Impaired cardiac sympathetic innervation assessed by MIBG activity has the greatest potential for predicting cardiac death and may be useful for identifying a threshold level for selecting patients at risk for death by heart failure, sudden cardiac death, and fatal myocardial infarction.

R Re el la at ti io on ns sh hi ip p b be et tw we ee en n b br re ea at th hl le es ss sn ne es ss s a an nd d h hy yp po ox xi ic c a an nd d h hy yp pe er rc ca ap p--SThe mean value of the breathlessness at two different levels of ventilation was greater during HVR than during HCVR, suggesting that hypoxia is dyspnogenic independently of ventilatory stimulation. The HCVR was inversely correlated with the breathlessness response to ventilation, while similar correlation was partly present for HVR. The HVR was positively correlated with the breathlessness at an Sa,O 2 of 80%, whilst there was no such correlation between the HCVR and the breathlessness related to PET,CO 2 . Therefore, patients with a higher breathlessness related to increased ventilation had a lower HCVR and HVR, whilst those with a higher breathlessness with desaturation, which might include a direct influence of hypoxia, had a higher HVR.These findings suggest an interaction between ventilatory response and breathlessness during the test, which may partly include behavioural modulation of HCVR and HVR through the breathlessness in various ways, depending on the origin and nature of the sensation. Eur Respir J., 1996Respir J., , 9, 2340Respir J., -2345

Although theophylline, an adenosine receptor antagonist, is known to reduce cerebral blood flow, little clinical attention has been paid to this adverse effect. This study was designed to examine the effect of theophylline on brain tissue oxygenation for a wide range of arterial PO2 in healthy volunteers. Partial gas pressures and O2 saturation in an artery (SaO2) and the internal jugular vein (SjO2) were simultaneously measured while subjects (n = 6) were breathing room air and then exposed to two levels of isocapnic hypoxia (arterial PO2 = 60 and 45 Torr) before and after infusion of theophylline (6 mg/kg of aminophylline). For the same levels of arterial oxygenation, jugular vein PO2 markedly dropped, by 3-5 Torr, after theophylline infusion, as did SjO2, by as much as 6-10%, under the arterial PCO2, which was slightly lower by 1-2 Torr in the theophylline study. By use of the linear regression lines obtained from the relationship between SaO2 and SjO2 in each study, it was calculated that the SjO2 with theophylline, while SaO2 was 95, 90, and 80%, was comparable to that without theophylline when SaO2 was 81, 78, and 73%, respectively. On the basis of the assumption that partial gas pressures and SjO2 reflect brain tissue oxygenation, these data suggest that the effect of theophylline on brain tissue oxygenation should not be ignored in some clinical settings. The effects of chronic administration remain to be studied.

Atrial flutter and AF are complications in approximately 30% of cases of paroxysmal supraventricular tachycardia (PSVT)-indicated catheter ablation, and it is of interest to determine if therapeutic modification for PSVT would eliminate combined atrial tachyarrhythmia like atrial flutter and AF. The aim of this study was to determine the incidence and the risk of atrial tachyarrhythmias after catheter ablation of PSVT. A total of 152 patients (age range 12-74, mean 41 +/- 17 years) with accessory pathway (n = 106) and/or dual atrioventricular nodal conduction (n = 46) were enrolled in a 2-year follow-up program after successful catheter ablation. Possible risks on clinical background (age, sex, PSVT duration, hemodynamic instability during attacks), premature atrial contraction (PACs) on Holter monitoring, echocardiographic left atrial size, and electrophysiological property (insertion site, conduction type, effective refractory period) were evaluated. Atrial flutter and AF were complications in 53 (35%) of the subjects, who were elderly and had a longer PSVT history with a larger left atrial dimension and frequent PACs; however, the electrophysiological properties were similar. After a 2-year follow-up period 36 (24%) of the patients still exhibited PAC runs, including 13 (9%) with atrial flutter and AF, each one of whom were complicated with nonlethal cerebral thromboembolism and congestive heart failure. Multiplelogistic-regression analysis revealed that advanced age (> or = 41 years, P = 0.0152) and frequent PACs (> or = 1% of total daily QRS counts, P = 0.0426) on Holter monitoring are the risk factors of PAC runs and/or atrial flutter and AF. In conclusion, successful ablation for PSVT is thought to be beneficial for preventing atrial flutter and AF. However, careful follow-up to monitor for the recurrence and atrial flutter and AF related complications, especially in patients of solitary atrial flutter and AF without reciprocating tachycardia and with frequent PAC.

Hemodynamic instability is a crucial determinant of the best therapeutic option in paroxysmal supraventricular tachycardia (PSVT). However, it is still unclear if hemodynamic instability is tachycardia dependent or independent. We performed frequency-domain analysis of electrocardiographic RR variations during induced PSVT and head-up tilt tests after successful ablation to investigate the role of autonomic vasomotor function in hemodynamic instability during PSVT. Thirty-six patients with (syncope group, n = 18) and without (nonsyncope group, n = 18) syncope and/or presyncope during PSVT were enrolled in this study. Serial blood pressure, heart rate, and variations in heart rate during induced PSVT and head-up tilt tests were examined. Initial blood pressure fall and heart rate changes during induced PSVT were greater in the syncope group than in the nonsyncope group. A significant positive linear relationship was found between these two. Delayed blood pressure fall was observed in the syncope group, independent of heart rate changes. Syncope in PSVT could be predicted from the results of head-up tilt tests with 82% accuracy. Heart rate responses after isoproterenol infusion were significantly greater in the syncope group than in the nonsyncope group. The changes in low frequency to high frequency (LF:HF) values during induced PSVT and head-up tilt tests were significantly greater in the syncope group than in the nonsyncope group, and an exponential correlation was found between LF:HF changes in both tests. We conclude that PSVT rate and vasomotor reaction are related with hemodynamic instability during PSVT and head-up tilt testing is a useful method for determining if patients will have syncope during PSVT.