responses.

Detection of impending reflex syncope by means of an integrated multisensor patch-type recorder

We assessed the capability of an integrated multisensory patch-type monitor (RootiRx®) in detecting episodes of reflex (pre)syncope induced by tilt table test (TTT). Firstly, we performed an intrapatient comparison of cuffless systolic blood pressure (SBP), R-R interval (RRI) and variability (power spectrum analysis) obtained by means of the RootiRx® with those obtained with conventional methods (CONV) with validated finger pressure devices at baseline in supine position and repeatedly during TTT in 32 patients affected by likely reflex syncope. Secondly, the LF/HF values obtained with RootiRx® during TTT were analyzed in 50 syncope patients. Compared with baseline supine recordings, during TTT a decrement of median SBP was observed with CONV (-53.5 mmHg) but not with RootiRx® ®(-1 mmHg). Conversely, RRI reduction (CONV: 102 ms; RootiRx®: 127 ms) and RRI Low Frequency/High Frequency powers ratio (LF/HF) increase (CONV: 1.6; RootiRx®: 2.5) were similar. The concordance was good for RRI (0.97 [95% CI 0.96-0.98]) and fair for LF/HF ratio (0.69 [95% CI 0.46-0.83]). During the first 5 min of TTT the LF/HF ratio was higher in patients who later developed syncope than in no-syncope patients. This ratio was significantly different among patients with syncope, presyncope or without symptoms at the time of syncope (p value = 0.02). In conclusion, cuffless RootiRx® was unable to detect rapid drops of SBP occurring during impending reflex syncope and thus cannot be used as a diagnostic tool for hypotensive syncope. On the other hand, RRI mean values and LF/HF power ratios obtained with RootiRx® were consistent with those simultaneously obtained using conventional methods.

Twenty-five years of research on syncope

Over the last 25 years, the Europace journal has greatly contributed to dissemination of research and knowledge in the field of syncope. More than 400 manuscripts have been published in the journal. They undoubtedly improved our understanding of syncope. This symptom is now clearly differentiated from other forms of transient loss of consciousness. The critical role of vasodepression and/or cardioinhibition as final mechanisms of reflex syncope is emphasized. Current diagnostic approach sharply separates between cardiac and autonomic pathways. Physiologic insights have been translated, through rigorously designed clinical trials, into non-pharmacological or pharmacological interventions and interventional therapies. The following manuscript is intended to give the reader the current state of the art of knowledge of syncope by highlighting landmark contributions of the Europace journal.

Adenosinergic System and Neuroendocrine Syncope: What Is the Link?

Although very common, the precise mechanisms that explain the symptomatology of neuroendocrine syncope (NES) remain poorly understood. This disease, which can be very incapacitating, manifests itself as a drop in blood pressure secondary to vasodilation and/or extreme slowing of heart rate. As studies continue, the involvement of the adenosinergic system is becoming increasingly evident. Adenosine, which is an ATP derivative, may be involved in a large number of cases. Adenosine acts on G protein-coupled receptors with seven transmembrane domains. A1 and A2A adenosine receptor dysfunction seem to be particularly implicated since the activation leads to severe bradycardia or vasodilation, respectively, two cardinal symptoms of NES. This mini-review aims to shed light on the links between dysfunction of the adenosinergic system and NHS. In particular, signal transduction pathways through the modulation of cAMP production and ion channels in relation to effects on the cardiovascular system are addressed. A better understanding of these mechanisms could guide the pharmacological development of new therapeutic approaches.

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

AIMS

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.

METHODS AND 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.

CONCLUSION

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.

Outcome of the elective or online radiofrequency ablation of typical atrial flutter

BACKGROUND

Radiofrequency ablation of the cavotricuspid isthmus is currently the first-choice treatment of typical atrial flutter and usually it is performed electively. The purpose of this study was to see whether performing on-line ablation has similar clinical results compared to the conventional strategy.

METHODS

Consecutive patients (465) who underwent ablation of the cavotricuspid isthmus for typical atrial flutter (AFL) at our electrophysiology laboratory in the 2008-2017 decade were studied. We evaluated the acute and long-term clinical outcomes of those who were treated electively (337) compared to those who had online ablation (128), that is within 24 hours of presenting to the Department of Cardiology. In patients treated on an emergency basis, a transesophageal echocardiogram was performed to rule atrial thrombi when needed.

RESULTS

No significant intraprocedural difference was observed between the 2 patient groups, with comparable acute electrophysiological success (99% vs. 98%) and serious complications. Even at the subsequent 4-year follow-up, there were no significant differences in the recurrence of typical AFL, onset of atrial fibrillation and other clinical events.

CONCLUSIONS

Online ablation of typical atrial flutter performed at the time of the clinical presentation of the arrhythmia, was shown to be comparable in terms of procedural safety and clinical efficacy in the short and long term compared to an elective ablation strategy.

Short-duration head-up tilt test potentiated with sublingual nitroglycerin in suspected vasovagal syncope: the fast Italian protocol

BACKGROUND

The traditional nitroglycerin (NTG) head-up tilt test (HUTT) is time-consuming and the test duration is a barrier to widespread utilization in clinical practice. It was hypothesized that a short-duration protocol is not inferior to the traditional protocol regarding the positivity rate and has a similar distribution of hemodynamic response.

METHODS AND RESULTS

Patients undergoing HUTT were randomized 1:1 to a 10 min passive phase plus a 10 min 0.3 mg NTG if the passive phase was negative (Fast) or to a 20 min passive phase plus a 15 min 0.3 mg NTG if the passive phase was negative (Traditional). A sample size of 277 patients for each group achieved 80% power to detect an expected difference of 0% with a non-inferiority margin of -10% using a one-sided t-test and assuming a significant level alpha of 0.025. A total of 554 consecutive patients (mean age 46.6 ± 19.3 years, 47.6% males) undergoing HUTT for suspected vasovagal syncope were randomly assigned to the Fast (n = 277) or Traditional (n = 277) protocol. A positive response was defined as the induction of syncope in presence of hypotension/bradycardia, and was observed in 167 (60.3%) patients with Fast and in 162 (58.5%) patients with the Traditional protocol. There was a trend of lesser vasodepressor response (14.8% Fast vs. 20.6% Traditional) which was significant during the passive phase (P = 0.01).

CONCLUSION

The diagnostic value of the Fast HUTT protocol is similar to that of the Traditional protocol and therefore the Fast protocol can be used instead of the Traditional protocol.

Twenty-year experience of atrial fibrillation ablation: a single-centre cohort study

AIMS

While several studies in the literature have reported results of catheter ablation of AF, few is known regarding outcome for more than 10 years.

METHODS AND RESULTS

The complete population of patients who underwent AF ablation in the years 2002-2021 in the department of cardiology of the hospital of Reggio Emilia has been analysed. The last follow-up was made in the second half of 2022. During this period the technique of ablation remained relatively unchanged as well the physicians performing ablation. Primary endpoint was the recurrence of symptomatic AF, defined as AF that caused symptoms that were defined by the patient as able to alter their quality of life. 669 patients underwent catheter ablation and 618 were followed until 2022. Median age of the patients was 58 ± 9 years and 521 (78%) were male. There were 407 (61%) of patients with paroxysmal AF, 167 (25%) with persistent AF and 95 (14%) with long-lasting AF. A total of 838 procedures were performed, with a mean of 1.25 per patient. 163 (26%) patients had 2 procedures and 6 had 3 ablations. Periprocedural complications occurred in 4.8% of procedures. Follow-up data were available for 618 patients (92.4%). The median follow-up duration was 6.6 years (IQR 3.2-10.8). The estimated recurrence rate of symptomatic AF was 26% at 10 years, 54% at 15 years and 82% at 20 years. The recurrence rate was similar in patients who had performed one procedure and in those who had performed 2 or 3 procedures. Progression to permanent AF occurred in 112 patients (18%). The major events that occurred during the follow-up consisted of total mortality in 4.5%, heart failure in 3.1% and TIA/stroke in 2.4%.

CONCLUSION

Symptomatic AF tends to recur during long-term follow-up despite one or more procedures. Catheter ablation seems able to reduce the rate of symptomatic recurrences and to delay the time of their occurrence. These findings are consistent with the knowledge that an age-dependent progressive structural atriomiopathy is the basis for the development of AF.

Twenty-Four-Hour Ambulatory Blood Pressure Profile in Patients With Reflex Syncope and Matched Controls

Background Ambulatory blood pressure (BP) monitoring has long been used to monitor BP in hypertension and lately emerged as a useful tool to detect hypotensive susceptibility in reflex syncope. However, hemodynamic characteristics in reflex syncope have not been sufficiently explored. The present study investigated the differences between ambulatory BP monitoring profiles associated with reflex syncope and normal population. Methods and Results This is an observational study comparing ambulatory BP monitoring data from 50 patients with reflex syncope and 100 controls without syncope, age- and sex-matched 1:2. Mean 24-hour systolic (SBP) and diastolic BP, pulse pressure (24-hour PP), dipping status, and number of daytime SBP drops <90 to 100 mm Hg were analyzed. Variables associated with reflex syncope were investigated using multivariable logistic regression. Patients with reflex syncope displayed significantly lower 24-hour SBP (112.9±12.6 versus 119.3±11.5 mm Hg, P=0.002), higher 24-hour diastolic BP (85.2±9.6 versus 79.1±10.6 mm Hg, P<0.001), and markedly lower 24-hour PP (27.7±7.6 versus 40.3±9.0 mm Hg, P<0.001) compared with controls. Daytime SBP drops <90 mm Hg were more prevalent in patients with syncope (44% versus 17%, P<0.001). Daytime SBP drops <90 mm Hg, 24-hour PP <32 mm Hg, 24-hour SBP ≤110 mm Hg, and 24-hour diastolic BP ≥82 mm Hg were independently associated with reflex syncope, with 24-hour PP <32 mm Hg achieving the highest sensitivity (80%) and specificity (86%). Conclusions Patients with reflex syncope have lower 24-hour SBP but higher 24-hour diastolic BP and more frequent daytime SBP drops <90 mm Hg than individuals without syncope. Our results support the presence of lower SBP and PP in reflex syncope and suggest a role for ambulatory BP monitoring in the diagnostic work-up of this condition.

The clinical presentation of syncope influences the head-up tilt test responses

INTRODUCTION

Little is still known about the positivity rate of nitroglycerin (NTG) potentiated head-up tilt test (HUTT) according to the history-based clinical features of syncope. The study aimed to compare the HUTT positivity rate and type of responses in patients with classical and non-classical vasovagal syncope (VVS).

MATERIALS AND METHODS

We retrospectively evaluated all consecutive patients who underwent NTG-potentiated HUTT for VVS. The study population was dichotomized into classical and non-classical VVS.

RESULTS

A total of 1285 VVS patients (45± 19.1 years; 49.6% male) were enrolled: 627 (48.8%) had a history of classical VVS and 658 (51.2%) of non-classical VVS. HUTT was positive in 866 (67.4%) patients. The positivity rate was significantly higher in patients with classical compared to those with non-classical VVS (81.5% vs 54%; P< 0.0001). Cardioinhibitory response showed similar total positivity rate (27.6% vs 31%; P= 0.17), but higher relative prevalence among positive tests (57.7% vs 33.9%, P< 0.0001) in patients with non-classical VVS. At multivariable analysis, classical reflex syncope, male sex, history of traumatic syncope and use of diuretics were independent predictors of HUTT positivity.

CONCLUSION

The clinical presentation of syncope influences the overall HUTT positivity rate and the type of responses. Cardioinhibitory response and traumatic syncope are more likely in patients with non-classical VVS.

Prevalence of asystole during tilt test-induced vasovagal syncope may depend on test methodology

This review addresses tilt-testing methodology by searching the literature which reports timing of asystole and loss of consciousness (LOC). Despite the Italian protocol being the most widely adopted, its stipulations are not always followed to the letter of the European Society of Cardiology guidelines. The discrepancies permit reassessment of the incidence of asystole when tilt-down is early, impending syncope, compared with late, established LOC. Asystole is uncommon with early tilt down and diminishes with increasing age. However, if LOC is established as test-end, asystole is more common, and it is age-independent. Thus, the implications are that asystole is commonly under-diagnosed by early tilt-down. The prevalence of asystolic responses observed using the Italian protocol with a rigorous tilt down time is numerically close to that observed during spontaneous attacks by electrocardiogram loop recorder. Recently, tilt-testing has been questioned as to its validity but, in selection of pacemaker therapy in older highly symptomatic vasovagal syncope patients, the occurrence of asystole has been shown to be an effective guide for treatment. The use of head-up tilt test as an indication for cardiac pacing therapy requires pursuing the test until complete LOC. This review offers explanations for the findings and their applicability to practice. A novel interpretation is offered to explain why pacing induced earlier may combat vasodepression by raising the heart rate when sufficient blood remains in the heart.

Tests for the identification of reflex syncope mechanism

INTRODUCTION

Treatment efficacy of reflex syncope is mainly related to the mechanism underlying syncope rather than its etiology or clinical presentation. The predominant mechanism underlying reflex syncope can be assigned to hypotensive or to bradycardic phenotypes.

AREAS COVERED

Methodology and diagnostic criteria of the most useful tests for the identification of hypotensive and bradycardic phenotypes are discussed. Diagnostic tests for the hypotensive phenotype include office blood pressure measurement with active standing test, home, and wearable blood pressure monitoring, 24-h ambulatory blood pressure monitoring and tilt table test. Diagnostic tests for the bradycardic phenotype include carotid sinus massage, tilt table test and prolonged ECG monitoring.

EXPERT OPINION

In reflex syncope, the documentation of bradycardia/asystole during a syncopal episode does not rule out the possibility that a preceding or parallel hypotensive reflex plays an important role. Similarly, even when a hypotensive mechanism is established, the possibility of an associated cardioinhibitory reflex should be investigated. Investigating the mechanism of reflex syncope is mandatory in patients with severe recurrent episodes, with the final aim to develop a personalized treatment strategy. Recent trials have demonstrated the benefits of personalized mechanism-based therapy, thus highlighting the importance of a comprehensive assessment of the mechanisms underlying syncope.

Low incidence of arrhythmic syncope and pacemaker implantation in older patients with bifascicular block and implantable cardiac monitor

BACKGROUND

In patients with unexplained syncope, bifascicular block (BFB) is considered associated with syncope due to either heart block or sinus arrest. Immediate or delayed pacemaker (PM) implantation after ECG documentation of syncopal recurrence by means of implantable cardiac monitors (ICM) is still debated. We aimed to assess the incidence of recurrent syncope and guideline-based PM implantation in patients with syncope and BFB implanted with ICM.

METHODS

Consecutive patients with syncope and BFB followed at two tertiary care syncope units and implanted with ICM from 2012 to 2020 were retrospectively reviewed. Only patients with ≥2 clinical visits and ≥ 18 years of age were included. Incidence of a Class I indication for PM implantation was the primary outcome.

RESULTS

Of 635 syncope patients implanted with an ICM, 55 (8.7%) had a BFB and were included. Median age at implantation was 75 [interquartile range, IQR:64-81] years, and 28(49.1%) were women. At 26 [IQR:12-41] months follow-up, 20 (36.3%,16.3%/year) patients experienced syncope: in 6(10.9%) patients syncope was classified 'arrhythmic' with a higher prevalence in older individuals (p = 0.048). PM implantation (N = 14,25.5%) was more frequent in patients ≥75 years (p = 0.024). At survival analysis, patients ≥75 years were at highest risk of arrhythmic syncope and guideline directed PM implantation (Hazard Ratio: 4.5, 95% Confidence Intervals 1.5-13.3).

CONCLUSIONS

Most older patients with syncope who received an ICM did not have events during follow-up. One-in-three experienced syncope, and an even smaller number had an arrhythmic syncope with indication for PM implantation. Older age was strongly associated with PM implantation.

Syncope in hypertrophic cardiomyopathy (part II): An expert consensus statement on the diagnosis and management

Syncopal events in patients with hypertrophic cardiomyopathy (HCM) are of concern as they are a vital consideration in algorithms for risk stratification for sudden cardiac death (SCD) and ICD implantation. However, the cause of syncope is often under-investigated and/or unexplained. Current syncope guidelines do not provide a detailed definition of unexplained syncope. To address this important gap, an international panel of experts in the field of both syncope and HCM wrote a consensus document with the aim of providing practical guidance for the diagnosis and management of syncope in patients with HCM.

946 TAKOTSUBO SYNDROME TRIGGERED BY REFLEX SYNCOPE: A POTENTIALLY FATAL COMPLICATION OF A BENIGN CONDITION

Introduction

Vasovagal syncope is traditionally considered a benign condition due to parasympathetic nervous system activation. Here is a case of reflex syncopal episodes that triggered recurrent Takotsubo Syndrome (TS) with life–threatening presentation.

Report of a Case

A 71-year-old female presented to the Emergency Department (ED) complaining with dyspnoea and chest pain developed half an hour after a vasovagal syncope. Her past medical history was consistent with arterial hypertension, dyslipidaemia, and well-tolerated reflex syncopal episodes since she was a child. At hospital admission, a 12-leads ECG showed T-wave inversion in anterior leads while transthoracic echocardiogram (TTE) showed hypokinesia of the mid-apical segments, reduced left ventricular ejection fraction (LVEF) [40%], and severe mitral regurgitation (MR). Blood tests revealed increased hs-troponin I values [peak value: 1500 ng/L]. A coronary angiography (CA) was thus performed in the suspect of NSTEMI, showing non obstructive coronary disease. A diagnosis of TS was eventually made with ECG normalisation and resolution of echocardiographic abnormalities at 6 month follow-up. Five years later, the patients presented to the ED because of a new syncopal episode followed by severe pulmonary oedema. Since the presence of electrocardiographic T-wave inversion, apical segments akinesia and elevated hs-troponin I were consistent with NSTEMI, a CA was performed revealing (again!) normal coronary vessels. A suspect of TS relapse was thus made. Three months after discharge, ECG and echocardiogram were normal and a syncope diagnostic work–up was suggested. A 24/h ambulatory blood pressure monitoring demonstrated normal pressure values and a tilt test confirmed the well-established history of reflex syncope showing a remarkable cardioinhibitory response. A pacemaker implant was thus indicated.

Discussion

TS is a heart syndrome characterized by transient contractile dysfunction historically related to catecholamine activation of alpha and beta receptors. While sympathetic system involvement in the development of TS is clearly established, new evidence is emerging about the vagal role in the etiopathogenesis of the disease. Although syncopal episodes could be related to TS, because of LVOT obstruction or major arrhythmias, according to our experience, TS may be triggered by vagal hypertonus [i.e., after vasovagal syncopal episodes]. In similar situation, the implantation of a pace-maker could be considered to prevent future dangerous complications related to recurrent reflex syncope even if well tolerated by the patients.

Conclusion

In our experience, recurrent episodes of TS appeared triggered by reflex syncope. A condition traditionally considered benign may instead have life-threatening consequences. Moreover, the role of parasympathetic and vagal tone in the development of TS needs further investigation that may lead to the design of new strategies of clinical diagnosis and management.

595 LOW INCIDENCE OF ARRHYTHMIC SYNCOPE AND PACEMAKER IMPLANTATION IN OLDER PATIENTS WITH BIFASCICULAR BLOCK AND IMPLANTABLE CARDIAC MONITOR

Background

In patients with unexplained syncope, bifascicular block (BFB) is considered associated with syncope due to either heart block or sinus arrest. Immediate or delayed pacemaker (PM) implantation after ECG documentation of syncopal recurrence by means of implantable cardiac monitors (ICM) is still debated. We aimed to assess the incidence of recurrent syncope and guideline-based PM implantation in patients with syncope and BFB implanted with ICM.

Methods

Consecutive patients with syncope and BFB followed at two tertiary care syncope units and implanted with ICM from 2012 to 2020 were retrospectively reviewed. Only patients with &gt;2 clinical visits and &gt;18 years of age were included. Incidence of a Class I indication for PM implantation was the primary outcome.

Results

Of 635 syncope patients implanted with an ICM, 55 (8.7%) had a BFB and were included. Median age at implantation was 75 [interquartile range, IQR:64-81] years, and 28(49.1%) were women. At 26 [IQR:12-41] months follow-up, 20 (36.3%,16.3%/year) patients experienced syncope: in 6(10.9%) patients syncope was classified ‘arrhythmic’ with a higher prevalence in older individuals (p=0.048). PM implantation (N=14,25.5%) was more frequent in patients &gt;75 years (p=0.024). At survival analysis, patients &gt;75 years were at highest risk of arrhythmic syncope and guideline directed PM implantation (Hazard Ratio: 4.5, 95% Confidence Intervals 1.5-13.3).

Conclusions

Most older patients with syncope who received an ICM didn't have events during follow-up. Only one-in-three experienced syncope, and an even smaller number had an arrhythmic syncope with indication for PM implantation. Older age was strongly associated with PM implantation.

313 BRUGADA SYNDROME MIMICRY: THE IMPORTANCE OF AN EXTENDED FOLLOW-UP

Introduction

Brugada Syndrome (BrS) is a genetically inherited condition associated with the risk of fatal arrhythmias and sudden cardiac death (SCD) occurring in a structurally normal heart. This disorder was historically related to mutations in the SCN5A gene, but recent observations suggest a more complex genetic inter-play, highlighting the possible overlap with structural cardiomyopathies, including hypertrophic cardiomyopathy (HCM).

Case Presentation

In May 2005, an asymptomatic 56-year-old man with a family history of unexplained SCD was referred to our outpatient clinic. A 12-lead ECG showed a type 2 Brugada pattern whilst transthoracic echocardiogram (TTE) was normal. Ventricular fibrillation (VF) was induced during an elective electrophysiological study and a transvenous implantable cardioverter-defibrillator (ICD) was implanted for primary prevention. More than 10 years later, in March 2022, our patient was admitted to the hospital because of palpitations. The ECG revealed a typical atrial flutter with a high ventricular rate, successfully treated with catheter ablation. Post-procedural ECG showed the persistence of type 2 Brugada pattern in association with new-onset T wave inversion in inferolateral leads and signs of ventricular hypertrophy. TTE revealed asymmetric left ventricular hypertrophy, with left ventricular outflow tract (LVOT) obstruction determined by mitral systolic anterior motion and preserved LV systolic function. The patient was treated with optimal medical therapy with symptom improvement and reduction of LVOT obstruction at a 3-month follow-up TTE.

Discussion

The distinction between Brugada phenocopy and BrS electrocardiogram patterns is not obvious, and according to our experience a Brugada type 2 pattern could be an early ECG marker of a concealed HCM which became manifest over an extended follow-up. Brugada ECG phenocopies are clinical entities characterized by type 1 or type 2 Brugada patterns elicited by an underlying condition, the disappearance of the pattern with the resolution of the condition and the absence of classical symptoms. Several pathogenic variants involving other and different genes have been recently reported suggesting a possible overlap with structural cardiomyopathies. Recently, two other cases of incidental findings of a Brugada ECG pattern in the context of HCM were described. Both patients had a common pathogenetic splicing mutation in the MYBPC3 sarcomeric gene (encoding for the cardiac myosin-binding protein C) responsible for HCM with no genetic mutations associated with Brugada syndrome. This fact suggests that patients are not simultaneously affected by BrS and HCM but a clinically manifest HCM with a specific genetic background can lead to an early BrS electrical manifestation.

Conclusion

Our experience confirms that a Brugada type 2 ECG pattern could be a very early sign of a concealed HCM manifested over 10 years later. The importance of proper risk stratification and regular follow-up has thus crucial implications in patient clinical management. However, whether Brugada pattern associated with structural heart disease is linked to an increased risk of sudden cardiac death is still unknown and needs further investigations.

A novel and practical method to add video monitoring to tilt table testing

AIMS

We describe a novel, practical, and inexpensive method to add video recording during tilt table testing (TTT): Open-Access-Video-TTT.

METHODS AND RESULTS

The Open-Access-Video-TTT set-up uses a personal computer (PC) to capture screen video data from a non-invasive-beat-to-beat (NIBTB) haemodynamic blood pressure (BP) device, combined with video recording of a patient, using Open Broadcaster Software (OBS®). The new Open-Access-Video-TTT set up was tested with both the Finometer (model Finapres Nova®, Medical Systems, the Netherlands) and the Task Force® Touch Cardio monitor (CNSystems, Austria). For this, the Finapres Nova® was enabled in 'remote' mode and Real Video Network Computing (RealVNC®) was installed on the PC/laptop. The Task Force® has a DisplayPort (DP) port, for which a DP/ high-definition multimedia interface (HDMI) cable and a video capture card is used to merge the signals to the PC/laptop. With this method the combined images are stored as a new video signal. TTT can be performed with any routine protocol.

CONCLUSIONS

Open Access-Video-TTT worked well for both the Finapres NOVA® and the Task Force Monitor ®. This novel method can be used easily by all physicians who wish to add video recording during TTT who do not have access to an electroencephalogram machine.

New definition of hypotension in patients with reflex syncope using 24-hour ambulatory blood pressure monitoring (SynABPM Study)

Background

Diagnostic criteria for ambulatory blood pressure monitoring (ABPM) in patients with suspected reflex syncope are lacking.

Purpose

We hypothesized that patients with reflex syncope have a higher prevalence of systolic blood pressure (SBP) drops on ABPM than control subjects and we aimed to define the SBP cut-off values that allow identification of patients with hypotensive susceptibility.

Methods

We compared ABPM data from reflex syncope patients and controls, matched by average 24-hour SBP, age, sex and hypertension. Patients with constitutional hypotension, orthostatic hypotension, predominant cardioinhibition or competing causes of syncope were excluded. Daytime and night-time SBP drops (&lt;110, 100, 90, 80 mmHg) were assessed. Findings were validated in an independent sample.

Results

In the Derivation cohort, daytime SBP drops were significantly more common in 158 syncope patients than 329 controls. One or more daytime drop &lt;90 mmHg provided the best diagnostic yield (91% specificity, 32% sensitivity, Odds Ratio [OR]=4.6, p=0.001). Two or more-daytime drops &lt;100 mmHg achieved 84% specificity and 40% sensitivity (OR=3.5, p=0.001). Results were confirmed in the Validation cohort: one or more daytime SBP drop &lt;90 mmHg provided 94% specificity and 29% sensitivity (OR=6.2, p&lt;0.001), while two or more daytime SBP drops &lt;100 mmHg achieved 83% specificity and 35% sensitivity (OR=2.6, p&lt;0.001) (Figure 1).

Conclusion

SBP drops during ABPM are more common in reflex syncope patients than in controls. Cut-off values that may be applied in clinical practice are defined. This study expands the current indications for ABPM to patients with reflex syncope.

Funding Acknowledgement

Type of funding sources: None.

Feasibility of Blood Pressure Measurement With a Wearable (Watch-Type) Monitor During Impending Syncopal Episodes

Background

We assessed the reliability and feasibility of blood pressure (BP) measurements by means of a new wearable watch‐type BP monitor (HeartGuide) in detecting episodes of hypotensive (pre)syncope induced by tilt table test.

Methods and Results

An intrapatient comparison between systolic BP (SBP) measured by means of the HeartGuide device and noninvasive finger beat‐to‐beat BP monitoring was undertaken both at baseline in supine position and repeatedly during tilt table test in patients evaluated for reflex syncope. Intrapatient fall of systolic BP from baseline was measured. Eighty‐one patients (mean age, 61±19 years; 46 women) were included. Overall, HeartGuide was able to yield BP values at the time of BP nadir in 58 (72%) patients (average HeartGuide SBP 102±18 mm Hg, versus finger SBP 101±19 mm Hg). Compared with baseline, the maximum SBP decrease was on average −28.5±27.8 and −30.3±33.9 mm Hg respectively (Lin's concordance correlation coefficient=0.78, r=0.79, P=0.001). In the subgroup of 38 patients with tilt table test induced (pre)syncope, the average HeartGuide SBP during symptoms was 97±16 mm Hg, and the finger SBP was 94±18 mm Hg. Compared with baseline, the maximum SBP decrease was on average −35.2±29.3 and −43.3±31.8 mm Hg, respectively (Lin's concordance correlation coefficient=0.83, r=0.87, P=0.001).

Conclusions

Our data indicate that the HeartGuide BP monitor can detect low BP during presyncope and that its measure of SBP change is consistent with that simultaneously obtained through continuous BP monitoring, despite some intrapatient variability. Thus, this device might be useful in determining the hypotensive nature of spontaneous (pre)syncopal symptoms, a possibility that should be verified by field studies.

Adenosine Concentration in Patients With Neurally Mediated Syncope

Background

Either high or low values of adenosine blood level (ABL) can differentiate some forms of neurally mediated syncope (NMS). A rapid method of measurement has recently been developed. The aim of the present study was: (1) to compare ABLs in an unselected population of consecutive patients referred for evaluation of suspected NMS syncope and in healthy controls; and (2) to assess the relative prevalence of low and high adenosine forms among an unselected syncope population.

Method

Whole blood was collected after finger puncture, blood being deposit on a blot paper and adenosine concentration was measured by liquid chromatography/mass spectrometry (LC-MS/MS).

Results

Among 89 control subjects, the median ABL value was 0.54 μM (IQR, 0.46–0.65). The lowest 5% and the upper 95% percentile were 0.40 and 0.80 μM, respectively. Compared with healthy subjects, the 146 patients with syncope showed, on average, a higher median ABL value [0.63 (IQR 0.45–0.73, p = 0.04)] and a larger distribution of values. Low ABL values below the 5th percentile were observed in 28 (19%) patients, and, in five controls, p = 0.003 and high ABL values were observed in 26 (18%) patients and five controls, p = 0.009.

Conclusions

ABL is different in patients with suspected NMS than in healthy subjects. Patients with low and high adenosine values account for 19% and 18% of the general population. Thus, low and high ABL limits, as defined in this study, may help to define the purinergic profile of unselected subjects with a clinical diagnosis of suspected NMS.

Association between hypotension during 24 h ambulatory blood pressure monitoring and reflex syncope: the SynABPM 1 study

AIMS

Diagnostic criteria for ambulatory blood pressure monitoring (ABPM) in patients with suspected reflex syncope are lacking. The study hypothesis was that patients with reflex syncope have a higher prevalence of systolic blood pressure (SBP) drops on ABPM.

METHODS AND RESULTS

ABPM data from reflex syncope patients and controls, matched by average 24 h SBP, age, sex, and hypertension were compared. Patients with constitutional hypotension, orthostatic hypotension, and predominant cardioinhibition during carotid sinus massage or prolonged electrocardiogram monitoring or competing causes of syncope were excluded. Daytime and nighttime SBP drops (<110, 100, 90, 80 mmHg) were assessed. Findings were validated in an independent sample. In the derivation sample, daytime SBP drops were significantly more common in 158 syncope patients than 329 controls. One or more daytime drops <90 mmHg achieved 91% specificity and 32% sensitivity [odds ratio (OR) 4.6, P < 0.001]. Two or more daytime drops <100 mmHg achieved 84% specificity and 40% sensitivity (OR 3.5, P = 0.001). Results were confirmed in the validation sample of 164 syncope patients and 164 controls: one or more daytime SBP drops <90 mmHg achieved 94% specificity and 29% sensitivity (OR 6.2, P < 0.001), while two or more daytime SBP drops <100 mmHg achieved 83% specificity and 35% sensitivity (OR 2.6, P < 0.001).

CONCLUSION

SBP drops during ABPM are more common in reflex syncope patients than in controls. Cut-off values that may be applied in clinical practice are defined. This study expands the current indications for ABPM to patients with reflex syncope.

Safety, Pharmacokinetic, and Pharmacodynamic Study of a Sublingual Formula for the Treatment of Vasovagal Syncope

Background

Vasovagal syncope is a common cause of syncope which, if recurrent, can have multiple negative consequences such as injury and occupational disability. Various medications can be used to decrease the recurrence of vasovagal syncope but there are no drugs that can be used by patients to interrupt a perceived vasovagal episode.

Methods

A phase I study was performed to evaluate the tolerability and safety of a gel formulation containing capsaicin (1 mg), phenylephrine HCL (PE) and caffeine citrate (200 mg) (CPC) in normal adult volunteers. Secondary objectives were to characterize the pharmacokinetics (PK) of the CPC formulation and the highest dose of PE needed to achieve a target increase in systolic BP of at least 40 mmHg. After receiving the first dose, a second dose of the CPC mixture was administered at 2 h. Suboptimal changes in systolic blood pressure (SBP) were noted at PE doses of 0.6, 1.2, and 1.8 mg, therefore a second cohort was studied at PE doses of 10, 20, and 30 mg. Blood samples were collected in rapid sequence and were assayed for all three drugs.

Results

A total of 17 subjects received the drug with no serious adverse effects reported. All doses were well tolerated, although the capsaicin content usually caused expected temporary oral and gastric discomfort. One subject did not complete the study because of a vasovagal reaction that was associated with the frequent blood sampling. There was a 5–25 min lag in the appearance of measurable blood concentrations of capsaicin and phenylephrine. Most subjects had baseline caffeine concentrations from dietary use, with a gradual increase noted after 15 min consistent with GI absorption. Although the intended criterion of a 40 mmHg increase in SBP was not reached, a clinically significant increase in BP for at least 15 min was noted in the six subjects who received the highest dose of PE (30 mg), with a gradual decline over the next 2 h.

Conclusion

The ternary mixture of capsaicin, phenylephrine, and caffeine was well tolerated when administered as two sublingual/oral doses over a 2-h period.

Randomized Pragmatic Trial of Pacemaker Versus Implantable Cardiac Monitor in Syncope and Bifascicular Block

OBJECTIVES

In this study, the authors tested whether a strategy of empiric permanent pacing reduces major composite events more effectively than acting on the results of an implantable cardiac monitor (ICM).

BACKGROUND

Syncope may be caused by intermittent complete heart block in patients with bifascicular heart block, but competing diagnoses coexist. Whether empiric permanent pacing or acting on investigative results provides best care is unknown.

METHODS

This was a multinational, randomized, pragmatic clinical trial of patients ≥50 years of age with bifascicular block, preserved left ventricular function, and ≥1 syncope in the preceding year. The primary composite outcome measure comprised cardiovascular death, syncope, bradycardia resulting in pacemaker insertion, and device complications.

RESULTS

There were 57 and 58 subjects randomized to receive a pacemaker or ICM. A total of 41 patients had left bundle branch block and 74 had right bundle branch block and a left fascicular block. Patients were followed for a median 33 months. There were fewer composite primary outcomes in patients randomized to pacemaker compared with ICM, respectively (20 [35%] vs 44 [76%]; chi square P < 0.0001), with lower actuarial probabilities of a primary outcome (0.45 and 1.00; P < 0.001). Syncope was as likely in the groups randomized to receive a pacemaker or ICM (29% vs 26%, chi-square P = 0.95).

CONCLUSIONS

Empiric permanent pacing compared with ICM reduced major adverse events but not syncope in older patients with bifascicular block and recent syncope. There remains a substantial likelihood of syncope recurrence in patients who receive a permanent pacemaker likely caused by vasodepressor syncope. (Syncope: Pacing or Recording in the Later Years [SPRITELY]; NCT01423994).

OUP accepted manuscript

Aims

Methods and results

Conclusion

Cardiac Pacing in Cardioinhibitory Reflex Syncope: Clinical Use of Closed-loop Stimulation

Cardiac pacing has been studied extensively in patients with reflex syncope over the past two decades. The heterogeneity of the forms and clinical manifestations of reflex syncope explain the controversial results of older randomised clinical trials. New evidence from recent trials has changed medical practice, now leading to clear indications for pacing in patients with asystolic syncope documented during carotid sinus massage, implantable cardiac monitoring or tilt testing. Given that recent trials in reflex syncope have been performed using the closed-loop stimulation algorithm, the authors will briefly discuss this pacing mode, review hypotheses about the mechanisms underlying its activation during syncope and provide practical instructions for programming and troubleshooting.

Theophylline in patients with syncope without prodrome, normal heart, and normal electrocardiogram: a propensity-score matched study verified by implantable cardiac monitor

AIMS

Syncope without prodromes in subjects with normal heart and normal electrocardiogram (ECG) is classified as non-classical neurally mediated syncope and is characterized by low adenosine plasma levels (APLs) and frequent asystolic syncope. We assessed the efficacy of theophylline, a non-selective adenosine receptor antagonist, in preventing syncopal events.

METHODS AND RESULTS

Participants received an implantable cardiac monitor, underwent APL measurement, and received oral theophylline at maximum tolerated dose (starting dose 300 mg b.i.d.). They were compared with a historical cohort of untreated patients with implantable cardiac monitor who had the same inclusion criteria and were balanced with the propensity score (PS) method as regard age, sex, lifetime syncopal episodes, APL, and antihypertensive drugs. Primary endpoint was time to first syncopal recurrence at 24 months. There were 76 patients in the theophylline group and 58 in the control group. Syncope recurred in 25 (33%) patients in the theophylline group and in 27 (47%) patients in the control group, with an estimated 2-year recurrence rate of 33% and 60%, respectively, and a hazard ratio of 0.53 [95% confidence interval (CI), 0.30-0.95; P = 0.034]. Most of the benefit of theophylline is derived from reduction of syncope due to asystolic atrioventricular (AV) block (hazard ratio of 0.13; 95% CI, 0.03-0.58; P = 0.008). Thirty (39%) patients discontinued theophylline after a median of 6.4 (interquartile range 1.7-13.8) months due to side effects.

CONCLUSION

Theophylline was effective in preventing recurrences in patients with syncope without prodromes, normal heart, and normal ECG. The benefit was greater in patients with syncope due to asystolic AV block.

CLINICALTRIALS.GOV IDENTIFIER

NCT03803215.

Syncope: new solutions for an old problem

Syncope is a frequent event in the general population. Approximately 1%-2% of all emergency department admissions are due to syncope and at least one-third of all people experience fainting in their life. Although consequences of cardiac syncope are generally feared, non-cardiac syncope is much more common and may be associated with severe injuries and quality-of-life impairment, particularly in older adults. Various diagnostic and therapeutic strategies have been created and implemented over decades, leading to significant improvements in diagnostic accuracy and treatment effectiveness. In recent years, diagnosis and treatment have further evolved according to an innovative approach focused on the hemodynamic mechanism underlying syncope, based upon the assumption that knowledge of the syncope mechanism is a prerequisite for effective syncope prevention and treatment. Therefore, a new classification of syncope has been proposed, which defines two main syncope phenotypes with different predominant mechanisms: the hypotensive phenotype, where hypotension or vasodepression prevails, and the bradycardic phenotype, where cardioinhibition prevails. Identification of syncope phenotype - bradycardic or hypotensive/vasodepressive - represents the first step towards personalized management of syncope, characterized by customized interventions for prevention. The present review aims to illustrate these new developments in the diagnosis and therapy of non-cardiac syncope within a mechanism-based perspective. Diagnosis and therapy of bradycardic and hypotensive phenotypes are discussed, with a focus on recent evidence.

Lifelong and mature-onset syncope in older adults may have different mechanisms

Background

Syncope is a common clinical problem with a sharp rise in the incidence after 70 years. In older patients, syncope is often a diagnostic challenge. It is unclear whether the age at which patients experience syncope for the first time impacts the results of syncope investigation.

Purpose

To study the influence of early-onset vs. mature-onset syncope on clinical characteristics and final head-up tilt (HUT) diagnosis in a large sample of unexplained syncope patients.

Methods

Consecutive patients (n=1928) with unexplained syncope after initial evaluation examined with a standard HUT protocol in a syncope unit were stratified into age groups below and above 60 years. Clinical characteristics and the final HUT diagnosis were analysed in relation to self-reported age at first syncope and age at investigation. The distribution of age at first syncope was bimodal with peaks at 15 and 70 years (Figure 1). In the present analysis, patients aged &gt;60 years (n=836) with early-onset (&lt;30 years) and mature-onset (&gt;60 years) syncope were compared.

Results

Vasovagal syncope (VVS) was more common in early-onset syncope, 39% vs 19% (p&lt;0.001), (Figure 2). Orthostatic hypotension (OH) was more common in mature-onset syncope, 23% vs 7% (p&lt;0.001), as was hypertension, 59% vs 40% (p=0.001). The frequency of carotid sinus syndrome (CSS) was not affected by age at first syncope in patients aged &gt;60 years.Complex syncope etiology (findings suggesting overlap between VVS, OH and/or CSS) was more common among patients with early-onset syncope, 37% vs 26% (p=0.023). No definite HUT-derived diagnosis was more common in mature-onset syncope, 23% vs 13% (p=0.023). Heart failure, 9% vs 2% (p=0.024) and atrial fibrillation, 20% vs 9% (p=0.013) were more common in mature-onset syncope. Prodromes were less common in mature-onset syncope, 26% vs 52% (p&lt;0.001), however there was no significant difference in reported palpitations preceding syncope and dizziness on standing.

Conclusions

Mature-onset syncope was more often associated with absence of prodromes, orthostatic hypotension, inconclusive HUT findings and presence of heart failure and atrial fibrillation suggesting cardiac syncope to be the likely cause. Early-onset syncope was associated with presence of prodromes, vasovagal reflex mechanism and complex syncope diagnosis. Lifelong and mature-onset unexplained syncope may have different pathophysiological mechanisms in older patients and aetiologies other than vasovagal syncope should be carefully considered in patients with first-ever syncope in later life.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swedish heart and lung foundationCrafoord foundation

The relationship between anatomy and electrical parameters in His bundle pacing

Background

The relationship between anatomy and electrical parameters of His bundle (HB) pacing has not been extensively studied.

Purpose

To characterize the anatomical location of the HB lead tip and its relationship with acute electrical parameters.

Methods

Consecutive patients who underwent HB lead implantation, guided by standard fluoroscopy and electrophysiology, were prospectively enrolled. The relationship between HB lead tip and tricuspid valve plane (TVP) was assessed with post-procedure transthoracic echocardiography.

Results

Twenty-five patients were studied. In 11 patients (44%), the HB lead tip did not cross the TVP (A group): in 7 cases it was screwed in the right atrium at a mean distance of −6.1 mm from the TVP and, in 4 cases, at the level of the tricuspid annulus. In the remaining 14 patients (56%), the lead tip crossed the TVP (V group): it was screwed in the right ventricle at a mean distance of 9.3 mm from the TVP. A and V groups had comparable HB capture thresholds (1.6±1 V vs 1.7±0.7 V, 1 ms pulse-width; p=0.66); selective HB capture was significantly more represented in the A group (91% vs 21%; p=0.001). Significantly higher R-wave amplitudes were seen in the V group (6.7±3 vs 2.5±1.7 mV; p=0.0004), and they positively correlated with the distance from the TVP (p=0.0038). Atrial oversensing was never observed.

Conclusion

In a consecutive cohort of HBP recipients, the rate of patients who had an effective HB capture in the atrium was substantial and was characterized by different electrophysiological properties than in the ventricle.

Funding Acknowledgement

Type of funding sources: None.