Search

The PIPAF trials are a set of randomized multicenter studies which seeks to evaluate the potential preventive effect of different modes of pacing in patients with drug refractory paroxysmal atrial fibrillation by means of a permanent pacemaker. The objective of the studies are (1) to significantly prolong the time to first recurrence of atrial arrhythmia and (2) to significantly reduce the cumulative arrhythmia duration. The role of the atrial pacing site (left or right), the overdriving of the sinus rate, and the suppression of the post extrasystolic compensatory pause are evaluated alone or in association, giving rise to four distinct pacing protocols. Over a period of 2 years, 220 patients will be included in 35 centers from 5 different countries.

Introduction: Despite the ability to cure atrioventricular nodal reentrant tachycardia (AVNRT) by radiofrequency catheter ablation with a high success rate, the exact localization of the tachycardia circuit is still not well established. The presence of AV nodal tissue between the typical AVNRT circuit and the His bundle, constituting a lower common pathway (LCP), remains controversial., Methods and Results: Entrainment of AVNRT during para-Hisian stimulation allows accurate measurement of the His- to- atrial (HA) interval which is part of the same circuit as that of the tachycardia. With an LCP, during tachycardia, there is simultaneous conduction from the low turnaround of the circuit to the atrium (via the fast pathway) and to the His bundle (via the LCP). However, during entrainment by para-Hisian pacing, the impulse has to retrogradely depolarize sequentially the LCP and the fast pathway. Therefore, in the presence of an LCP, the HA interval duration during tachycardia (HAt) should be shorter than that of during entrainment by para-Hisian stimulation (HAe). We considered an LCP present when Hae - HAt was > or = 10 msec. Entrainment of typical AVNRT with para-Hisian stimulation was performed in 23 consecutive patients (21 females) with a mean age of 45+/-17 years. LCP was considered to be present in 18 of 23 patients (78%). In addition, transient His-bundle dissociation from the ongoing tachycardia occurred in seven patients (30%)., Conclusion: These results support the presence of a LCP during typical AVNRT.

Cardiologists are often confronted by the situation of discussing the indications for invasive electrophysiological procedures. In this field, the recommendations of American scientific societies have been published but they are relatively dated and require updating. These procedures require the introduction of one or more catheters by a femoral venous or arterial approach, or by the endoesophageal route for positioning at different sites in the heart. The first stage of the procedure is usually to evaluate the electrophysiological properties of the cardiac chamber under investigation; followed by provocative manoeuvres such as electrical stimulation, injection of a drug, the delivery of a CEE electrical shock percutaneously or by an intracardiac radiofrequency stimulation, according to the type of procedure or the centre concerned. Schematically, the indications of these procedures may be determined in different contexts according to the benefits that may be expected in a given clinical situation. This article is devoted to the principal rhythmological situations which may be encountered but, however, the indications of radiofrequency ablation are not discussed.

Three cases of twiddler's syndrome in patients with an abdominally implanted cardioverter defibrillator (ICD) and an endocardial lead system are reported. The condition was detected when an increase in pacing threshold or lead impedance was noted at routine follow-up. Successful revision was possible in all patients; however, a recurrence in one patient necessitated removal of the device. Elderly female patients with some degree of obesity appear most susceptible. Minimizing pocket size and suturing of the device to the fascia should decrease the chance of developing this problem.

Objectives: We present three patients in whom atrial arrhythmia was treated by ablation of electrical conduction across a surgical suture line., Background: Conduction across the suture line separating the donor and native right atria has recently been described after orthotopic heart transplantation., Methods: Mapping and pacing of both grafted and recipient right atrium was performed to assess the relation between both atria and its relevance to clinical arrhythmia, prior to successful radiofrequency at the site of electrical communication., Results: In cases 1 and 3, atrioatrial conduction was bidirectional. In both, two types of P waves were observed during sinus rhythm. In case 2, conduction from the recipient to the grafted atrium yielded a very particular surface ECG pattern of atrial extrasystole. The block being unidirectional, the recipient atrial sinus rhythm was not perturbed and behaved like an atrial parasystole. Ablation was performed during sinus rhythm in case 1, recipient right atrial pacing in case 2 and grafted right atrial pacing in case 3 at the site with the shortest conduction time to the other tissue. At the successful ablation site multiple component potentials were recorded. Respectively, 1, 4 and 2 radiofrequency pulses were followed by total atrioatrial conduction interruption. No tachycardia could be induced at the end of the procedure and late follow-up was event free., Conclusions: The existence of arrhythmogenic atrioatrial conduction should be taken into account when evaluating atrial arrhythmias in the transplanted heart because it is potentially curable by radiofrequency catheter ablation.

An incessant ventricular tachycardia arising from the posterior fascicle is reported in a 29-year-old woman. This fascicular tachycardia was due to triggered activity and was clinically induced by an underlying paroxysmal atrial fibrillation. The initial echocardiographic evaluation revealed biventricular dysfunction with an ejection fraction of 30%. On propranolol, the patient has remained asymptomatic and the ventricular function has become normal after 3 months free of arrhythmia.

The French translations of the word "gap" include "hole, breach, opening". In the Anglo-saxon literature, the conduction gap or the gap phenomenon is defined as the period of the cardiac cycle during which a premature beat is blocked whereas more delayed or more premature beats are conducted. This rare phenomenon, observed mainly during extrasystolic stimulation, was previously called supernormal conduction. The underlying mechanism is distal block in the conduction system occurring when more premature beats lead to delay in the proximal conduction which gives the distal site time to become excitable again. The excitability gap is one of the main characteristics of reentrant arrhythmias. Its presence in a reentrant circuit ensures the regularity and stability of the arrhythmia. It also allows penetration of the circuit by external stimuli. This different extrasystolic stimulation technique (resetting) or rapid fixed rate pacing (entrainment) may be used diagnostically and therapeutically. It enables the identification of the arrhythmia circuit and a critical zone (protected isthmus, zone of slow conduction) which may constitute a target for ablation. It also offers a possibility for terminating the arrhythmia by external stimulation. Finally, the duration of the excitable gap may guide the choice of antiarrhythmic agent during pharmacological cardioversion of a reentrant tachycardia.

Background: Until recently no clinical studies had reported precise right atrium (RA) mapping when performing induction of atrial flutter (AFl). We studied the mode of tachycardia initiation in 16 patients (pts) referred for radiofrequency (RF) AFl ablation. AFl induction was performed at the beginning of the procedure (n = 10), or after previous AFl termination during RF delivery (n = 6). Detailed analysis of AFl initiation was provided by duodecapolar (Halo) and multipolar catheters positioned in the peritricuspidian region at the lateral right atrial wall (LRA), the inferior vena cavatricuspid annulus (IVC-TA) isthmus and the interatrial septum. Induction was obtained during incremental pacing (IAP) (15 pts) or programmed stimulation (1 pt) from the proximal coronary sinus (PCS)., Results: Atrial flutter with counterclockwise (CCW) RA rotation was induced in all pts by PCS pacing. During PCS IAP, at long pacing cycle lengths, impulse propagated in a clockwise (CW) direction through the IVC-TA isthmus and then upward at low (L) LRA. This led to a collision at the mid LRA with another wave front propagating in a CCW direction at the septum. IAP from PCS induced a progressive delay of propagation at the IVC-TA isthmus resulting in a prolongation of the PCS-Mid Isthmus interval from 85 +/- 29 to 151 +/- 42 msec. At same pacing cycle lengths (CL), the PCS-HLRA interval was comparatively less prolonged, from 75 +/- 12 to 105 +/- 18 msec, p = 0.0007. This preferential slowing of conduction between PCS and mid isthmus, during IAP from PCS, was associated with a displacement of the zone of collision to the Low LRA. Finally a CW functional block occurred at the IVC-TA isthmus and CCW AFl was induced through a period of transient concealed entrainment. The paced CL required to initiate flutter ranged from 290 to 180 msec and the mean CL of induced atrial flutter was 254 +/- 27 msec., Conclusions: The IVC-TA isthmus has decremental properties and exhibits wenckebach phenomenon during incremental PCS pacing. Initiation of a counterclockwise flutter by PCS pacing is associated with appearance of a functional unidirectional block at the IVC-TA isthmus.

Atrial fibrillation (AF) is a re-entrant rhythm, and patients with AF have intra-atrial conduction abnormalities as evidenced by prolonged P-wave duration, abnormal SAECG of P wave, fragmented atrial electrograms and greater intra-atrial conduction delays in response to APDs. Our previous work has proposed that intra-atrial conduction delays and dispersion of refractoriness during extrastimulus testing are site dependent; high right atrial (HRA) stimulation results in marked prolongation of intra-atrial conduction times and AF, whereas distal coronary sinus (CS) stimulation is associated with minimal conduction delays and absence of AF inducibility. Patients with AF induction during HRA stimulation also manifest non-uniform anisotropic conduction in the region of the posterior triangle of Koch. We postulated that if the posterior triangle of Koch is a critical area for re-entry that initiates AF, then prevention of early activation of the posterior triangle may prohibit AF induction by HRA APDs. Distal CS pacing pre-excites the posterior triangle in relation to HRA activation, therefore a subsequent HRA APD will activate the posterior triangle with a longer coupling interval. AF induction by HRA APDs following HRA pacing is prevented when same HRA APDs follow distal CS pacing. We propose that distal CS pacing eliminates the propensity of HRA extrasystoles to induce AF. This observation may have further clinical applicability in AF prevention.

Background: Atrial fibrillation (AF) is due to reentry, and its incidence has been shown to decrease after dual-site atrial or biatrial pacing. We investigated whether a simpler pacing approach via the distal coronary sinus (CSd) could eliminate AF inducibility by high right atrial (HRA) extrastimuli (APDs). We based our hypothesis on our previous observation that AF inducibility by HRA APDs was associated with conduction delays to the posterior triangle of Koch, whereas AF was never induced with CSd APDs, which were associated with minimal intra-atrial conduction delays., Methods and Results: Programmed electrical stimulation was performed from the high right atrium and CSd, and bipolar recordings were obtained from the high right atrium, His bundle, posterior triangle of Koch, and coronary sinus. In 13 patients (age, 44+/-18 years), AF was reproducibly induced with a critically timed HRA APD (220+/-22 ms) delivered during HRA pacing. AF was not induced in any of the patients when HRA APDs were delivered during CSd pacing at the same critical coupling intervals. Coronary sinus APDs delivered during HRA pacing also were not associated with AF induction. The APD coupling interval measured at the posterior triangle of Koch during CSd pacing was significantly prolonged compared with the one measured during HRA pacing and AF induction (381+/-58 versus 263+/-37 ms; P<.0001)., Conclusions: We propose that CSd pacing suppresses the propensity of HRA APDs to induce AF by limiting their prematurity at the posterior triangle of Koch and not allowing local conduction delay and local reentry to occur.

Junctional rhythm is commonly observed during radiofrequency catheter ablation of the fast or slow pathways of atrioventricular nodal reentrant tachycardia (AVNRT). However, the origin of these beats remains unclear. We analyzed the retrograde atrial activation sequence of 16 patients (mean +/- SD: 41.2 +/- 18.9 years old) undergoing catheter ablation for typical AVNRT with detailed catheter mapping of the triangle of Koch. The earliest atrial activations were concordant during tachycardia and junctional rhythm in only 5 of 16 patients. The findings suggest that junctional rhythm is unlikely to represent direct stimulation of the atrioventricular (AV) node via a discrete slow pathway but rather results from enhanced automaticity from > or =1 sites in the AV nodal transitional zone. The ensuing atrial activation pattern results from anisotropic spread from these sites. In addition, these data imply that the original concept of the AV node comprising 2 anatomically defined pathways may not be valid, and that a functionally defined pathway model may be a more accurate representation.

Background: Radiofrequency ablation of type 1 atrial flutter (AF1) has recently evolved toward an anatomically guided procedure directed to isthmuses at the lower part of the right atrium (RA). However, different types of block at these isthmuses may be observed and potentially correlated with different late outcomes. In addition, because the ablation is anatomically guided, ablation should be possible during sinus rhythm., Methods and Results: Forty-four patients underwent ablation of type 1 AF1 performed during ongoing tachycardia (33 patients) or sinus rhythm (11 patients). Evidence of inferior vena cava-tricuspid annulus isthmus block was assessed by changes in RA impulse propagation while pacing from both sides of the ablation site. Apparent complete isthmus block was achieved in 43 of 44 patients with 9 +/- 7 pulses. However, incomplete block mimicking complete block because of intra-atrial conduction delay but leading to a different low RA activation pattern was individualized. At the end of the procedure, isthmus block was complete in 35 patients and incomplete in 8, but since AF1 reinduction was no longer possible, patients were discharged. During a follow-up period of 12.1 +/- 5.5 months, 4 patients experienced AF1 recurrence; all had shown incomplete or no block., Conclusions: Detailed multiple-point low RA mapping is necessary to differentiate incomplete from complete isthmus block. Complete block is the best marker for long-term success of AF1 ablation, although incomplete block may be sufficient to prevent recurrence in a significant number of cases. Isthmus block is achievable during sinus rhythm, and AF1 induction is not mandatory.

Introduction: AV nodal reentrant tachycardia cycle length has been shown to be longer in the elderly population. Microfibrosis associated with aging producing nonuniform anisotropic conduction or changes in membrane ionic properties could explain this finding., Methods and Results: Forty-five patients (33 women and 12 men) with typical AV nodal reentrant tachycardia were studied to analyze the effects of age on electrophysiologic characteristics of the tachycardia using high-density catheter mapping of the triangle of Koch. We classified patients into group A (age < or = 45 years, mean [+/-SD] 32.7 +/- 8.8, n = 27) and group B (age > 45 years, mean [+/-SD] 61.1 +/- 10.2, n = 18). Retrograde atrial activation was recorded during tachycardia by means of a 2-mm decapolar catheter at the His bundle, a quadripolar catheter at the high right atrium, a multipolar catheter (6 to 10 poles) in the coronary sinus, and a deflectable quadripolar catheter at the posterior triangle of Koch. The AH interval at the AV junction as well as HA intervals at several atrial sites were measured during tachycardia. HA intervals at all atrial recording sites except in the posterior triangle of Koch were significantly longer in group B, as well as the tachycardia cycle length (362 vs 329 msec, P = 0.01). The mean AH interval was prolonged by 24 msec in group B, but this difference did not reach statistical significance. A sequential pattern of retrograde atrial activation during tachycardia was more frequently recorded in group B., Conclusions: Since the delayed activation to the atrium was heterogeneous, transverse nonuniform anisotropic conduction is a likely explanation of these age-related modifications of AV nodal reentrant tachycardia characteristics.

Introduction: Counterclockwise right atrial propagation is usually observed in common atrial flutter, but little is known regarding flutter with clockwise right atrial rotation. The aim of this study is to describe the ECG characteristics and results of catheter ablation of atrial flutter with clockwise right atrial rotation., Methods and Results: Among the 38 patients with type I atrial flutter in this study population, right atrial impulse propagation was counterclockwise in 20 and clockwise in 8. In the remaining 10 patients, both clockwise and counterclockwise patterns were seen. Clinical and ECG parameters associated with clockwise flutter were compared to those of 28 cases of counterclockwise atrial flutter. Ablation was performed in 11 of 18 cases using a technique identical to that used for counterclockwise flutter. A classical "sawtooth" pattern of the flutter wave was observed in 28 of 28 counterclockwise and 14 of 18 clockwise flutter. A shorter plateau phase, a widening of the negative component of the F wave in the inferior leads, and a negative F wave in V1 were the most consistent findings in clockwise flutter. Coronary sinus recording always showed septal to lateral left atrial impulse propagation. Ablation was successful in 11 of 11 cases of clockwise flutter in whom this procedure was performed, with 9.5 +/- 11.6 radiofrequency pulses delivered between the tricuspid valve and the coronary sinus ostium (n = 5) or the inferior vena cava (n = 5), and in the proximal coronary sinus (n = 1). After a follow-up of 46.6 weeks, two recurrences of clockwise flutter were encountered, which were successfully treated with a second session., Conclusion: Contrary to commonly accepted concepts, clockwise rotation of atrial flutter is not an infrequent phenomenon and can mimic counterclockwise rotation. It can also be successfully ablated by radiofrequency pulses.

Background: Selective ablation of either the fast of the slow pathway resulting in cure of AV nodal reentry tachycardia (AVNRT) has led to the concept that these pathways are discrete, anatomically defined structures. We hypothesized that if a discrete retrograde fast pathway exists, it should be possible to record a single focus of early atrial activation near the apex of Koch's triangle, with sequential spread of depolarization to the rest of the atria., Methods and Results: We evaluated 46 patients (33 women, 13 men; mean age, 45 +/- 17 years) undergoing electrophysiology study and catheter ablation for typical AVNRT. Retrograde atrial activation during AVNRT (337 +/- 43 ms) and ventricular pacing at a similar cycle length (352 +/- 51 ms) was recorded in the region of Koch's triangle with a decapolar catheter in the His bundle position, a multipolar catheter in the coronary sinus, and a deflectable quadripolar catheter along the tricuspid annulus anterior to the coronary sinus ostium. Earliest atrial activation was recorded at the apex of the triangle of Koch in 38 patients during ventricular pacing and in 43 patients during AVNRT. A broad wave front of atrial activation was recorded in 17 patients during ventricular pacing and in 26 patients during AVNRT. During AVNRT, only 2 patients had a single early site with focal and sequential activation along the tendon of Todaro. There was concordance in the pattern of atrial activation between ventricular pacing and AVNRT in only 21 of 46 patients., Conclusions: Retrograde atrial activation over the fast pathway is heterogeneous within Koch's triangle and the coronary sinus, both for the entire population and for individual patients during different modes of activation. These data do not support the concept of an anatomically discrete retrograde fast pathway.

Pulmonary extravascular water accumulation may be involved in exercise-induced hypoxaemia in highly aerobically trained athletes. We hypothesized that if such an alteration were present in elite athletes performing a maximal exercise test, the impairment of gas exchange would be worse during a second exercise test following the first one. Eight male athletes performed two incremental exercise tests separated by a 30-min recovery period. Pulmonary gas exchange and ventilatory data were measured during exercise tests performed in normoxia. Arterial blood samples were drawn each minute during rest, exercise, and recovery. Pulmonary diffusing capacity for CO (DLCO) was measured at rest, after the first (T1) and the second (T2) test. All the subjects underwent a spirometric test at rest and after T2. Maximal and recovery data for O2 uptake and minute ventilation were not statistically different between T1 and T2. Partial pressure of arterial O2 (PaO2) decreased during both tests but was lower during T2 for rest, 60 W, and 120 W (P < 0.02). Alveolar-arterial difference in partial pressure of O2 (PA-aO2) increased during both the tests but was significantly larger during T2 for rest, 60 W, and 120 W (P < 0.01). The PaO2 and PA-aO2 data at maximal exercise were not significantly different between T1 and T2. Compared to rest, PA-aO2 remained significantly larger during recovery for both T1 and T2 (P < 0.0001). The PA-aO2 during T2 recovery was larger than T1 recovery (P < 0.008). Spirometric data did not change. The DLCO measurements after T1 and T2 were not significantly different from rest. These results showed an alteration of PaO2 and PA-aO2 during T1, which tended to be worse during and after T2; however, these data do not allow us to make a definitive statement as to the cause of the hypoxaemia. Our study confirmed that exhausting exercise caused hypoxaemia. It also demonstrated that the disturbance in pulmonary gas exchange persisted for at least 30 min following the end of the exercise period and became worse during submaximal intensities of the following incremental exercise test.

Although aortic valve replacement is undoubtedly the treatment of choice for aortic valve stenosis, balloon aortic valvuloplasty may represent the only possible treatment for some frail elderly patients who may have additional medical problems. We evaluated immediate and 1-year results of balloon aortic valvuloplasty in 86 patients > or = 80 years with severe aortic stenosis. Mean age was 84 +/- 3 years. Forty-four % were 85 years or older. Mean gradient decreased from 68 to 26 mm Hg and valve area increased from 0.53 to 0.96 cm2 (P<0.05). There were two per-procedural deaths. No local vascular complication was observed. During the follow-up (13 +/- 9 months), 27 patients died, four had repeat balloon aortic valvuloplasty and eight underwent aortic valve replacement. Persistent clinical improvement was observed in 78% of the surviving patients. One-year actuarial survival rate was 73%. Balloon aortic valvuloplasty appears to be a safe and valuable technique in cases where surgery cannot be performed or carries a very high risk.

We investigated the aerobic and anaerobic contributions to performance during the Wingate test in sprint and middle-distance runners and whether they were related to the peak aerobic and anaerobic performances determined by two commonly used tests: the force-velocity test and an incremental aerobic exercise test. A group of 14 male competitive runners participated: 7 sprinters, aged 20.7 (SEM 1.3) years, competing in 50, 100 and 200-m events and 7 middle-distance runners, aged 20.0 (SEM 1.0) years, competing in 800, 1,000 and 1,500 m-events. The oxygen uptake (VO2) was recorded breath-by-breath during the test (30 s) and during the first 20 s of recovery. Blood samples for venous plasma lactate concentrations were drawn at rest before the start of the test and during the 20-min recovery period. During the Wingate test mean power (W) was determined and three values of mechanical efficiency, one individual and two arbitrary, 16% and 25%, were used to calculate the contributions of work by aerobic (Waer,ind,16%,25%) and anaerobic (Wan,ind,16%,25%) processes. Peak anaerobic power (Wan,peak) was estimated by the force-velocity test and maximal aerobic energy expenditure (Waer,peak) was determined during an incremental aerobic exercise test. During the Wingate test, the middle-distance runners had a significantly greater VO2 than the sprinters (P < 0.001), who had significantly greater venous plasma lactate concentrations (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Most pacemakers are used for the treatment of bradyarrhythmias. However, a small number of pacemakers has been implanted for the treatment of supraventricular tachycardia resistant to medical therapy. The results of small reported series show long-term pacing to be effective in terminating reentrant atrial and junctional tachycardia. This has led to an improved quality of life and fewer hospital admissions in the majority of patients. Although there are a number of limitations to the widespread use of this mode of treatment, the development of pacing techniques has improved our understanding of the mechanism of termination of tachycardia which has been fully used in ventricular tachyarrhythmias. In addition to the curative treatment of sustained junctional tachycardia, pacemakers have been implanted to prevent the occurrence of new episodes with seemingly equally satisfactory results. However, cardiac pacing for this indication is much less common now because of the very good results obtained recently by radiofrequency ablation techniques. The prevention of atrial arrhythmias, vagally-induced atrial tachyarrhythmias and the bradycardia-tachycardia syndrome are good indications for permanent pacing. The prevention of atrial fibrillation in sinus node dysfunction by pacing is becoming more popular with the emergence of new modes (DDI and rate-adjusted modes) and original arrhythmia preventing algorithms. The discussion about the real efficacy of atrial pacing in sinus node dysfunction is disappearing as results of prospective randomised trials confirming this efficacy become available, especially in preventing atrial fibrillation.

Objectives: In two patients with orthotopic heart transplantation, the surface electrocardiogram suggested interaction between the donor right atrium and the recipient right atrium. An electrophysiologic investigation was performed to assess possible atrioatrial conduction., Background: After orthotopic heart transplantation, both recipient and donor atrial activities are usually independent, but in humans they may synchronize for short periods during exercise., Methods: Electrophysiologic recordings were made using standard techniques. The atrial electrode locations (anterior for the donor and posterior for the recipient right atria) were confirmed by fluoroscopy. Incremental and programmed donor and recipient right atrial pacing protocols were performed., Results: Unidirectional conduction between native and graft atria occurred in both patients. This phenomenon was evident at rest, during normal sinus rhythm and at various pacing rates, resulting in frequent atrial bigeminy and trigeminy., Conclusions: Possible atrioatrial conduction after orthotopic heart transplantation may potentially be arrhythmogenic for the chamber where extrasystoles occur. This should be taken into account in attempting to devise new pacing modes if both atria are rendered electrically common.

We investigated the effects of a stimulation of pyruvate dehydrogenase (PDH) activity induced by 2-chloropropionate (2-CP) on venous plasma lactate concentration and peak anaerobic power (W an, peak) during periods (6 s) of incremental intense exercise, i.e. a force-velocity (F-v) test known to induce a marked accumulation of lactate in the blood. The F-v test was performed twice by six subjects according to a double-blind randomized crossover protocol: once with placebo and once with 2-CP (43 mg.kg-1 body mass). Blood samples were taken at ingestion of the drug, at 10, 20, and 40 min into the pretest period, at the end of each period of intense exercise, at the end of each 5-min recovery period, and after completion of the F-v test at 5, 10, 15, and 30 min. During the F-v test, venous plasma lactate concentrations with both placebo and 2-CP increased significantly when measured at the end of each period of intense exercise (F = 33.5, P < 0.001), and each 5-min recovery period (F = 24.6, P < 0.001). Venous plasma lactate concentrations were significantly lower with 2-CP at the end of each recovery period (P < 0.01), especially for high braking forces, i.e. 8 kg (P < 0.05), 9 kg (P < 0.02), and maximal braking force (P < 0.05). After completion of the F-v test, venous plasma lactate concentrations were also significantly lower with 2-CP (P < 0.001). The percentage of lactate decrease between 5- and 30-min recovery was significantly higher with 2-CP than with the placebo [59 (SEM 4)% vs 44.6 (SEM 5.5)%, P < 0.05]. Furthermore, W an, peak was significantly higher with 2-CP than with the placebo [1016 (SEM 60) W vs 957 (SEM 55) W, P < 0.05]. In conclusion, PDH activation by 2-CP attenuated the increase in venous plasma lactate concentration during the F-v test. Ingestion of 2-CP led to an increased W an, peak.

The ability to induce and terminate ventricular tachycardia reproducibly by programmed stimulation has led to the development of electrophysiological investigations for the management of patients suffering from spontaneous arrhythmias. The investigation consists in introducing several multipolar catheter electrodes under local anaesthesia which are then positioned in contact with the endocardium in several regions of the heart. There is no consensus as to an ideal stimulation protocol for these patients but the basic principle is the introduction of one or several ventricular extrasystoles every 8 beats in sinus rhythm or during a controlled ventricular paced rhythm. At present, the major indication is rarely diagnostic in the presence of wide QRS complex tachycardias difficult to analyse by electrocardiography. On the other hand, electrophysiological investigations are highly recommended in cases of unexplained syncope in patients with documented or suspected heart disease, in symptomatic patients with intraventricular conduction defects in whom ventricular arrhythmias are suspected as the cause of symptoms or after cardiac arrest without transmural infarction or, for many teams, after the 48th hour of transmural infarction. Electrophysiological investigations are also justified in patients in whom surgical or catheter ablation of an arrhythmogenic focus is planned because of resistance to antiarrhythmic drug therapy. Evaluation of the efficacy of antiarrhythmic drugs by repeated investigations is common in the United States but is not so widely accepted in Europe.(ABSTRACT TRUNCATED AT 250 WORDS)

Highly trained athletes (HT) have been found to show arterial hypoxaemia during strenuous exercise. A lack of compensatory hyperpnoea and/or a limitation of pulmonary diffusion by pulmonary interstitial oedema have been suggested as causes, but the exact role of each is not clear. It is known, however, that interstitial pulmonary oedema may result in rapid shallow breathing (RSB). The purpose of this study was therefore twofold: firstly, to determine the exact role of a lack of compensatory hyperpnoea versus a widened in ideal alveolar minus arterial oxygen partial pressure difference [PA(i)-aO2] in the decrease in partial pressure of oxygen in arterial blood (PaO2) and, secondly, to detect RSB during recovery in HT. Untrained subjects (UT) and HT performed exhausting incremental exercise. During rest, exercise testing, and recovery, breathing pattern, respiratory gas exchange, and arterial blood gases were measured. The PA(i)-aO2 and the difference in tidal volume (VT) between exercise and recovery for the same level of ventilation, normalized to vital capacity of the subject [delta VT(%VC)], were then calculated. A large positive delta VT(%VC) was considered to be the sign of RSB. HT showed a marked hypoxaemia (F = 11.6, P < 0.0001), higher partial pressure of carbon dioxide in arterial blood (F = 3.51, P < 0.05), and lower ideal partial pressure of oxygen in alveolar gas (P < 0.001). The relationship between PA(i)-aO2 and oxygen consumption was the same for the two groups. The widening PA(i)-aO2 persisted throughout recovery for both HT and UT. The RSB was observed in HT during recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

The aim of this study was to specify the effects of caffeine on maximal anaerobic power (Wmax). A group of 14 subjects ingested caffeine (250 mg) or placebo in random double-blind order. The Wmax was determined using a force-velocity exercise test. In addition, we measured blood lactate concentration for each load at the end of pedalling and after 5 min of recovery. We observed that caffeine increased Wmax [964 (SEM 65.77) W with caffeine vs 903.7 (SEM 52.62) W with placebo; P less than 0.02] and blood lactate concentration both at the end of pedalling [8.36 (SEM 0.95) mmol.l-1 with caffeine vs 7.17 (SEM 0.53) mmol.l-1 with placebo; P less than 0.01] and after 5 min of recovery [10.23 (SEM 0.97) mmol.l-1 with caffeine vs 8.35 (SEM 0.66) mmol.l-1 with placebo; P less than 0.04]. The quotient lactate concentration/power (mmol.l-1.W-1) also increased with caffeine at the end of pedalling [7.6.10(-3) (SEM 3.82.10(-5)) vs 6.85.10(-3) (SEM 3.01.10(-5)); P less than 0.01] and after 5 min of recovery [9.82.10(-3) (SEM 4.28.10(-5)) vs 8.84.10(-3) (SEM 3.58.10(-5)); P less than 0.02]. We concluded that caffeine increased both Wmax and blood lactate concentration.

The effect of moderate exercise on the kinetics of caffeine in 12 healthy volunteers-6 heavy coffee drinkers (HD) and 6 light coffee drinkers (LD) has been studied. Kinetics at Rest was measured first (R): the subjects remained at rest for 8 h after a single 250 mg dose of caffeine. One week later, the Exercise Kinetics (E) was measured under the same conditions, but with the subjects performing moderate exercise (30% of VO2 max) during the first hour of the study. Exercise raised the maximal plasma caffeine concentrations (R: 7.28: E: 10.45) and reduced both the half-life (R 3.99 h: E 2.29 h) and the volume of distribution (R 37 l: E 20.9 l). Both during exercise and at rest. HD had a greater half-life elimination and volume of distribution than LD. The results suggest potentiation of the effects of caffeine during exercise and an increase in its distribution due to regular heavy coffee intake.