Asymptomatic versus symptomatic episodes in patients with paroxysmal atrial fibrillation via long-term monitoring with implantable loop recorders.

BACKGROUND: The presentation of atrial fibrillation (AF) varies remarkably, from totally asymptomatic to symptomatic patients, while the same individual may present symptomatic and asymptomatic episodes. We aimed to identify electrocardiographic differences between symptomatic and asymptomatic episodes and to find parameters related to the appearance of symptoms. METHODS: Thirty consecutive patients (age 66.9±10years) with paroxysmal AF received an implantable loop recorder. Three types of episodes were defined: asymptomatic (ASx), symptomatic (Sx), and mixed asymptomatic-symptomatic (AS-Sx). The heart rate (HR) and heart rate variability (HRV) were recorded during the first 2min of each ASx or Sx episode, and during the first 2min of both the symptomatic and asymptomatic periods in AS-Sx. RESULTS: Eighty-two episodes from twenty-five patients were evaluated. Mean HR was 142.48±25.84bpm for Sx and 95.71±19.29bpm for ASx (p<0.001). Mean HRV was 92.62±42.29ms for Sx and 150.06±49.68ms for ASx (p<0.001). In AS-Sx, mean HR was 102.91±24.54bpm for the asymptomatic and 141.88±23.43bpm for the symptomatic period (p<0.001). Mean HRV was 173.55±61.30ms for the asymptomatic and 87.33±30.65ms for the symptomatic period (p=0.003). There were no significant correlations between patients' characteristics and the clinical presentation of the arrhythmia. CONCLUSIONS: The ASx were characterized by a lower HR and higher HRV compared to Sx. In As-Sx, the asymptomatic period was characterized by a lower HR and higher HRV compared to the symptomatic. These findings suggest a possible contribution of variations in the autonomic nervous system activity to the perception of the arrhythmia.

Sensing issues related to the clinical use of implantable loop recorders.

AIMS: The newer insertable loop recorder device (Reveal Plus 9526, Medtronic Inc, Minneapolis MN, U.S.A.) is equipped with auto-activation capabilities. In this study we investigated whether the new device encounters sensitivity problems in the form of oversensing or undersensing. We also tested whether body position changes influence the sensed electrogram's amplitude, therefore affecting the device's autosensing ability. METHODS AND RESULTS: We enrolled 32 patients aged 58.1+/-11.7 years with a loop recorder implanted either in the left parasternal or in the heart's apex area, to investigate undiagnosed syncopal episodes after initial assessment. During the follow-up period (5.7+/-2.7 months), that began 6 months after the device implantation, we analysed 284 auto-recorded episodes (103 undersensed and 181 correctly sensed). No oversensing episodes were recorded. THE RECORDED QRS amplitude in five different body positions: supine, left and right lateral, sitting and standing was measured. No statistically significant changes were observed in the different postures. Even when patients were divided into subgroups according to implant site or the occurrence of undersensing episodes, no significant inter- or intra-group differences of the sensed electrogram were observed. CONCLUSION: Undoubtedly this device is the current gold standard for the diagnosis of unexplained syncope. In the population we studied though, the device faced undersensing problems. Consequently, the device should be equipped with more advanced software for QRS morphology recognition, to improve the diagnostic accuracy of the recorder.

Assessment of myocardial adrenergic innervation in patients with sick sinus syndrome: effect of asynchronous ventricular activation from ventricular apical stimulation.

OBJECTIVE: To investigate ventricular sympathetic innervation in patients with sick sinus syndrome and to detect regional deterioration of adrenergic innervation caused by asynchronous ventricular activation from right ventricular pacing. DESIGN: Prospective controlled study. SETTING: Tertiary cardiac referral centre. PATIENTS: 22 patients with sick sinus syndrome and indications for permanent dual chamber pacing; 20 healthy individuals as controls. INTERVENTIONS: All patients underwent myocardial imaging with planar and single photon emission computed tomography (SPECT) after an intravenous infusion of 5 mCi 123I-meta-iodobenzylguanidine (123I-MIBG) before and after pacemaker implantation. A SPECT thallium201 myocardial study was done during the same week as the 123I-MIBG study in all patients. MAIN OUTCOME MEASURES: The heart to mediastinum (H/M) ratio and washout rate were calculated during the 123I-MIBG study to assess the global cardiac sympathetic activity; the aim of the SPECT study was to investigate the regional distribution of adrenergic innervation. RESULTS: The H/M ratio was significantly smaller in the patients with sick sinus syndrome than in the controls (p < 0.001). In sick sinus syndrome there were regional adrenergic innervation defects, mostly in the inferior and apical walls. After a medium term pacing period, a redistribution of 123I-MIBG uptake was detected, with deterioration of adrenergic innervation in the inferior, apical, and posterior walls. The thallium201 myocardial perfusion study showed no change after three months of permanent pacing. CONCLUSIONS: Patients with sick sinus syndrome have global and regional disturbances of the adrenergic innervation of the left ventricular myocardium. These seem to deteriorate as a result of asynchronous electrical activation. The clinical significance of this finding requires further investigation.

Implantable loop recorder undersensing mimicking complete heart block.

The newer implantable loop recorders recently introduced (Reveal Plus. Medtronic Inc, Minneapolis, MN, U.S.A.). equipped with auto activation capabilities, are expected to expand our diagnostic abilities in the investigation of syncopal episodes. The case presented here is that of a man with pre-syncopal and syncopal episodes, without organic heart disease, in whom the device was auto-activated due to undersensing and the recorded strip imitated complete heart block. Increased attention should be given by the interpreter of the device's recordings to avoid false positive diagnoses that might lead to serious therapeutic actions.

Effect of acute atrial fibrillation on phasic coronary blood flow pattern and flow reserve in humans.

AIMS: To assess the effect of experimentally induced atrial fibrillation on coronary flow in humans. METHODS AND RESULTS: In 16 patients (10 men, mean age 43+/-13 years) with normal coronary vessels, baseline and hyperaemic blood pressure and Doppler phasic coronary flow velocity were measured, using a 0.014 inch intracoronary Doppler flow wire, during sinus rhythm, experimentally induced atrial fibrillation, and right atrial pacing at a similar heart rate to that during atrial fibrillation. Coronary flow velocity integral per minute increased significantly during both right atrial pacing and atrial fibrillation compared to sinus rhythm, but during right atrial pacing the increase was greater (85+/-43% vs 52+/-25%, P<0.001). This difference persisted even after correction for the product of heart rate and blood pressure (1.15+/-0.51 vs 0.97+/-0.46, respectively, P<0.02). In a further 12 paced patients (seven men, mean age 54+/-10 years) with complete atrioventricular block the induction of atrial fibrillation (atrial fibrillation with regular RR interval) caused no significant changes in coronary flow velocity variables. CONCLUSIONS: Acute atrial fibrillation in humans causes an increase in coronary flow that is, however, insufficient to compensate for the augmented myocardial oxygen demand, mainly because of the irregularity in the ventricular rhythm that exists during atrial fibrillation.

Effects of asynchronous ventricular activation on myocardial adrenergic innervation in patients with permanent dual-chamber pacemakers; an I(123)-metaiodobenzylguanidine cardiac scintigraphic study.

AIMS: To evaluate myocardial sympathetic innervation abnormalities in patients with DDD pacemakers for complete heart block. METHODS: We studied 39 patients, chronically paced in DDD mode because of complete atrioventricular block. Twenty-three healthy individuals served as a control group. All patients underwent planar and single-photon emission computed tomography (SPECT) myocardial imaging 4 h after intravenous infusion of 185 MBq I(123)-MIBG. The heart to mediastinum ratio was calculated to quantify cardiac I(123)-MIBG accumulation, while the SPECT study was performed to investigate the regional distribution of adrenergic innervation. All patients underwent a SPECT thallium(201)myocardial study during the same week as the I(123)-MIBG study. RESULTS: The heart to mediastinum ratio was significantly smaller in paced patients than in the controls (P<0.001). 89.7% of paced patients had regional abnormalities of I(123)-MIBG uptake, mainly in the inferior (92.3%) and apical (38.5%) wall. 46.2% of paced patients had regional perfusion defects, also mainly in the inferior (46.2%) and apical (10.3%) wall. Neither the I(123)-MIBG abnormalities nor the perfusion defects were related to the duration of pacing. CONCLUSIONS: Stimulation from the apex of the right ventricle leads to regional disturbances of the adrenergic innervation of the left ventricular myocardium, as assessed by I(123)-MIBG activity.

Electrical storm due to amiodarone induced thyrotoxicosis in a young adult with dilated cardiomyopathy: thyroidectomy as the treatment of choice.

For a patient with idiopathic dilated cardiomyopathy, an implantable defibrillator, and amiodarone induced thyrotoxicosis associated with ventricular fibrillation storm. Medical therapy was ineffective. Thyroidectomy resulted in immediate control of the arrhythmia and permitted reinitiation of amiodarone. At 18-month follow-up, the patient remained euthyroid on amiodarone and ventricular arrhythmia free.

Atrial and ventricular refractoriness in paced patients; circadian variation and its relationship to autonomic nervous system activity.

AIMS: To examine whether atrial and ventricular effective refractory periods exhibit circadian variation and whether the latter is correlated with fluctuations in autonomic nervous system tone. METHODS AND RESULTS: We studied 24 patients aged 67.1 +/- 9.6 years, 11 of whom were paced for complete heart block and 13 for sick sinus syndrome. Atrial and ventricular effective refractory periods were measured bihourly over a 24-h period, using the pacemaker programming capabilities, at basic cycle lengths of 600 ms and 500 ms. During the same time period we evaluated autonomic nervous system activity in patients paced for complete heart block, expressed by spectral power indexes in low frequency and high frequency areas of heart rate variability. Atrial and ventricular effective refractory periods showed significant circadian variation at both basic cycle lengths, with the highest values occurring between 22:00 and 06:00. At times, the atrial and ventricular effective refractory periods of the patients with sick sinus syndrome differed significantly from those with complete heart block. Furthermore, atrial and ventricular effective refractory periods in patients with complete heart block exhibited a strong negative correlation with the low frequency/high frequency ratio. CONCLUSION: Our data show that atrial and ventricular effective refractory periods in DDD paced patients exhibit significant circadian variation that is strongly correlated with variations in autonomic nervous system activity in patients with complete heart block.

Insertable loop recorder in unmasking the cause of syncope.

During the last few years closed loop recorders are being used increasingly in the investigation of unexplained syncope. Our patient had a 5-year history of pre- and syncopal episodes in which the usual invasive and noninvasive tests were nondiagnostic. Finally, a loop recorder was implanted that revealed the cause of the syncope a few days after implantation: a fast, sustained, ventricular tachycardia originating from the right ventricular outflow tract. Loop recorders will undoubtedly contribute toward the decrease in the percentage of undiagnosed syncope cases and possibly to the reduction of the investigation cost.

Low dose amiodarone and sotalol in the treatment of recurrent, symptomatic atrial fibrillation: a comparative, placebo controlled study.

OBJECTIVE: To assess and compare the safety and efficacy of amiodarone and sotalol in the treatment of patients with recurrent symptomatic atrial fibrillation. DESIGN: Prospective, randomised, single blind, placebo controlled study. SETTING: Tertiary cardiac referral centre. PATIENTS: 186 consecutive patients (97 men, 89 women; mean (SD) age, 63 (10) years) with recurrent, symptomatic atrial fibrillation. INTERVENTIONS: 65 patients were randomised to amiodarone, 61 to sotalol, and 60 to placebo. Patients receiving amiodarone were maintained at a dose of 200 mg/day after a 30 day loading phase. The sotalol dose was 160-480 mg daily, as tolerated. MAIN OUTCOME MEASURES: Recurrence of atrial fibrillation or side effects. RESULTS: In the amiodarone group, 31 of the 65 patients developed atrial fibrillation after an average of six months, while 15 (11 in sinus rhythm and four in atrial fibrillation) experienced significant side effects after an average of 16 months. In the sotalol group, relapse to atrial fibrillation occurred in 47 of the 61 patients after an average of eight months; three experienced side effects during the titration phase. In the placebo group, 53 of the 60 patients developed atrial fibrillation after an average of four months (p < 0.001 for amiodarone and sotalol v placebo; p < 0.001 for amiodarone v sotalol). CONCLUSIONS: Both amiodarone and sotalol can be used for the maintenance of normal sinus rhythm in patients with symptomatic atrial fibrillation. Amiodarone is more effective but causes more side effects.

Left ventricular diastolic filling pattern predicts cardiopulmonary determinants of functional capacity in patients with congestive heart failure.

BACKGROUND: Abnormalities of diastolic function are an important determinant of exercise intolerance in patients with heart failure. However, the relation between left ventricular filling pattern and cardiopulmonary exercise performance has not been adequately studied. METHODS: Thirty-one patients with idiopathic (n = 14) or ischemic (n = 17) dilated cardiomyopathy, demonstrated by coronary angiography, and radionuclide ejection fraction 30.5% +/- 9% underwent cardiopulmonary exercise testing with a modified Naughton protocol and a complete echocardiographic study. Patients were subdivided into restrictive and nonrestrictive groups according to their Doppler transmitral flow pattern. Gas exchange data were measured during exercise testing. The relation of left ventricular filling pattern to cardiopulmonary parameters was assessed in both groups. RESULTS: Exercise duration was similar in the restrictive and nonrestrictive groups but significant differences were found in oxygen consumption (VO(2)) at peak exercise (14.3 +/- 2.4 vs 20.4 +/- 4.7 mL/kg per minute; P <.001) and at the anaerobic threshold (VO(2AT)) (13 +/- 2.2 vs 17.3 +/- 3 mL/kg per minute; P <.001). Simple linear regression analysis revealed that both peak VO(2) and VO(2AT) were significantly correlated with the ratio of peak early (E wave) to late (A wave) transmitral filling velocity, early filling deceleration time, atrial filling fraction, and A-wave velocity but not with left ventricular ejection fraction. Multivariate regression analysis gave only the peak A-wave velocity as an independent predictor for both peak VO(2) and VO(2AT). CONCLUSIONS: In patients with heart failure, abnormalities of diastolic function are the most important determinant of exercise intolerance. A restrictive transmitral flow pattern by Doppler echocardiography is a marker of diminished cardiopulmonary exercise performance in these patients.

Amiodarone as a first-choice drug for restoring sinus rhythm in patients with atrial fibrillation: a randomized, controlled study.

STUDY OBJECTIVES: To investigate the efficacy and safety of amiodarone administered as the drug of first choice in the conversion of atrial fibrillation, regardless of its duration. DESIGN: : Prospective, randomized, controlled clinical study. SETTING: : Tertiary cardiac referral center. PATIENTS: Two-hundred eight consecutive patients (102 men; mean [+/- SD] age, 65 +/- 10 years) with atrial fibrillation. INTERVENTIONS: One-hundred eight patients received amiodarone, and 100 patients received placebo treatment. Patients randomized to amiodarone received 300 mg IV for 1 h, and then 20 mg/kg for 24 h. They were also given 600 mg/d orally, divided into three doses, for 1 week, and thereafter 400 mg/d for 3 weeks. Patients randomized to placebo treatment received an identical amount of saline solution IV over 24 h, and oral placebo treatment for 1 month. MEASUREMENTS AND RESULTS: Baseline clinical characteristics were similar in the two groups. Conversion to sinus rhythm was achieved in 87 of 108 patients (80.05%) who received amiodarone, and in 40 of 100 patients (40%) in the placebo group (p < 0.0001). Statistical analysis showed that the duration of the arrhythmia and the size of the left atrium affected both the likelihood of conversion to sinus rhythm and the time to conversion in both groups. No side effects requiring discontinuation of treatment were observed in either group. CONCLUSIONS: Amiodarone appears to be safe and effective in the termination of atrial fibrillation. However, extreme cases with a large left atrium and long-lasting arrhythmia need long-term therapy.

Autonomic nervous system activity before and during episodes of myocardial ischemia in patients with stable coronary artery disease during daily life.

Spectral analysis of heart rate variability (HRV) was used to assess changes in the autonomic nervous system (ANS) 10 minutes before, during, and 10 minutes after 110 ischemic episodes (IEs) in 38 patients (25 men, age 61 +/- 10 years) with stable coronary artery disease. In 26 of 77 diurnal IEs (07:00-22:59) there were no changes in the spectral indexes (LF and HF) during the study period. In the remainder there was an increase in the LF:HF ratio due to HF withdrawal that started before the onset of the IE. All 33 nocturnal episodes also showed an increase in the LF:HF ratio, which was due not only to HF withdrawal, but also to a simultaneous increase in LF. Although it is not the only cause, the ANS plays a significant role in triggering IEs during daily life in patients with stable coronary artery disease. The common factor in all such episodes is a gradual withdrawal of parasympathetic tone.