PubMed · 4740532
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
S Vaisrub. 1973-08-06. The sick sinus.. https://doi.org/10.1001/jama.225.6.632
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
BACKGROUND: A paradoxic response to atropine with development of atrioventricular (AV) block has been described in patients after heart transplantation (HTx). We investigated further the incidence and dose-response relationship of this paradoxic atropine response and explored predictive factors. METHODS: We investigated 25 clinically stable patients (age 55 +/- 2 years) 18 to 126 months after HTx. After endomyocardial biopsy, a temporary pacemaker was introduced and patients were monitored. Atropine was given in ascending doses (0.004 mg/kg body weight initially, total cumulative dose 0.035 mg/kg body weight). Physiologic tests were performed to evaluate the presence of reinnervation. RESULTS: In 20% of the patients (5/25), a paradoxic response to atropine was observed. Four patients exhibited third degree AV block, one of whom also demonstrated sinus arrest. A fifth patient showed sinus arrest only. In all patients but one, there was no ventricular escape rhythm before ventricular pacing was commenced (10 sec after block). The observed adverse effect was not correlated with the applied atropine dosage, and predisposing factors could not be identified, apart from a slightly lower resting heart rate (80 +/- 5 vs. 90 +/- 2 beats/min, P = 0.07). CONCLUSION: A significant proportion of patients respond paradoxically to atropine after HTx, leading to asystole as the result of sinus arrest or AV block. Although a plausible explanation for this effect remains speculative, our data indicate that the use of atropine or other anticholinergic drugs in patients after HTx is contraindicated.
Single chamber (SC) implantable cardioverter defibrillators (ICDs) have several limitations that might be relevant during follow-up, like atrial pacing requirements, inadequate therapies, sustained atrial tachyarrhythmias and difficulties to achieve an accurate diagnosis of the arrhythmia. Dual chamber (DC) ICDs offer an attractive and rational solution, although controversy remains if the costs and complexity of these devices offer a real clinical advantage. The Dual Chamber & Atrial Tachyarrhythmias Adverse Events Study (DATAS) was designed to analyze the ability of DC ICD, DDED, to reduce clinically significant adverse events compared with SC ICD in a non-selected population with conventional indications for ICD implantation. This is a prospective, multicentre, randomized, open labelled study, with three arms: two of them (simulated SC ICD and true DC ICD) cross-over, and the third (true SC ICD) parallels the other two. The composite primary end point comprises four Clinically Significant Adverse Events (CSAE): (1) all-cause mortality, (2) invasive intervention, hospitalization or prolongation of hospitalization due to cardiovascular cause, (3) inappropriate shocks, and (4) sustained symptomatic atrial tachyarrhythmias that (a) require urgent termination or (b) last more than 48h leading to therapeutic intervention. Secondary end points constitute each of the individual components of CSAE, cardiovascular status, quality of life and a detailed analysis of atrial and ventricular arrhythmias. To date (June 2003) there have been 343 patients enroled from 947 screened patients. The projected enrollment includes 360 patients and the conclusion of the study is expected at the beginning of 2005.
Arnold tongues are phase-locking regions in parameter space, originally studied in circle-map models of cardiac arrhythmias. They show where a periodic system responds by synchronizing to an external stimulus. Clinical studies of resting or anesthetized patients exhibit synchronization between heart-beats and respiration. Here we show that these results are successfully modeled by a circle-map, neatly combining the phenomena of respiratory sinus arrhythmia (RSA, where inspiration modulates heart-rate) and cardioventilatory coupling (CVC, where the heart is a pacemaker for respiration). Examination of the Arnold tongues reveals that while RSA can cause synchronization, the strongest mechanism for synchronization is CVC, so that the heart is acting as a pacemaker for respiration.