Thrombus formation in the left atrial appendage in the course of atrial fibrillation.

BACKGROUND: Thromboembolism in patients with nonvalvular atrial fibrillation is secondary to emboli arising from atrial cavities, particularly left atrial appendage. Stroke Prevention Atrial Fibrillation (SPAF) III study showed washing flow, left appendage ejection fraction, natural echocontrast, and left appendage volume and morphology, as risk parameters of thromboembolism. METHODS: The authors examined 69 patients by transesophageal echocardiography, subdividing them into 3 groups: 26 patients in sinus rhythm in Group A (Gr.A), 22 patients in atrial fibrillation without thrombi in the left atrial appendage in Group B (Gr.B), 21 patients with tromboembolism and with thrombus in the left atrial appendage (Gr.C). RESULTS: Atrial volume in sinus rhythm (SR) patients (41.9 +/- 23.4 cm3) was lower than the one in Gr.B (86.2 +/- 47.9 cm3, p < 0.001) and Gr.C (78.6 +/- 28.5 cm3, p < 0.01), whereas no difference was found between Gr.B and Gr.C (86.2 vs. 78.6 cm3; p > 0.05). No difference was found between Gr.A and Gr.B left atrial appendage fraction (31.8% versus 29.1%, p > 0.05), whereas it was found related to Gr.C (31.8% versus 15.4% p < 0.01). Flow velocity within left atrial appendage was significantly higher in Gr.A in relation to the other two groups (p < 0.001); flow velocity in Gr.B was lower than in Gr.A but higher than in Gr.C and in all cases such differences were statistically significant (p < 0.001). Gr.A flow duration was approximately twice as much compared to the one in Gr.B (616.8 +/- 94.1 msec vs. 483.3 +/- 172.6 msec, p < 0.01), whereas it was approximately four times higher compared to the one in Gr.C (616.8 +/- 94.1 msec vs. 165.7 +/- 53.7 msec; p < 0.001). Such duration, if related to the corresponding cardiac cycle, indicates the percentage of time during which blood flows through a cycle within the left atrial appendage; this value is about 85% of cardiac cycle in Gr.A, while it is 65% in Gr.B (p < 0.01) and about 21% in Gr.C (p < 0.001). CONCLUSIONS: Such results add a new parameter to the ones suggested in the SPAF III study for the evaluation of TE risk, that is flow duration measurement within the left atrial appendage, and its ratio to the cardiac cycle. The availability to measure this parameter, by recording the transesophageal pulse wave sample volume positioned in the atrial appendage, makes the evaluation of TE risk more reliable.

Transcatheter ablation of the accessory pathway in 2 patients with life-threatening tachyarrhythmias.

Successful transcatheter ablation of an accessory pathway in 2 patients with life-threatening tachyarrhythmias is reported. In both cases, electrophysiological evaluation documented the posterior septal location of the anomalous atrioventricular connection. Radiofrequency current energy was delivered just below the coronary sinus orifice, and resulted in disappearance of preexcitation. During the follow-up, both patients remained free from tachyarrhythmias on no medication, and serial electrocardiographic recordings confirmed the persistent absence of preexcitation. It is concluded that ablation of accessory pathways can be accomplished easily and without risk by means of the radiofrequency catheter technique. This therapeutic modality requires a short hospitalization and can be recommended as the first option in patients with the Wolff-Parkinson-White syndrome.

Curative radiofrequency catheter ablation for permanent junctional reciprocating tachycardia.

Two patients with the permanent form of junctional reciprocating tachycardia successfully treated with the radiofrequency catheter ablation technique are described. In both patients a reentrant tachycardia utilizing a concealed slow conducting posterior septal accessory pathway for retrograde conduction was demonstrated. Radiofrequency current was delivered below the coronary sinus orifice. The procedure resulted in ablation of the accessory pathway conduction in both patients. During the follow-up, both patients remained free from tachycardia on no medication. This report demonstrates that the arrhythmogenic substrate of the permanent junctional reciprocating tachycardia can be easily suppressed by means of the radiofrequency catheter technique.

Transesophageal atrial pacing in the management of re-entry supraventricular tachyarrhythmias occurring during general anesthesia.

BACKGROUND: Supraventricular tachyarrhythmias (SVTs) represent an intraoperative risk factor that should be always prevented/managed. The commonly used anti-arrhythmic drugs are accompanied by intrinsic hazards, such as pro-arrhythmic and toxic effects or unpredictable onset and duration of action. We underline the therapeutic use of transesophageal atrial pacing (TAP) for the interruption of particular re-entry SVTs occurred during surgical procedures in general anaesthesia. METHODS: Our study was carried out in 25 patients characterized by a personal clinical history of transient tachyarrhythmic episodes, subjected to general anaesthesia obtained by midazolam, propofol, N2O e O2, sevoflurane, fentanil and vecuronium bromide. We used TAP bursts of 3-5 sec, their minimal pacing rate being equivalent to the tachyarrhythmia cycle length, with an impulse intensity ranging from 18 to 25 mA. In such conditions, the re-entry was interrupted by the induction of refractoriness of the wave-front that sustained the underlying arrhythmogenic circuit. RESULTS: During the study, the following arrhythmias occurred in 7 out of all patients: 1 type I atrial flutter, 3 nodal tachycardias, 1 antidromic and 2 orthodromic atrioventricular tachycardias, respectively. TAP assured either atrial capture or prompt suppression of arrhythmias in all cases. Low intensity impulses did not ever allow ventricular capture. CONCLUSIONS: TAP can be considered as a valid therapeutic device for the management of re-entry SVTs occurred during general anaesthesia, resulting it effective, safe and easy-practicable.

Effects of propofol on the human heart electrical system: a transesophageal pacing electrophysiologic study.

Previous studies have shown that infusion of propofol has sometimes been associated with bradyarrhythmias. To evaluate the effects of propofol on the electrical system of the heart, we carried out an electrophysiologic study with transesophageal pacing on ten healthy subjects scheduled for minor elective maxillo-facial surgery. By means of atrial pacing conducted by a progressive increase in stimulation cycles, we determined, in awake patients and during propofol anesthesia (2.5 mg kg-1 for induction, followed by 100 micrograms kg-1 min-1 for maintenance), the correct sinus recovery time and the eventual appearance of Wenckebach atrio-ventricular block. We did not notice sinoatrial node depression or pathologic increase in the atrio-ventricular conduction.

Effects of remifentanil on human heart electrical system. A transesophageal pacing electrophysiological study.

AIM: Previous studies have shown that the administration of remifentanil (a micro-agonist opioid) is often accompanied by bradyarrhythmias preventable or manageable by parasympatholytic drugs. The aim of this paper is to evaluate if these negative chronotropic effects are exclusively due to an increased parasympathetic activity or to a direct action of remifentanil on heart conduction fibres. METHODS: A transesophageal pacing electrophysiological study on 40 healthy subjects scheduled for orthopaedic surgical treatment under general anaesthesia has been carried out. We determined either the correct sinus recovery time or the occurrence of Wencke-bach atrio-ventricular block in the awake state and, again, during remifentanil administration. RESULTS: In all patients either a significant depression of sino-atrial automatism or a decrease of atrio-ventricular node conduction reserve was noticed. In 2 cases, in particular, a sinus arrest and a junctional rhythm, respectively, both spontaneously recovered were observed. CONCLUSION. Atropine normalized all parameters, confirming that remifentanil-associated hypokinetic cardiac phenomena are exclusively vagally mediated.

ET-1 levels in cardioischemic patients undergoing atrial pacing.

Atrial pacing (AP) procedure was carried out in 11 cardioischemic patients to reproduce tachycardia-induced myocardial ischemia. Six control subjects underwent the same procedure until the maximum pacing rate was reached. During the procedure, endothelin-1 (ET-1) and plasma lactate levels were measured in the coronary sinus and in the aortic root. In all the patients, atrial pacing provoked electrocardiographic signs and metabolic evidence of myocardial ischemia and a significant decrease (p<0.001) in left ventricular ejection fraction. At AP-induced ischemia, coronary sinus (17.31 +/- 4.20 pg/mL) and arterial (9.60 +/- 3.31 pg/mL) ET-1 plasma levels were significantly different (p<0.001) in the patients. On the contrary, at maximum pacing rate, no significant difference (p=0.186) emerged between coronary sinus (9.72 +/- 1.09 pg/mL) and arterial (8.95 +/- 0.75 pg/mL) plasma ET-1 levels in the control group. These results suggest that, in cardioischemic patients, tachycardia can induce the coronary endothelium to release significant amounts of ET-1.