Five waves of COVID-19 pandemic in Italy: results of a national survey evaluating the impact on activities related to arrhythmias, pacing, and electrophysiology promoted by AIAC (Italian Association of Arrhythmology and Cardiac Pacing)

BACKGROUND

The subsequent waves of the COVID-19 pandemic in Italy had a major impact on cardiac care.

METHODS

A survey to evaluate the dynamic changes in arrhythmia care during the first five waves of COVID-19 in Italy (first: March-May 2020; second: October 2020-January 2021; third: February-May 2021; fourth: June-October 2021; fifth: November 2021-February 2022) was launched.

RESULTS

A total of 127 physicians from arrhythmia centers (34% of Italian centers) took part in the survey. As compared to 2019, a reduction in 40% of elective pacemaker (PM), defibrillators (ICD), and cardiac resynchronization devices (CRT) implantations, with a 70% reduction for ablations, was reported during the first wave, with a progressive and gradual return to pre-pandemic volumes, generally during the third-fourth waves, slower for ablations. For emergency procedures (PM, ICD, CRT, and ablations), recovery from the initial 10% decline occurred in most cases during the second wave, with some variability. However, acute care for atrial fibrillation, electrical cardioversions, and evaluations for syncope showed a prolonged reduction of activity. The number of patients with devices which started remote monitoring increased by 40% during the first wave, but then the adoption of remote monitoring declined.

CONCLUSIONS

The dramatic and profound derangement in arrhythmia management that characterized the first wave of the COVID-19 pandemic was followed by a progressive return to the volume of activities of the pre-pandemic periods, even if with different temporal dynamics and some heterogeneity. Remote monitoring was largely implemented during the first wave, but full implementation is needed.

Performance of a multisensor implantable defibrillator algorithm for HF monitoring in presence of comorbidities

Background

Cardiovascular and non-cardiovascular comorbidities are common in heart failure (HF) patients and impact disease severity and prognosis. Select modern implantable defibrillators (ICDs) are equipped with multisensor algorithms for HF monitoring. The HeartLogic index combines multiple ICD-based sensor data (heart rate, heart sounds, thoracic impedance, respiration, activity), and the associated alert has proved to be a sensitive and timely predictor of impending HF decompensation in cardiac resynchronization therapy (CRT-D) patients The algorithm was developed using data from CRT-D patients; the performance in non-CRT ICD patients and the impact of selected comorbidities on performance requires further study.

Methods

The HeartLogic feature was activated in 568 ICD patients (410 with CRT) from 26 centers. The median follow-up was 25 months [25th–75th percentile: 15–35].

Results

During follow-up, 97 hospitalizations were reported (53 cardiovascular) and 55 patients died. We recorded 1200 HeartLogic alerts (0.71 alerts/patient-year) in 370 patients. Overall, the time IN the alert state was 13% of the total observation period. The rate of cardiovascular hospitalizations or death was 0.48/patient-year (95% CI: 0.37–0.60) with the HeartLogic IN alert state and 0.04/patient-year (95% CI: 0.03–0.05) OUT of alert state, with an incidence rate ratio of 13.35 (95% CI: 8.83–20.51, p<0.001). Among patient characteristics, atrial fibrillation (AF) at implantation (HR: 1.62, 95% CI: 1.27–2.07, p<0.001) and chronic kidney disease (CKD) (HR: 1.53, 95% CI: 1.21–1.93, p<0.001) independently predicted alerts. HeartLogic alerts were not associated with CRT vs. non-CRT device implantation (HR: 1.03, 95% CI: 0.82–1.30, p=0.775). The comparisons of the clinical event rates in the IN alert state with those in the OUT of alert state yielded incidence rate ratios ranging from 9.72 to 14.54 (all p<0.001) in all groups of patients stratified by: CRT/non-CRT, AF/non-AF, CKD/non-CKD. Indeed, after multivariate correction for CKD and AF at implantation, the time IN the HeartLogic alert state >13% was associated with the occurrence of the combined endpoint of cardiovascular hospitalization or death (HR: 2.54, 95% CI: 1.61–4.01, p<0.001).

Conclusions

The burden of HeartLogic alerts appears similar between CRT and non-CRT patients, while patients with AF and CKD seem more exposed to alerts. Nonetheless, the ability of the HeartLogic algorithm to identify patients during periods of significantly increased risk of clinical events is confirmed regardless of the type of device, the presence of AF, or CKD.

Funding Acknowledgement

Type of funding sources: None.

Biosensors in cardiology. T-CARE project: a preliminary study on an innovative wearable telemonitoring system

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): REGIONE PUGLIA

Introduction

The demographic trend evolution and the modification of health needs highlight the requirement for a novel organization of the healthcare system. Telemedicine allows the assistance of patients remotely, breaking down geographical barriers.

Purpose

The aim of the present study was to assess the validity of a novel wearable system to monitor EKG, heart rate and pulse oximetry in patients with chronic cardiac diseases. The equippement included a T-shirt with electrodes and a band with a photopletimosgraphic sensor, connected to a tiny dock station (Figure 1, panel A).

Methods

We enrolled 38 patients admitted to the coronary care unit at our hospital in Italy, 71% male, mean age 67 years, mean EF 45%. The main characteristics of the sample are listed in Table 1. The system was entirely automatic. Health parameters recording started as soon as patients wore T-shirt and band. Data were transmitted by Bluetooth technology to an external control unit. Recordings could be stored or could be checked in real time from a control room. Data were compared to measurements obtained by traditional monitoring system (telemetry).

Results

The devices tested in this study showed a satisfying level of reliability in monitoring heart rate, pulse oximetry, QT interval, QRS complex duration, and onset of arrhythmic events. Indeed, the difference between traditional monitoring system and the new wearable equipment in acquiring health parameters was not statistically significant (Figure 1, panel B). However, alerts produced by arrhythmias different from atrial fibrillation were not completely reliable.

Conclusions

The most important aspect of this new equipment was the need of minimal patient’s interaction. This system was not inferior to traditional telemetry in recording health parameters.

Predictors of heart failure events detected by a multisensor implantable defibrillator algorithm

Funding Acknowledgements

Type of funding sources: None.

Background

Cardiovascular and non-cardiovascular comorbidities are common in heart failure (HF) patients and determine disease severity and prognosis. Select modern implantable defibrillators (ICDs) are equipped with multisensor algorithms for HF monitoring. The HeartLogic index combines multiple ICD-based sensor data (heart rate, heart sounds, thoracic impedance, respiration, activity), and the associated alert has proved to be a sensitive and timely predictor of impending HF decompensation in cardiac resynchronization therapy (CRT) patients.

Purpose

This analysis aims to investigate the performance of the algorithm in non-CRT patients, as well as in relation to the presence of comorbidities.

Methods

The HeartLogic feature was activated in 568 ICD patients (410 with CRT) from 26 centers. The median follow-up was 25 months [25th–75th percentile: 15-35].

Results

We recorded 1200 HeartLogic alerts (0.71 alerts per patient-year) in 370 patients. Among patient characteristics, atrial fibrillation (AF) at implantation (HR: 1.62, 95%CI: 1.27-2.07, p<0.001) and chronic kidney disease (CKD) (HR: 1.53, 95%CI: 1.21-1.93, p<0.001) independently predicted alerts. HeartLogic alerts were not associated with CRT vs. non-CRT device implantation (HR: 1.03, 95%CI: 0.82-1.30, p=0.775). Comparing the combined index and all physiologic parameters during clinically stable periods we did not notice differences between CRT and non-CRT patients. Thoracic impedance was significantly lower in CKD than non-CKD patients. (46±11ohm versus 49±10ohm; p=0.047). We found a higher S3 amplitude (0.9±0.3mG versus 0.8±0.2mG; p=0.005) and nocturnal heart rate (72±9bpm versus 66±7bpm; p<0.001), and lower S1 amplitude (2.0±0.8mG versus 2.4±0.9mG; p<0.001) in AF patients vs non-AF. These differences persisted at the time of alerts (all p<0.05). In the overall population, and in patients stratified by device type, CKD and AF, we measured significant changes of all contributing sensors (paired t-test; p<0.05) from clinically stable periods to the time of alert.

Conclusions

The burden of HeartLogic alerts appears similar between CRT and non-CRT patients, while patients with AF and CKD seem more exposed to alerts. ICD-measured thoracic impedance is sensitive to the fluid overload that characterizes kidney disease, as well as the first and third heart sound amplitudes seem sensitive to the reduced ventricular efficiency during AF. Nonetheless, ICD sensors seem to equally contribute to the HeartLogic alerts in all patient subgroups.

C64 UNMASKING THE PREVALENCE OF AMYLOID CARDIOMYOPATHY IN THE REAL WORLD: RESULTS FROM PHASE 2 OF AC–TIVE STUDY, AN ITALIAN NATIONWIDE SURVEY

Background

Clinicians need to identify patients with amyloid cardiomyopathy (AC) at an early stage, due to the availability of disease–modifying therapies. Some echocardiographic findings may rise the suspicion of AC, also in patients with mild or no symptoms, addressing second level diagnostic tests.

Aim

To investigate the prevalence of AC in consecutive patients ≥55 years undergoing clinically indicated, routine transthoracic echocardiogram in Italy and presenting echocardiographic signs suggestive of AC.

Methods

This is a prospective multicentric study conducted in Italy. It comprises two phases: 1) a recording phase consisting in a national survey on prevalence of possible echocardiographic red flags of AC in consecutive unselected patients ≥55 years undergoing routine echocardiogram (previously published) and 2) an AC diagnostic phase involving a diagnostic work–up for AC to investigate AC prevalence among patients with at least one echocardiographic red flag (herein presented). Patients that in Phase 1 presented an “AC suggestive” echocardiogram (i.e., at least one red flag of AC in hypertrophic, non–dilated left ventricles with preserved ejection fraction) underwent clinical evaluation, blood and urine tests and scintigraphy with bone tracer. Diagnosis of transthyretin related–AC (ATTR–AC) was made in presence of grade 2–3 Perugini uptake at scintigraphy and absence of monoclonal protein. The study was registered at ClinicalTrials.gov (#NCT04738266).

Results

Of the 5315 screened echocardiograms, 381 exams (7.2%) were classified as “AC suggestive” and proceeded to Phase 2. 217 patients completed Phase 2 investigations. Main reasons for the 164 non–entering patients into Phase 2 were death (n = 49) and refusal to participate (n = 66). A final diagnosis of AC was made in 62 patients with an estimated prevalence of 28,6% (95% CI: 22,5%–34,7%). ATTR–AC was diagnosed in 51 and AL–AC in 11 patients, ascertaining a prevalence of 23,5% (95% CI: 17,8%–29,2%) and 5,1% (95% CI: 2,2%–8,0%), respectively.

Conclusion

Among a cohort of consecutive unselected patients ≥55 years with echocardiographic findings suggestive of AC, the prevalence of AC ranged from 23% up to 35%. Although ATTR–AC was predominant, AL–AC was diagnosed in a significant number of cases. Echocardiography has a fundamental role in screening patients, raising the suspicion of disease and orienting diagnostic work–up for AC.

Multimodality imaging in the evaluation of left ventricle myocardial deformation determined by edema and scar in acute myocarditis

Funding Acknowledgements

Type of funding sources: None.

INTRODUCTION

acute myocarditis (aMY) is characterized by the presence of edema and myocardial scar detected by cardiovascular magnetic resonance (CMR). 

Aim of our study is to investigate the diagnostic value of two-dimensional (2D) speckle tracking echocardiography and Cardiovascular Magnetic Resonance (CMR) feature tracking (FT) in detecting edema and myocardial scar in aMY.

METHODS

all consecutive patients with clinically suspected aMY were enrolled in our study. Inclusion criteria were: 1) new ECG abnormalities 2) myocardial cytolysis markers and 3) absence of angiographically detectable coronary artery disease. Exclusion criteria included poor cine image quality caused by respiratory motion and arrhythmia. All patients underwent transthoracic echocardiography and cardiac function was evaluated by a comprehensive assessment of LV function, including 2D speckle-tracking echocardiography (2D STE). CMR was performed in all patients in a 3T scanner. Extension of edema and myocardial scar were respectively evaluated on T2 mapping and on Late Gadolinium Enhancement sequences considering numbers of segments involved according to 17-segment model (AHA). FT analysis of the left ventricle (LV) was performed using the Tissue Tracking Module to obtain LV strain data.

RESULTS

52 patients were included in the study, mean age was 36± 17 years, three patients were female (6%). Mean LVEF was 56,2 ± 7,2 % and mean end diastolic volume index (EDVi) was 62,52 ± 19,02 ml/m2. 10 patients (19,2%) had impaired EF with mean values of 44,6 ± 6,15%. aMY was confirmed in all patients with the presence of myocardial edema and subepicardial late gadolinium enhancement (LGE).  Inferior segments were involved in 28 patients (53,8%), lateral segment in 19 patients (36,5%), septal segments in 7 patients (13,5%)  and anterior segments in 15 patients (28,8%). 2D STE LV GLS was -16.41± 5,47% while CMR-FT LV GLS was -19,07 ± 4,65%, showing a good agreement between the two methods (r = 0,5; p < 0,001). The univariate analysis showed a significant correlation between 2D STE LV GLS and CMR-FT LV GLS with the extension of myocardial edema assessed by CMR (r= 0,43; p= 0,002 and r = 0.47; p = 0,002 respectively). The univariate analysis did not show a significant correlation between 2D STE LV and the extension of myocardial scar assessed by CMR (r= 0.2; p= 0.155) while a significant correlation was found between CMR-FT LV GLS and myocardial scar (r = 0.4; p = 0.01).

CONCLUSIONS

in patients with aMY, good correlation was found between CMR-FT and 2D STE in the evaluation of GLS. 2D STE LV GLS and CMR-FT LV GLS proved to have a good correlation with the extension of myocardial edema, while only CMR-FT LV GLS proved to be associated with myocardial scar extension.

48Remote monitoring of Heart Failure patients with a Multisensor ICD Algorithm: value of an alert-based follow-up strategy

Background

The HeartLogic algorithm measures and combines multiple parameters, i.e. heart sounds, intrathoracic impedance, respiration pattern, night heart rate, and patient activity, in a single index. The associated alert has proved to be a sensitive and timely predictor of impending heart failure (HF) decompensation, and the HeartLogic alert condition was shown to identify patients during periods of significantly increased risk of HF events.

Purpose

To report the results of a multicenter experience of remote HF management with HeartLogic algorithm and appraise the value of an alert-based follow-up strategy.

Methods

The HeartLogic feature was activated in 104 patients (76 male, 71 ± 10 years, left ventricular ejection fraction 29 ± 7%). All patients were followed according to a standardized protocol that included remote data reviews and patient phone contacts every month and at the time of HeartLogic alerts. In-office visits were performed every 6 months or when deemed necessary.

Results

During a median follow-up of 13[11-18] months, centers performed remote follow-up at the time of 1284 scheduled monthly transmissions (10.5 per pt-year) and 100 HeartLogic alerts (0.82 alerts/pt-year). The mean delay from alert to the next monthly remote data review was 14 ± 8 days. Overall, the patient time in the alert state (i.e. HeartLogic index above the threshold) was 14% of the total observation period. HF events requiring active clinical actions were detected at the time of 11 (0.9%) monthly remote data reviews and at 43 (43%, p < 0.001) HeartLogic alerts. Moderate to severe symptoms of HF were reported during 2% of remote visits when the patient was out of HeartLogic alert condition and during 15% of remote visits performed in alert condition (p < 0.001). Out of 100 alerts, 17 required an in-office visit and 5 a hospitalization to manage the clinical condition. Overall, 282 scheduled and 56 unscheduled in-office visits were performed during follow-up. Any HF sign (i.e. S3 gallop, rales, jugular venous distension, edema) was detected during 18% of in-office visits when the patient was out of HeartLogic alert condition and during 34% of visits performed in alert condition (p = 0.002).

Conclusions

HeartLogic alerts are frequently associated with relevant actionable HF events. Events are detected earlier and the volume of alert-driven remote follow-ups is limited when compared with a monthly remote follow-up scheme. The probability of detecting common signs and symptoms of HF at regular remote or in-office assessment is extremely low when the patient is out of HeartLogic alert state. These results support the adoption of an alert-based follow-up strategy.

855Performance of a multisensor icd algorithm in heart failure patient management

Funding Acknowledgements

No funding

Background

The HeartLogic index combines data from multiple implantable cardioverter-defibrillator (ICD)-based sensors and has proved to be a sensitive and timely predictor of impending heart failure (HF) decompensation.

Purpose

To describe a multicenter experience of remote HF management of patients who received a HeartLogic-enabled ICD or cardiac resynchronization therapy ICD (CRT-D).

Methods

The HeartLogic feature was activated in 104 patients (76 male, 71 ± 10 years, left ventricular ejection fraction 29 ± 7%). In accordance with a standardized follow-up protocol, remote data reviews and patient phone contacts were performed monthly and at the time of HeartLogic alerts (when the index crossed the nominal threshold value of 16), to assess the patient decompensation status. In-office visits were performed every 6 months or when deemed necessary.

Results

During a median follow-up of 13[11-18] months, 100 HeartLogic alerts were reported (0.82 alerts/pt-year) in 53 patients. 60 HeartLogic alerts were judged clinically meaningful (i.e. associated with worsening of HF or resulted in active clinical actions). Specifically, multiple associated conditions were reported: 45 (75%) symptoms or signs of clinical deterioration of HF, 13 (22%) discontinuations or reductions of prescribed HF therapy, 11 (18%) declines in CRT percentage (with or without new onset atrial fibrillation), 8 (13%) recurrences of previous HF events. For 48 out of 60 alerts the clinician was not previously aware of the condition. Of these, 43 alerts triggered multiple clinical actions. Alert-triggered actions were: 30 (70%) diuretic dosage increases, 15 (35%) other drug adjustments, 6 (14%) HF hospitalizations, 3 (7%) device reprogramming/revisions, 1 (2%) cardioversion, 1 (2%) patient education on therapy adherence. Out of 40 non-clinically meaningful alerts (0.33 alerts/pt-year), 8 (20%) were associated with non-HF therapy changes or interventions, 3 (8%) with pulmonary events, 29 (72%) remained unexplained. The overall number of HF hospitalizations was 16 (rate 0.13 hospitalizations/pt-year). Five HF hospitalizations were not preceded by HeartLogic alert (0.04 hospitalizations/pt-year).

Conclusions

The HeartLogic index provided clinically meaningful information and allowed to remotely identify relevant HF related clinical conditions, with a low rate of unexplained detections and undetected HF events. In this experience, remote monitoring using HeartLogic alerts allowed to drive HF care and take effective clinical actions.

Clinical implementation of cardiac resynchronization therapy-regional disparities across selected ESC member countries

Background

The present analysis aimed to estimate the penetration of cardiac resynchronization therapy (CRT) on the basis of the prevalence and incidence of eligible patients in selected European countries and in Israel.

Methods and Results

The following countries were considered: Italy, Slovakia, Greece, Israel, Slovenia, Serbia, the Czech Republic, Poland, Romania, Hungary, Ukraine, and the Russian Federation. CRT penetration was defined as the number of patients treated with CRT (CRT patients) divided by the prevalence of patients eligible for CRT. The number of CRT patients was estimated as the sum of CRT implantations in the last 5 years, the European Heart Rhythm Association (EHRA) White Book being used as the source. The prevalence of CRT indications was derived from the literature by applying three epidemiologic models, a synthesis of which indicates that 10% of heart failure (HF) patients are candidates for CRT. HF prevalence was considered to range from 1% to 2% of the general population, resulting in an estimated range of prevalence of CRT indication between 1000 and 2000 patients per million inhabitants. Similarly, the annual incidence of CRT indication, representing the potential target population once CRT has fully penetrated, was estimated as between 100 and 200 individuals per million. The results showed the best CRT penetration in Italy (47–93%), while in some countries it was less than 5% (Romania, Russian Federation, and Ukraine).

Conclusion

CRT penetration differs markedly among the countries analyzed. The main barriers are the lack of reimbursement for the procedure and insufficient awareness of guidelines by the referring physicians.

[Management of infections from cardiac implantable electronic devices: recommendations from a study panel]

Cardiac Implantable Electronic Device (CIED) infections are an emerging clinical issue. There are no national recommendations on the management of these infections, also due to the limited number of dedicated and high quality clinical studies. Therefore, researchers from southern Italian centres have decided to share the clinical experience gathered so far in this field and report practical recommendations for the diagnosis and treatment of adult patients with CIED infection or endocarditis. Here we review the risk factors, diagnostic issues (microbiological and echocardiographic) and aetiology, and describe extensively the best therapeutic approach. We also address the management of complications, follow-up after discharge and the prevention of CIED infections. In this regard, a multidisciplinary approach is fundamental to appropriately manage the initial diagnostic process and the comorbidities, to plan proper antimicrobial treatment and complete percutaneous hardware removal, with the key support of microbiology and echocardiography.

The clinical role of contrast-enhanced ultrasound in the evaluation of renal artery stenosis and diagnostic superiority as compared to traditional echo-color-Doppler flow imaging

AIM

The purpose of this study was to investigate the feasibility of contrast-enhanced ultrasound (CEUS) in the evaluation of renal artery stenosis as compared with traditional techniques: echo color Doppler (ECD) investigation and selective angiography .CEUS is a technique based on the injection of an intravascular biocompatible tracer, namely an intravenous contrast galactose microparticle suspension containing microbubbles (Levovist), that has a similar rheology to that of red blood cells, allowing quantification of renal tissue perfusion.

METHODS

A population of 120 hypertensive patients (82 men, mean age 55) with a systolic abdominal murmur and/or a diagnosis of poly-districtual atherosclerosis was studied by ECD and CEUS (Levovist). Selective angiography was performed in patients with renal artery stenosis demonstrated by one of the two ultrasonographic techniques.

RESULTS

Forty of the 120 patients in the study population showed renal artery stenosis at one of the two ultrasound techniques: ECD identified renal artery stenosis in 33 cases and CEUS in 38. Instead, selective angiography had detected renal artery stenosis in 38 patients, the same with renal artery stenosis diagnosed by CEUS. Thus, CEUS sensitivity, specificity and accuracy were similar to those of angiography while six false negatives and two false positives were obtained with ECD.

CONCLUSION

Our results suggest that this renal CEUS is a promising, new, non-invasive method for screening patients with suspected renal artery stenosis. This technique appears to be superior to traditional ECD flow imaging for diagnosing renal artery stenosis and so may be an important aid in cardiovascular diagnostics.

Prognostic role of sub-clinical hypothyroidism in chronic heart failure outpatients

BACKGROUND

It has been suggested that low thyroid hormones levels may be associated with increased mortality in patients with cardiovascular disease.

AIM

To evaluate the prognostic role of thyroid function deficiency in patients with chronic heart failure (CHF).

METHODS

We evaluated 338 consecutive outpatients with stable CHF receiving conventional therapy, all of whom underwent a physical examination, electrocardiography and echocardiography. Blood samples were drawn to assess renal function, and Na+, hemoglobin, NT-proBNPs, fT3, fT4 and TSH levels. Patients with hyperthyroidism were excluded.

RESULTS

During the follow-up (15+/-8 months), heart failure progression was observed in 79 patients (including 18 who died of heart failure after hospitalisation and six who underwent transplantation). Univariate regression analysis showed that TSH (p<0.0001), fT3 (p<0.0001), fT4 (p=0.016) and fT3/fT4 (p<0.0001) were associated with heart failure progression but multivariate analysis showed that only TSH considered as a continuous variable (p = 0.001) as well as subclinical hypothyroidism (TSH &gt 5.5 mUI/l; p=0.014) remained significantly associated with the events.

CONCLUSIONS

In CHF patients TSH levels even slightly above normal range are independently associated with a greater likelihood of heart failure progression. This supports the need for prospective studies aimed at clarifying the most appropriate therapeutic approach to sub-clinical hypothyroidism in such patients.

Impact of Closed-Loop Stimulation, overdrive pacing, DDDR pacing mode on atrial tachyarrhythmia burden in Brady-Tachy Syndrome A randomized study

AIMS

Atrial overdrive pacing algorithms increase Atrial Pacing Percentage (APP) to reduce Atrial Tachyarrhythmia (AT) recurrences in patients with Brady-Tachy Syndrome (BTS). This study aimed to compare AT burden and APP in BTS patients treated with conventional DDDR pacing, DDD+ overdrive or Closed-Loop Stimulation (CLS).

METHODS AND RESULTS

One hundred and forty-nine BTS patients were included (72 male, mean age 74+/-9), who received a dual chamber pacemaker (Philos DR or Inos 2+CLS, Biotronik GmbH, Berlin, Germany) programmed in DDD at 70min(-1). At 1-month follow-up, DDDR, DDD+ or CLS algorithms were activated according to randomization. Follow-up visits for data collection were performed at 4 and 7 months. Non parametric statistical tests (Kruskal-Wallis H-test, Dunn test, Spearman coefficient) were used to analyse not-normally-distributed samples. At 7 months, AT burden was significantly lower in CLS group (20.3+/-63.1min/day, P<0.01) compared to DDDR (56.0+/-184.0min/day) and DDD+ group (63.1+/-113.8min/day). APP was higher in CLS (89.0+/-13.2%) and in DDD+ group (97.9+/-2.7%) than in DDDR group (71.1+/-26.7%, P<0.001). The correlation found between AT burden and APP was very weak: at 7-month follow-up the Spearman coefficient was -0.29 (P=NS) in CLS, -0.52 (P<0.01) in DDD+, -0.22 (P=NS) in DDDR.

CONCLUSIONS

CLS pacing was associated with a significantly lower AT burden,compared to the other pacing algorithms. Moreover APP was significantly higher in DDD+ and in CLS mode, than in DDDR. APP weakly correlated with AT burden only in DDD+ mode, though the lowest AT burden level was obtained in the CLS group where no significant correlation was found.

Electrogram width parameter analysis in implantable cardioverter defibrillators: Influence of body position and electrode configuration

The "EGM width criterion" is a discrimination algorithm that was available in the last generation ICDs. It improved ventricular tachycardia detection by withholding inappropriate therapy deliveries in the presence of narrow QRS tachycardias. The accuracy of the algorithm depends on the optimal settings of the intracardiac EGM source, the "slew thresholds," and the "width threshold." The possible dependence of these parameters on body position may affect the detection efficacy. Whether these effects can be minimized by a proper choice of the electrode configuration used for signal analysis is still to be investigated. This study aimed to evaluate the stability of the slew threshold and width threshold obtained in the supine and orthostatic positions detected by the tip-to-ventricular coil and can-to-ventricular coil electrode configurations. Their time dependence was also evaluated at the 6-month follow-up. Fifty-eight patients who were recipients of an ICD (model Medtronic 7223cx and 7227cx) were included in the study. Changing from supine to orthostatic position caused a marked variation of slew and width thresholds (21.0 +/- 13.9 V/s and 10.1 +/- 9.6 ms, respectively) in 36% of patients with tip-to-ventricular coil and in 44% of patients with can-to-defibrillating coil (the mean slew threshold variation was in this case 17.6 +/- 15.8 V/s, while the mean width threshold variation was 18.8 +/- 21.0 ms). Width threshold variation was statistically significant (P < 0.02) with the latter electrode configuration. Slew thresholds settings changed between the 1- and 6-month follow-ups in the 75% of patients with can-to-defibrillating coil configuration and in 50% with tip-to-defibrillating coil. These time related variations were significantly larger with the tip-to-defibrillating coil configuration (P < 0.01). In conclusion, EGM width parameters may change between supine and orthostatic position and over time with tip-to-defibrillating coil configuration and can-to-defibrillating coil configuration. The former configuration was less sensitive to body position changes, but more sensitive to time related variations. These findings may be useful for optimal programming of the EGM width criterion, but if parameter programming based on these results can improve the discrimination specificity still needs to be investigated.

Heart rate variability patterns before ventricular tachycardia onset in patients with an implantable cardioverter defibrillator. Participating Investigators of ICD-HRV Italian Study Group

Time- and frequency-domain analysis of heart rate variability (HRV) has been proven effective in describing alteration of autonomic control mechanisms and in identifying patients with increased cardiac and arrhythmic mortality. Patients with implantable cardioverter defibrillators offer the opportunity to evaluate HRV patterns before ventricular tachycardia (VT) and under control conditions. We therefore analyzed time- and frequency-domain parameters of short-term HRV and power-law behavior of RR interval time series at rest, at 15 to 30 minutes, and immediately before VT. In comparison to control conditions, lower values of mean cycle length duration and total power were observed before VT. Spectral analysis indicated that the low- to high-frequency ratio was significantly higher (5.5 +/- 0.6 vs 2.8 +/- 0.3) immediately before VT than during rest. Both findings were consistent with the shift of sympathovagal balance toward sympathetic predominance and reduced vagal tone. Before VT, a more negative value of the scaling exponent beta of the power-frequency relation (-1.57 +/- 0.04 vs -1.33 +/- 0.04) also confirmed the presence of an altered HRV pattern in comparison to controls. Thus, both abnormal autonomic modulation and dynamic patterns of HRV seem to characterize the minutes before arrhythmia onset in these patients.

Efficacy of implantable cardioverter-defibrillators for the prevention of sudden death in patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy is a genetic disease associated with a risk of ventricular tachyarrhythmias and sudden death, especially in young patients.

METHODS

We conducted a retrospective multicenter study of the efficacy of implantable cardioverter-defibrillators in preventing sudden death in 128 patients with hypertrophic cardiomyopathy who were judged to be at high risk for sudden death.

RESULTS

At the time of the implantation of the defibrillator, the patients were 8 to 82 years old (mean [+/-SD], 40+/-16), and 69 patients (54 percent) were less than 41 years old. The average follow-up period was 3.1 years. Defibrillators were activated appropriately in 29 patients (23 percent), by providing defibrillation shocks or antitachycardia pacing, with the restoration of sinus rhythm; the average age at the time of the intervention was 41 years. The rate of appropriate defibrillator discharge was 7 percent per year. A total of 32 patients (25 percent) had episodes of inappropriate discharges. In the group of 43 patients who received defibrillators for secondary prevention (after cardiac arrest or sustained ventricular tachycardia), the devices were activated appropriately in 19 patients (11 percent per year). Of 85 patients who had prophylactic implants because of risk factors (i.e., for primary prevention), 10 had appropriate interventions (5 percent per year). The interval between implantation and the first appropriate discharge was highly variable but was substantially prolonged (four to nine years) in six patients. In all 21 patients with stored electrographic data and appropriate interventions, the interventions were triggered by ventricular tachycardia or fibrillation.

CONCLUSIONS

Ventricular tachycardia or fibrillation appears to be the principal mechanism of sudden death in patients with hypertrophic cardiomyopathy. In high-risk patients with hypertrophic cardiomyopathy, implantable defibrillators are highly effective in terminating such arrhythmias, indicating that these devices have a role in the primary and secondary prevention of sudden death.

Percutaneous transcatheter repositioning of displaced permanent pacemaker lead

In three patients, two with a pacemaker and one with an implantable cardioverter defibrillator, hospitalized for dislodgement of a passive fixation J-shaped atrial lead, a percutaneous transcatheter repositioning was successfully attempted thus avoiding surgical revision. This procedure, performed through the femoral vein, is easy and safe. The stability of the lead position and of the pacing and sensing parameters was confirmed 1 and 6 months after the transcatheter repositioning.

A prospective, randomized, comparison in patients between a pectoral unipolar defibrillation system and that using an additional inferior vena cava electrode

The decrease of defibrillation energy requirement would render the currently available transvenous defibrillator more effective and favor the device miniaturization process and the increase of longevity. The unipolar defibrillation systems using a single RV electrode and the pectoral pulse generator titanium shell (CAN) proved to be very efficient. The addition of a third defibrillating electrode in the coronary sinus did not prove to offer advantages and in the superior vena cava showed only a slight reduction of the defibrillation threshold (DFT). The purpose of this study was to determine whether the defibrillation efficacy of the single lead unipolar transvenous system could be improved by adding an electrode in the inferior vena cava (IVC). In 17 patients, we prospectively and randomly compared the DFT obtained with a single lead unipolar system with the DFT obtained using an additional of an IVC lead. The RV electrode, Medtronic 6936, was used as anode (first phase of biphasic) in both configurations. A 108 cm2 surface CAN, Medtronic 7219/7220 C, was inserted in a left submuscular infraclavicular pocket and used as cathode, alone or in combination with IVC, Medtronic 6933. The superior edge of the IVC coil was positioned 2-3 cm below the right atrium-IVC junction. Thus, using biphasic 65% tilt pulses generated by a 120 microF external defibrillator, Medtronic D.I.S.D. 5358 CL, the RV-CAN DFT was compared with that obtained with the RV-CAN plus IVC configuration. Mean energy DFTs were 7.8 +/- 3.6 and 4.8 +/- 1.7 J (P < 0.0001) and mean impedance 65.8 +/- 13 O and 43.1 +/- 5.5 O (P < 0.0001) with the RV-CAN and the IVC configuration, respectively. The addition of IVC significantly reduces the DFT of a single lead active CAN pectoral pulse generator. The clinical use of this biphasic and dual pathway configuration may be considered in patients not meeting implant criteria with the single lead or the dual lead RV-superior vena cava systems. This configuration may also prove helpful in the use of very small, low output ICDs, where the clinical impact of ICD generator size, longevity, and related cost may offset the problems of dual lead systems.

[Medium-term clinical experience with automatic transvenous defibrillators implanted in the chest area without subcutaneous electrodes]

From March 1992 to April 1996 a pectoral biphasic transvenous implantable cardioverter defibrillator without subcutaneous leads was implanted in 35 patients with life threatening ventricular tachyarrhythmias. Mean age was 58 +/- 9 years; 23 patients had coronary artery disease, 10 non ischemic dilated cardiomyopathy and 2 arrhythmogenic right ventricular dysplasia. All were in NYHA functional class I and II and 4 in class III: mean ejection fraction was 35 +/- 12%. The mean duration of the implantation procedure was 85 +/- 35 min. The mean defibrillation threshold, measured in 23 active-CAN devices was 8.8 +/- 5 J. There were no operative complications except in one case of transient ischemic electromechanical dissociation. The mean hospital stay from the time of implant to predischarge evaluation was 6.2 +/- 2 days. The average follow-up period was 18.5 +/- 11 months. Two patients had non sudden and non arrhythmic cardiac death in the third and sixth month, respectively. In 19 patients 171 implantable cardioverter defibrillator interventions were reported: in 5 patients five inappropriate interventions were reported and in the remaining 14 were reported: 35 ventricular fibrillation and 131 ventricular tachycardia. The short duration of the procedure, brief hospitalization with very low perioperative morbidity, high efficacy and low mid-term complications give a new image to this therapeutic option.

Syncopal sustained ventricular tachycardia in a patient with right ventricular dysplasia

A 41-year-old man was hospitalized for syncopal sustained ventricular tachycardia with left bundle branch morphology. Diagnostic screening confirmed a right ventricular dysplasia: fibrofatty replacement of myocardium on endomyocardial biopsy and severe dilation of right ventricle with no left ventricular impairment was documented. His bundle recording showed an abnormally long HV interval, and programmed ventricular stimulation induced high-rate sustained ventricular tachycardia with left bundle branch block morphology associated with reduced systolic blood pressure and dizziness. Right ventricular burst pacing proved to be effective in restoring sinus rhythm. A single lead pectoral cardioverter-defibrillator was implanted and programmed for VVI and antitachycardia pacing, as first ventricular tachycardia therapeutic intervention. During 6-month follow-up, 1 asymptomatic ventricular tachycardia recurrence terminated by antitachycardia pacing was reported by the device. The possible role of the other therapeutic options such as drugs, ablation, and surgery for this specific case is also discussed.

Transvenous defibrillator implantation in patients with persistent left superior vena cava and right superior vena cava atresia

In this report a transvenous cardioverter defibrillator implantation is described in two patients with a persistent left-sided superior vena cava and right SVC atresia. In the first case, manoeuvring of the guide wire inserted through the left subclavian vein into the SVC proved impossible, revealing a left SVC originating from the left brachiocephalic vein with an acute corner. Changing the side of implantation and inserting a CPI Endotak catheter through the right subclavian vein, the lead was easily advanced through the left SVC into the coronary sinus and then into the right atrium with the tip abutting the lateral atrial wall. Subsequent manoeuvres allowed passage of the tip of the catheter into the right ventricular apex with the proximal defibrillation coil of the Endotak lead in the low left SVC, with its distal limit at the junction with the coronary sinus. A biphasic waveform single pathway RV - > left SVC successfully defibrillated with a stored energy of 5 J. In the second patient, implantation of a transvenous Medtronic system was possible from a left infraclavicular approach. A tripolar RV coil was inserted into the right ventricle via the persistent left SVC and contiguous coronary sinus. Because of the acute angle required to enter the RV in this second case, the RV lead was looped in the right atrium in order to enter the RV in a satisfactory, albeit atypical RV location. This patient was successfully defibrillated with a 5 J monophasic waveform delivered between the RV coil, a CS/left SVC coil, and a subcutaneous patch. In conclusion, both of these patients illustrate the ability to use transvenous ICDs successfully in patients with persistent left superior vena cava although the implantation technique deviates substantially from traditional methods.

Patterns of atrioventricular conduction during postexercise recovery in patients with atrial fibrillation and Wolff-Parkinson-White syndrome

The effects of the postexercise recovery phase on the functional anterograde conduction properties of the accessory pathway (AP) were evaluated. Twenty-nine patients with Wolff-Parkinson-White (WPW) syndrome were submitted to supine maximal bicycle exercise testing. In seven patients (group I), in whom sustained atrial fibrillation (AF) could be induced by transesophageal pacing (TP), mean ventricular rate (MVR), the shortest R-R interval (SRR) between preexcited beats, and the observed percentage of preexcited beats were evaluated at rest, after each step of exercise and 2 minutes after the end of exercise. In 22 patients (group II), in whom sustained AF could not be induced, decremental TP was performed to evaluate the shortest atrial cycle length (SCL) with 1:1 conduction over AP at rest, after each step of exercise, and 2 minutes after the end of exercise. In four patients in group I, the protocol was repeated with atropine injected during the last minute of exercise. In 12 patients (three from group I and nine from group II), catecholamine plasma levels were measured at rest, at peak exercise, and during recovery. MVR was 144 +/- 20 beats/min at rest, 186 +/- 21 beats/min at peak exercise (P less than 0.001 vs rest), and 179 +/- 21 beats/min during recovery (P less than 0.001 vs rest; P less than 0.05 vs peak exercise). SRR was 289 +/- 73 msec at rest, 223 +/- 25 msec at peak exercise (P less than 0.05 vs rest), and 227 +/- 29 msec during recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

[Localization of the accessory pathways using surface ECG in Wolff-Parkinson-White syndrome]

During recent years criteria for localization of bypass tracts in the Wolff-Parkinson-White syndrome from the conventional ECG have been acquired utilizing epicardial and endocardial mapping data. The polarity of delta wave and QRS in the frontal and horizontal plane and the morphology of retrograde P waves during orthodromic reciprocating tachycardia, are the most indicative elements. An accurate analysis of QRS complexes during atrial fibrillation confirms the site of pre-excitation and could suggest the presence of 2 or more accessory pathways with sufficient spatial separation. Some criteria for identifying multiple accessory pathways are discussed.

[Transesophageal study in the diagnostic evaluation of pre-excitation]

Electrophysiologic non-invasive transesophageal testing is compared to intracardiac study in the management of patients with Wolff-Parkinson-White (WPW) syndrome. Transesophageal study can be reliably used to identify the participation of the accessory pathway in reciprocating supraventricular tachycardia and to determine the anterograde conduction properties of the accessory pathway. Using the shortest pre-excited interval during induced atrial fibrillation, or programmed and continuous atrial transesophageal stimulation can markedly reduce the need of intracardiac evaluation. The greater safety and economy of transesophageal compared to the intracardiac technique justify its wider use in preliminary screening of all WPW patients, unless ablative treatment has been clinically indicated, and in evaluating long-term drug protection against a potential deleterious ventricular response during atrial tachyarrhythmias.

Electrophysiologic evaluation of intravenous L-propionylcarnitine in man

L-propionylcarnitine, a short-chain acylcarnitine, has been shown in experimental studies to induce, during acidic and hypoxic conditions, some electrophysiological changes such as an increase of duration of the action potential and of the effective refractory period. In this study, the acute electrophysiological effects of intravenous L-propionylcarnitine (30 mg/kg in 3 min) were studied in 12 subjects with estimated normal function of the sinus node and normal parameters for atrioventricular conduction. Statistically significant changes were observed 2 min after infusion. The sinus cycle length shortened (866 +/- 138 vs 818 +/- 124 msec, P less than 0.05) while refractory periods of the atrioventricular node increased (effective by 30-50 msec in four cases; functional from 425 +/- 52 to 436 +/- 55 msec, P less than 0.05). Sinuatrial conduction time, atrial refractory periods, infranodal conduction, bundle branch, His-Purkinje system and ventricular refractoriness were unchanged. Systolic and diastolic blood pressure were also unchanged. Because of the limited effects on electrophysiological parameters, L-propionylcarnitine should be used as a metabolic drug even in patients with mild disturbances of conduction.

Transesophageal versus intracardiac atrial stimulation in assessing anterograde conduction properties of the accessory pathway in Wolff-Parkinson-White syndrome

Electrophysiologic intracardiac and noninvasive transesophageal testing, used to evaluate parameters of anterograde conduction across the accessory pathway, the refractory period and shortest atrial cycle length with 1:1 conduction over the pathway, were compared to assess the reliability of the noninvasive technique in identifying patients with Wolff-Parkinson-White syndrome, at risk of rapid ventricular response during atrial fibrillation when this arrhythmia is not inducible. Sixteen patients with Wolff-Parkinson-White syndrome were submitted both to invasive and transesophageal atrial stimulation. We evaluated both the functional and effective refractory periods of the accessory pathway, using the same drive cycle length, and the shortest cycle length with 1:1 atrioventricular conduction over the accessory pathway. There were no differences between the parameters obtained by intracardiac atrial stimulation and by transesophageal atrial stimulation. The two approaches correlated well: mean functional refractory periods of the accessory pathway were 285 +/- 42 msec and 289 +/- 32 msec, respectively (NS, r = 0.88); mean effective refractory periods of the accessory pathway were 267 +/- 41 msec and 271 +/- 32 msec, respectively (NS, r = 0.89); mean shortest cycle lengths with 1:1 conduction over the accessory pathway were 255 +/- 48 msec and 255 +/- 44 msec, respectively (NS, r = 0.94). These data demonstrate the reliability of transesophageal atrial stimulation in estimating the parameters for anterograde conduction across an accessory pathway. These results, and the already documented ability of transesophageal atrial stimulation to induce atrial fibrillation, suggest this noninvasive technique should be taken as a first approach in screening patients with Wolff-Parkinson-White syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical use of transoesophageal atrial stimulation in terminating ventricular tachycardia

This study was performed to evaluate whether transoesophageal atrial pacing could also stop ventricular tachycardias with low rates and no haemodynamic impairment. Prior to resorting to ventricular endocardial pacing, seven male patients, aged between 15 and 73 years, were treated by transoesophageal atrial pacing for 10 spontaneous episodes of sustained ventricular tachycardia at rates between 105 and 160 beats per minute, without haemodynamic impairment. When atrial pacing did not allow ventricular capture, atropine sulphate was administered. Transoesophageal atrial pacing led to ventricular capture in seven episodes, which made overdriving possible, and blocked six episodes of ventricular tachycardia. In no case did transoesophageal atrial pacing lead to an acceleration of ventricular tachycardia or to degeneration into ventricular fibrillation. Transoesophageal atrial pacing can block low-rate sustained ventricular tachycardias (less than or equal to 150 beats per minute). For low-rate sustained ventricular tachycardias without haemodynamic impairment, transoesophageal atrial pacing can thus be used as the method of choice thanks to its good ratio of risk to efficiency.

The nature and evolution of ventricular arrhythmias in acute myocardial infarction

The natural evolution of ventricular arrhythmias complicating a first episode of acute myocardial infarction has been studied in a group of 56 consecutive patients, who were admitted to the Coronary Care Unit within three hours of the onset of symptoms, and in whom drug administration (digitalis, antiarrhythmics, diuretics and heparin) was limited. Ventricular arrhythmias have been evaluated by means of Holter monitoring performed during the first 24 hours, the second 24 hours, the eighth day, the 18th day and two years after discharge when antiarrhythmic drugs has been discontinued for at least five half-lives. The overall incidence and prevalence of ventricular arrhythmias showed a steady and statistically significant reduction from the first to the eighth day, and a not statistically significant increase from the eighth to the 18th day. The latter increase was still present at the two-year follow-up. The one-by-one behaviour analysis of discharged patients delineated three different patterns: patients who presented a steady reduction in ventricular arrhythmias from the first to the 18th day (44%); patients who showed an almost constant incidence of ventricular arrhythmias during all phases of acute myocardial infarction (24%); and patients who presented both a decrease and an increase in their ventricular arrhythmias (31%). The follow-up at two years showed that the majority of patients, especially those discharged in a high Lown class, had the same arrhythmias as at their follow-up on the 18th day. Correlation of ventricular arrhythmias with the extent of the infarcted area demonstrated that only the peak and mean values of lactic dehydrogenase correlated with the severity of ventricular arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)

Usefulness of transesophageal atrial pacing in hyperkalemia-induced impulse formation and conduction disturbances

This report describes the usefulness of transesophageal atrial pacing in the treatment of five patients with hyperkalemia-induced bradycardias. Three patients had marked sinus bradycardia while the other two had a regular rhythm with QRS of left bundle branch block morphology, with no P waves visible on the surface electrocardiogram. Four patients were in chronic hemodialysis three times a week, and one had severe post-traumatic hemorrhage. In three patients, hyperkalemia had been precipitated by food intoxication. In one case the cause was unknown while, in the last case, hyperkalemia was due to rapid infusion of stored blood and solutions containing high concentrations of potassium. Transesophageal atrial pacing was performed in all cases utilizing a bipolar catheter introduced into the esophagus and a constant current generator delivering square wave pulses of 10 msec duration and 19-28 mA intensity. Atrial capture, followed by impulse conduction to the ventricles, was constant in all cases, being performed for between 15 and 35 minutes until a normal sinus rhythm was restored. The procedure was well tolerated. The advantages of this procedure as opposed to invasive ventricular pacing are discussed.

Programmed stimulation in patients with minor forms of right ventricular dysplasia

Programmed electrical stimulation (PES) was performed in 17 patients, mean age 31 +/- 8 years, with minor forms of right ventricular dysplasia diagnosed because of (1) premature ventricular beats (PVBs) of left bundle branch block (LBBB) morphology; (2) no clinical or non-invasive evidence of cardiac abnormalities; (3) angiographic evidence of right ventricular wall motion abnormalities and bioptic findings of fibro-adipose infiltration. Fifteen patients had frequent and complex PVBs while two had sustained ventricular tachycardia (VT). During PES, sustained VT was induced in 2/2 patients with spontaneous sustained VT; ventricular repetitive responses were induced in 2/15 cases (13%) with complex and frequent PVBs. In conclusion, in minor forms of right ventricular dysplasia, PES induces VT only in patients with clinical VT; on the contrary, in patients with PVBs it is only possible to induce repetitive ventricular responses in a small proportion of cases; it is therefore not possible to select patients at high risk of developing severe ventricular arrhythmias.

Electrophysiologic evaluation of intravenous nicardipine in man

The acute electrophysiological effects of intravenous nicardipine (0.014 mg/kg per min for 5 minutes) were studied in 12 subjects with estimated normal sinus node functions and atrioventricular conduction parameters. The most important effects were sinus cycle length shortening, increase of corrected sinus node recovery time and reduction of effective and functional refractory period of the atrioventricular node. Sinuatrial conduction time, atrial refractory periods, intranodal conduction, bundle branch refractoriness and ventricular refractoriness were unchanged. Systolic and diastolic blood pressure was reduced. The clinical implications of these properties of the drug are discussed and compared with those of verapamil, diltiazem and nifedipine.

Incidence of 'dual A-V nodal pathways' in first- and second-degree type I supra-His A-V block

The incidence of 'dual A-V nodal pathways', diagnosed on the basis of spontaneous or induced modifications in the PR interval, has been assessed in a group of 168 consecutive patients with first- (77) and second-degree (91) type I supra-His block. 'Dual A-V nodal pathways' were found in 12 cases (16%) with first-degree and in 7 cases (7.7%) with second-degree type I supra-His A-V block. His bundle recording confirmed the hypothesis that PR interval variations observed in these cases are due to modifications in the AH interval and thus to changes in A-V nodal conduction velocity. The electrophysiologic study also showed that the phenomenon was easily reproduced by atrial stimulation. The frequent association between 'dual A-V nodal pathways' and supra-His blocks suggests that the block mechanism should be studied in depth as it could have prognostic and therapeutic implications.

Role of QT prolongation secondary to a postextrasystolic pause as a possible mechanism for the induction of ventricular fibrillation. Report of two cases

Two patients developed ventricular fibrillation (VF) while undergoing continuous electrocardiographic monitoring. Analysis showed that VF appeared only when a particular combination of circumstances occurred: a postextrasystolic pause, QT prolongation of the subsequent beat and a premature ventricular beat that did not have a short coupling interval. The relevance of this sequence as a trigger mechanism of VF is discussed.

Ventricular fibrillation induced by transesophageal atrial pacing in hypertrophic cardiomyopathy

Sudden death is a rather frequent occurrence in patients with hypertrophic cardiomyopathy, yet the mechanism is uncertain in most cases. We describe a case of an 18 years old patient with a family history of hypertrophic cardiomyopathy and sudden death in whom ventricular fibrillation could be repeatedly induced by means of transesophageal atrial stimulation with 1:1 AV conduction at a rate of 200 beats min-1 and prevented by pharmacological depression of AV node. The not particularly high ventricular rate at which VF occurred could suggest that in hypertrophic cardiomyopathy a major role in favouring VF induction is played by the electrophysiological properties of the myocardium and that sudden death can occur as a consequence of different atrial tachyarrhythmias.