Low energy biphasic cardioversion of atrial flutter: results from a pilot trial.

A pilot study was performed to determine the efficacy of low energy biphasic external cardioversion in common type atrial flutter. In the majority of patients (70%) successful cardioversion was achieved with low energy levels of 20 or 30 J; however a considerable number of patients (15%) were initially cardioverted to atrial fibrillation, needing an additional cardioversion with an even higher energy level.

Comparison of antero-lateral versus antero-posterior electrode position for biphasic external cardioversion of atrial flutter.

External cardioversion is an established and very important tool to terminate symptomatic atrial flutter. The superiority of the biphasic waveform has been demonstrated for atrial flutter, but whether electrode position affects the efficacy of cardioversion in this population is not known. The aim of this trial was to evaluate whether anterior-lateral (A-L) compared with anterior-posterior (A-P) electrode position improves cardioversion results. Of 130 screened patients, 96 (72 men, mean age 62 +/- 12 years) were included and randomly assigned to a cardioversion protocol with either A-L or A-P electrode position. In each group, 48 patients received sequential biphasic waveform shocks using a step-up protocol consisting of 50, 75, 100, 150, or 200 J. The mean energy (65 +/- 13 J for A-L vs 77 +/- 13 J for A-P, p = 0.001) and mean number of shocks (1.48 +/- 1.01 for A-L vs 1.96 +/- 1.00 for A-P, p = 0.001) required for successful cardioversion were significantly lower in the A-L group. The efficacy of the first shock with 50 J in the A-L electrode position (35 of 48 patients [73%]) was also highly significantly greater than the first shock with 50 J in the A-P electrode position (18 of 48 patients [36%]) (p = 0.001). In conclusion, the A-L electrode position increases efficacy and requires fewer energy and shocks in external electrical cardioversion of common atrial flutter. Therefore, A-L electrode positioning should be recommended for the external cardioversion of common atrial flutter.

Effect of electroanatomically guided versus conventional catheter ablation of typical atrial flutter on the fluoroscopy time and resource use: a prospective randomized multicenter study.

AIMS: Radiofrequency catheter ablation of typical atrial flutter is one of the most frequent indications for catheter ablation in electrophysiology laboratories today. Clinical utility of electroanatomic mapping systems on treatment results and resource utilization compared with conventional ablation has not been systematically investigated in a prospective multicenter study. METHODS AND RESULTS: In this prospective, randomized multicenter study, the results of catheter ablation to cure typical atrial flutter using conventional ablation strategy were compared with electroanatomically guided mapping and ablation (Carto). Primary endpoints of the study were procedure duration and fluoroscopy exposure time, secondary endpoints were acute success rate, recurrence rate, and resource utilization. A total of 210 patients (169 men, 41 women, mean age 63 +/- 10 years) with documented typical atrial flutter were included in the study. Acute ablation success, that is, demonstration of bidirectional isthmus block, was achieved in 99 of 105 patients (94%) in the electroanatomically guided ablation group and in 102 of 105 patients (97%) in the conventional ablation group (P > 0.05). Total procedure duration was comparable between both study groups (99 +/- 57 minutes vs 88 +/- 54 minutes, P > 0.05). Fluoroscopy exposure time was significantly shorter in the electroanatomically guided ablation group (7.7 +/- 7.3 minutes vs 14.8 +/- 11.9 minutes; P < 0.05). Total recurrence rate of typical atrial flutter at 6 months of follow-up was comparable between the 2 groups (respectively for the CARTO and conventional group 6.6% vs 5.7%, P > 0.05). The material costs per procedure in the electroanatomically guided and conventional groups (NaviStar DS vs Celsius DS) was 3035 euro (USD 3,870) and 2133 euro (USD 2,720), respectively. CONCLUSIONS: This multicenter study documented that cavotricuspid isthmus ablation to cure typical atrial flutter was highly effective and safe, both in the conventional and the electroanatomically guided ablation group. The use of electroanatomical mapping system significantly reduced the fluoroscopy exposure time by almost 50%, however, at the expense of increased cost of the procedure.

Predicting recurrence of vasovagal syncope: a simple risk score for the clinical routine.

BACKGROUND: Predictors for recurrence of syncope are lacking in patients with vasovagal syncope. The aim of this study was to identify risk factors for recurrence of syncope and develop a simple prognostic risk score of clinical value. METHODS: Two hundred seventy-six patients with a history of vasovagal syncope were prospectively followed for 2 years. Diagnosis of vasovagal syncope was based on clinical history and negative standard work-up. Inclusion in the study was independent from the result of the head-up tilt test, which was performed in all cases. Risk factors for syncope recurrence were evaluated by the Cox proportional hazards regression model and implemented in a risk score, which was validated with the log-rank test and an internal cross-validation. RESULTS: The Cox-regression analysis identified the number of previous syncopal events, history of bronchial asthma, and female gender as predictors for syncope recurrence (all P < 0.05). In contrast, head-up tilt test response had no predictive value (P = 0.881). Developing a risk score, study patients were identified as having high (recurrence rate during 2 years of follow-up: 37.2%), intermediate (24.8%), and low (6.5%) risk for syncope recurrence (receiver operating characteristic [ROC] of score 0.83, P < 0.01; Log-rank test for event-free survival, P < 0.005). CONCLUSIONS: In patients with vasovagal syncope, risk of recurrence can be stratified and is predictable based on a simple risk score.

Biphasic versus monophasic shock for external cardioversion of atrial flutter: a prospective, randomized trial.

BACKGROUND: External cardioversion is effective to terminate persistent atrial flutter. Biphasic shocks have been shown to be superior to monophasic shocks for ventricular defibrillation and atrial fibrillation cardioversion. The purpose of this trial was to compare the efficacy of rectilinear biphasic versus standard damped sine wave monophasic shocks in symptomatic patients with typical atrial flutter. METHODS: 135 consecutive patients were screened, 95 (70 males, mean age 62 +/- 13 years) were included. Patients were randomly assigned to a monophasic or biphasic cardioversion protocol. Forty-seven patients randomized to the monophasic protocol received sequential shocks of 100, 150, 200, 300 and 360 J. Forty-eight patients with the biphasic protocol received 50, 75, 100, 150 or 200 J. RESULTS: First-shock efficacy with 50-Joule, biphasic shocks (23/48 patients, 48%) was significantly greater than with the 100-Joule, monophasic waveform (13/47 patients, 28%, p = 0.04). The cumulative second-shock efficacy with the 50- and 75-Joule, biphasic waveform (39/48 patients, 81%) was significantly greater than with the 100- and 150-Joule, monophasic waveform (25/47 patients, 53%, p < 0.05). The cumulative efficacy for the higher energy levels showed naturally no significant difference between the two groups. The amount of the mean delivered energy was significantly lower in the biphasic group (76 +/- 39 J) compared to the monophasic one (177 +/- 78 J, p < 0.05). CONCLUSIONS: For transthoracic cardioversion of typical atrial flutter, biphasic shocks have greater efficacy and the mean delivered current is lower than for monophasic shocks. Therefore, biphasic cardioversion with lower starting energies should be recommended.

Stable and unstable ventricular tachycardias in patients with previous myocardial infarction: a clinically oriented strategy for catheter ablation.

OBJECTIVE: Catheter ablation of ventricular tachycardia (VT) after myocardial infarction (MI) can be complex and time-consuming. We only targeted the previously documented VTs and those with similar or longer cycle lengths. METHODS: 30 patients with VTs after MI were included in the study. Voltage mapping was performed using an electro-anatomic mapping system (CARTOT). Stable VTs were mapped during tachycardia and unstable VTs during sinus rhythm. RESULTS: Clinical VTs were stable in 16 (53%) and unstable in 14 (47%) patients, and ablation was successful in 11 (69%) and 9 patients (64%), respectively (p = 0.42). During follow-up (14 +/- 6 months), 4 patients (25%) treated for stable and 6 (43%) for unstable VTs had recurrences (p = 0.82); ablation was successful in none and 2 (33%) of them, respectively. Non-target VTs were inducible in 11 (55%) of 20 patients after successful ablation and non-inducible in 9 (45%). During follow-up, inducibility of non-target VTs did not predict recurrences (9 vs. 11%, p = 0.88). CONCLUSIONS: Catheter ablation of VTs after MI can be successfully performed. Acute success rates seem to be similar for stable and unstable VTs. VTs faster than those documented clinically exert a minor effect on VT recurrences during follow-up.

Cluster of multiple atrial tachycardias limited to pregnancy after radiofrequency ablation following senning operation.

This case report describes a female patient with a cluster of four supraventricular tachycardias during the third trimester of pregnancy. The patient was surgically corrected with a Senning operation at the age of 15. Due to numerous monomorphic atrial tachycardias at the age of 28 an ablation using the noncontact mapping system EnSite 3000 was successfully performed. She remained free of tachycardias for 2 years until the third trimester of pregnancy, where 4 electrical cardioversions and eventually a caesarean section were performed. Subsequently, the patient was free of tachycardias during a 36 month follow-up and the child is healthy.

Decennial follow-up in patients with recurrent tachycardia originating from the right ventricular outflow tract: electrophysiologic characteristics and response to treatment.

AIMS: In the setting of right ventricular outflow tract-tachycardia (RVOT-T), data about long-term follow-up (FU) with respect to the therapeutic strategies are missing. All patients (pts) referred to our institution during the last 20 years for the treatment of RVOT-T were studied in a retrospective analysis to assess mortality and efficacy of treatment. METHODS AND RESULTS: One hundred and thirty-three patients (77 female; 39+/-13 years) with sustained RVOT-T were included in this study. At the time of first presentation, diagnosis of RVOT-T was made by complete invasive and non-invasive diagnostic assessment, including electrophysiology study and two-dimensional echocardiography. After 135+/-68 months (median 136, range 29-248), patients were invited to undergo clinical assessment. Of the 133 pts, 127 (95%) survived and six (5%) died from non-cardiac disease. Anti-arrhythmic (AA) drugs were given to 62 of the 133 pts (47%); of them 32 (52%) had recurrences during follow-up. The mean time to recurrence was 10.02 years (95% CI 7.46-12.59). The other 71 study patients (53%) underwent catheter ablation. The procedure was successful in 58 pts (82%). During follow-up, 30 (52%) of the 58 successfully treated patients had recurrences of RVOT-T. The mean time to recurrence was 6.28 years (95% CI 4.96-7.6). RVOT-T recurrences were similar in morphology to those treated previously in 33% and different in 67% of cases. CONCLUSIONS: Long-term follow-up in patients with RVOT-T is favourable. Catheter ablation is effective in this setting. However, late recurrences with similar or different morphology may arise in half of the patients after initially successful treatment. AA drug therapy is a valid initial therapeutic option, since it is effective in about half of the patients.

Catheter motion during atrial ablation due to the beating heart and respiration: impact on accuracy and spatial referencing in three-dimensional mapping.

BACKGROUND: The accuracy of three-dimensional mapping systems is affected by cardiac contraction and respiration. OBJECTIVE: The study sought to determine relative motion of cardiac and thoracic structures to assess positional errors and guide the choice of an optimized spatial reference. METHODS: Motion of catheters placed at the coronary sinus (CS), pulmonary vein (PV) ostia, left atrial (LA) isthmus and roof, cavotricuspid isthmus (CTI), and right atrial appendage (RAA) were recorded for 30 patients using Ensite-NavX. The right subclavian vein, left brachiocephalic vein, azygos vein, pulmonary arteries, and a static reference were included. The displacement from a mean position was calculated for each pair of sites. Respiration effects were assessed by the shift of the motion curve during in- and expiration phases. RESULTS: The PVs showed a mean interpair displacement of 4.1 +/- 0.2 mm and a shift of 5.0 +/- 0.5 mm. Proximal CS references for all LA structures (4.0 +/- 1.1 mm) were superior to the static reference (4.9 +/- 0.7 mm; P = .01). In addition, the shift due to respiration was less pronounced at 3.5 +/- 0.8 mm versus 4.9 +/- 0.5 mm (P = .004), respectively. Motion of extracardiac vessels was influenced by a mean shift of 6.8 +/- 1 mm. The remote subclavian and brachiocephalic veins were more affected (7.6 +/- 0.7 mm) than the pulmonary arteries (5.9 +/- 0.4 mm; P = .002). For the CTI, a minimized mean displacement of less than 4.6 +/- 2.0 mm relative to the proximal CS, RAA, and azygos vein was found. CONCLUSION: Respiration is the major source of relative motion, which increases with distance from the heart. For LA procedures, a proximal CS reference position is superior to a static reference position.

Catheter ablation of multiple ventricular tachycardias after myocardial infarction guided by combined contact and noncontact mapping.

BACKGROUND: Insights gained from noncontact mapping of ventricular tachycardia (VT) have not been systematically applied to contact maps. This study sought to unify both techniques for an individualized approach to the patient with multiple ischemic VTs irrespective of cycle length. METHODS AND RESULTS: For 12 consecutive patients with chronic myocardial infarction and recurrent VT, bipolar contact maps were acquired during sinus or paced rhythm. Additional noncontact maps were obtained during 48 induced VTs (cycle length 192 to 579 ms). Endocardial exit sites were superimposed on contact maps and verified by pace-mapping. Radiofrequency lesions were extended for critical borders defined by multiple neighboring exits and followed the isovoltage contour line of contact maps. Nine critical borders were identified in 8 patients and constituted the substrate for 31 VTs. The voltage at exit sites was 0.8 mV (range 0.1 to 2.3). Noncontact maps revealed 23+/-18% of isthmus conduction. Thirty-seven (77%) of all and 83% of clinically documented VTs were rendered noninducible irrespective of cycle length by application of 27 radiofrequency lesions (range 18 to 56). Spontaneous transitions between distinct VTs along critical borders were demonstrated in 4 patients. Pace-mapping reproduced the QRS morphology of 81% of VTs and was associated with successful ablation (P<0.01). Noninducibility of any sustained VT was reached for 8 (67%) patients. During 15 months (range 5 to 28) of follow-up, 8 patients remained without recurrence, and VT episodes were reduced in the other 4 patients (P<0.01). VT cycle length was not predictive for acute or long-term success. CONCLUSIONS: The combined approach of contact and noncontact mapping effectively defines critical borders as the substrate of multiple VTs without limitation for unstable VTs.

Modulation of local Ca2+ release sites by rapid fluid puffing in rat atrial myocytes.

Atrial myocytes that lack t-tubules appear to have two functionally separate sarcoplasmic Ca2+ stores: a peripheral store associated with plasmalemmal L-type calcium channels and a central store with no apparent proximity to L-type calcium channels. Here we describe a set of calcium sparks and waves that are triggered by puffing of pressurized (200-400 mmH2O) bathing solutions onto resting isolated rat atrial myocytes. Puffing of pressurized (200 mmH2O) solutions, identical to those bathing the myocytes from distances of approximately 150 microm onto the surface of a single myocyte triggered or enhanced spontaneously occurring peripheral sparks by five- to six-fold and central Ca2+ sparks by two- to three-fold, without altering the unitary spark properties. Exposure to higher pressure flows (400 mmH2O) often triggered longitudinally spreading Ca2+ waves. These results suggest that pressurized flows may directly modulate Ca2+ signaling of atrial myocytes by activating the intracellular Ca2+ release sites.

Simultaneous mapping of activation and motion timing in the healthy and chronically ischemic heart.

BACKGROUND: Experimental data of simultaneous acquired activation and motion (AM) propagation from human subjects are not available. OBJECTIVES: The purpose of this study was to demonstrate the feasibility of a novel mapping technique allowing combined analysis of AM timing in vivo and to delineate the influence of chronically ischemic tissue on cardiac AM propagation. METHODS: Ten patients with remote myocardial infarction and 4 control patients were studied during sinus rhythm using electroanatomic mapping (CARTO). Maps of the left ventricle were obtained via the retrograde aortic approach. Real-time catheter positions were extracted using custom-made software. Catheter motion was analyzed along a static line connecting the catheter tip with the apex. Tissue Doppler measurements in all patients provided data for validation. RESULTS: Four shapes of catheter motion curves were identified and correlated to healthy tissue with variable degrees of preloading, scar tissue and dyskinetic regions, e.g. aneurysms. An analysis of the AM-delay revealed areas of delayed activation in 7, and slow motion onset in 4 patients. Tissue Doppler data correlated well with local onset of motion (correlation coefficient 0,99). CONCLUSION: Activation delays as well as long AM-intervals that can be differentiated with the described mapping technique are responsible for asynchronous contraction in the ischemic heart. Myocardial wall motion abnormalities can be derived from catheter motion curves.

Substrate modification combined with pulmonary vein isolation improves outcome of catheter ablation in patients with persistent atrial fibrillation: a prospective randomized comparison.

AIMS: To investigate the effectiveness of additional substrate modification (SM) by left atrial (LA) linear lesions as compared with pulmonary vein isolation (PVI) alone in patients with persistent atrial fibrillation (AF) in a prospective randomized study. Percutaneous PVI has evolved as an accepted treatment for paroxysmal AF but seemed to be less effective in patients with persistent AF. The benefit of PVI alone and additional linear lesions has not been validated in a randomized study so far. METHODS AND RESULTS: Sixty-two patients with persistent AF (median duration 7, range 1-18 months) were randomly assigned to either PVI alone (n = 30) or additional SM (n =32) consisting of a roof line connecting both left superior and right superior PV and LA isthmus ablation between left inferior PV and mitral annulus. Procedures including SM were performed using a three-dimensional mapping system (EnSite NavX, St Jude Medical, St Paul, MN, USA). Anti-arrhythmic drugs were discontinued within 8 weeks after ablation in both groups. Follow-up included daily trans-telephonic ECG transmitted irrespective of the patient's symptoms. PVI was successful in 98% of all targeted veins in both groups. Additional SM did not increase fluoroscopy time (72.1+/-18.7 vs. 72.9+/-17.3 min, P=0.92) because of the use of three-dimensional navigation in the PVI+SM group. AF recurrences within the first 4 weeks following ablation were more common after PVI alone (77%) than additional SM (44%, P=0.002). After a follow-up time of 487 (429-570) days, only 20% of patients undergoing stand alone PVI remained in sinus rhythm when compared with 69% following PVI combined with SM (P=0.0001). Two patients assigned to PVI+SM experienced procedure-related complications (cardiac tamponade and minor stroke) which resolved without sequelae. CONCLUSION: PVI alone is insufficient in the treatment of persistent AF. However, additional left linear lesions increase the success rate significantly. Early AF-relapses are associated with a negative outcome after PVI alone but not following additional SM.

Heparins increase endothelial nitric oxide bioavailability by liberating vessel-immobilized myeloperoxidase.

BACKGROUND: Neutrophils and monocytes are centrally linked to vascular inflammatory disease, and leukocyte-derived myeloperoxidase (MPO) has emerged as an important mechanistic participant in impaired vasomotor function. MPO binds to and transcytoses endothelial cells in a glycosaminoglycan-dependent manner, and MPO binding to the vessel wall is a prerequisite for MPO-dependent oxidation of endothelium-derived nitric oxide (NO) and impairment of endothelial function in animal models. In the present study, we investigated whether heparin mobilizes MPO from vascular compartments in humans and defined whether this translates into increased vascular NO bioavailability and function. METHODS AND RESULTS: Plasma MPO levels before and after heparin administration were assessed by ELISA in 109 patients undergoing coronary angiography. Whereas baseline plasma MPO levels did not differ between patients with or without angiographically detectable coronary artery disease (CAD), the increase in MPO plasma content on bolus heparin administration was higher in patients with CAD (P=0.01). Heparin treatment also improved endothelial NO bioavailability, as evidenced by flow-mediated dilation (P<0.01) and by acetylcholine-induced changes in forearm blood flow (P<0.01). The extent of heparin-induced MPO release was correlated with improvement in endothelial function (r=0.69, P<0.01). Moreover, and consistent with this tenet, ex vivo heparin treatment of extracellular matrix proteins, cultured endothelial cells, and saphenous vein graft specimens from CAD patients decreased MPO burden. CONCLUSIONS: Mobilization of vessel-associated MPO may represent an important mechanism by which heparins exert antiinflammatory effects and increase vascular NO bioavailability. These data add to the growing body of evidence for a causal role of MPO in compromised vascular NO signaling in humans.

Transient ST-segment-elevation during pulmonary vein ablation using circumferential coiled microelectrodes in a prospective multi-centre study.

AIMS: Paroxysmal atrial fibrillation (PAF) is predominantly triggered by focal ectopies located within the pulmonary veins (PV). The BITMAP Study (Breakthrough and Isolation Trial: Mapping and Ablation of Pulmonary Veins) investigated prospectively the safety and efficacy of a catheter design with circumferential mapping and ablation electrodes. We report the phenomenon of ST-segment-elevation during catheter placement in the left atrium (LA) and superior PVs in this multi-centre study. METHODS AND RESULTS: Forty-three patients (57+/-10 years) with PAF were included in this study. Radiofrequency catheter (RFC) ablation supported by the 4F REVELATION Helix microcatheter (Cardima Inc., Freemont, CA, USA) with eight distal-coiled microelectrodes for bipolar mapping and ablation. RFC was applied at the ostial region of PV (30 W, 45-50 degrees C) with a maximum of four RFC applications per electrode. In four of the 43 patients from three centres, we recorded the occurrence of ST-segment-elevation greater than 0.2 mV and accompanying left thoracic discomfort. The ECG changes and the symptoms started abruptly and lasted for 4.2+/-2.2 min. Pericardial effusion could instantaneously be excluded by echocardiography in all cases. Coronary angiograms were performed in three patients with the longest episodes; no thrombotic material or air emboli were present. The symptoms and the ECG changes resolved completely in all patients. CONCLUSION: The phenomenon of ST-segment-elevation during LA- and PV-mapping in patients with PAF may be a common occurrence. In this prospective multi-centre trial, we demonstrated the reversibility of this phenomenon; no cardiovascular or cerebral damage was reported during both the procedure and the follow-up. Although the mechanism is still unclear, vasospasm may contribute to this phenomenon because of autonomic dysregulation.

Correlation of symptoms to ECG diagnosis following atrial fibrillation ablation.

INTRODUCTION: Currently, definition of success following atrial fibrillation (AF) ablation is commonly based on the lack of symptoms. The purpose of this study was to evaluate the correlation between symptoms and the underlying rhythm after AF ablation. METHODS AND RESULTS: Eighty consecutive patients (pts) were treated for paroxysmal episodes of AF by segmental ostial ablation of all pulmonary veins and right atrial isthmus ablation. For 6 months pts transmitted transtelephonic (T-) ECG recordings in combination with comments daily or in the event of symptoms. Eligible comments were classified as: (1) asymptomatic, (2) symptomatic. Analysis was performed at 1-month intervals, defining an acute (first month) and chronic period (second to sixth month) after ablation. Overall 6,835 T-ECGs were analyzed. Of these 5,437 (79.5%) showed sinus rhythm (SR) and 1,398 (20.5%) showed AF. Pts in SR reported symptoms for 593 (10.9%) episodes, whereas 4,844 (89.1%) episodes were asymptomatic. During AF, 646 (46.2%) episodes were associated with symptoms, and 752 (53.8%) episodes remained asymptomatic. Exclusively asymptomatic were 7 (8.8%) pts. In 30 (52.6%) of 57 pts with AF, arrhythmic events were confined to the acute phase. Of the remaining 27 pts 14 (52%) reported an improvement, 12 (44%) the same, and 1 (4%) worsened symptoms after 3 months. A significant change (P < 0.01) toward more asymptomatic episodes from the acute (43.5%) to the chronic (57.5 +/- 4.5%) period was evident. CONCLUSION: Assessment of success after AF ablation cannot be based on the absence of symptoms due to a high prevalence of asymptomatic episodes.

Multimodality of Ca2+ signaling in rat atrial myocytes.

It has been suggested that the multiplicity of Ca(2+) signaling pathways in atrial myocytes may contribute to the variability of its function. This article reports on a novel Ca(2+) signaling cascade initiated by mechanical forces induced by "puffing" of solution onto the myocytes. Ca(i) transients were measured in fura-2 acetoxymethyl (AM) loaded cells using alternating 340- and 410-nm excitation waves at 1.2 kHz. Pressurized puffs of bathing solutions, applied by an electronically controlled micro-barrel system, activated slowly (approximately 300 ms) developing Ca(i) transients that lasted 1,693 +/- 68 ms at room temperature. Subsequent second and third puffs, applied at approximately 20 s intervals activated significantly smaller or no Ca(i) transients. Puff-triggered Ca(i) transients could be reactivated once again following caffeine (10 mM)-induced release of Ca(2+) from sarcoplasmic reticulum (SR). Puff-triggered Ca(i) transients were independent of [Ca(2+)](o), and activation of voltage-gated Ca(2+) or cationic stretch channels or influx of Ca(2+) on Na(+)/Ca(2+)exchanger, because puffing solution containing no Ca(2+), 10 microM diltiazem, 1 mM Cd(2+), 5 mM Ni(2+), or 100 microM Gd(3+) failed to suppress them. Puff-triggered Ca(i) transients were enhanced in paced compared to quiescent myocytes. Electrically activated Ca(i) transients triggered during the time course of puff-induced transients were unaltered, suggesting functionally separate Ca(2+) pools. Contribution of inositol 1,4,5-triphosphate (IP(3))-gated or mitochondrial Ca(2+) pools or modulation of SR stores by nitric oxide/nitric oxide synthase (NO/NOS) signaling were evaluated using 0.5 to 500 microM 2-aminoethoxydiphenyl borate (2-APB) and 0.1 to 1 microM carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP), and 1 mM Nomega-Nitro-L-arginine methyl ester (L-NAME) and 7-nitroindizole, respectively. Only FCCP appeared to significantly suppress the puff-triggered Ca(i) transients. It was concluded that neither Ca(2+) influx nor depolarization was required for activation of this signaling pathway. These studies suggest that pressurized puffs of solutions activate a mechanically sensitive receptor, which signals in turn the release of Ca(2+) from a limited Ca(2+) store of mitochondria. How mechanical forces are sensed and transmitted to mitochondria to induce Ca(2+) release and what role such a Ca(2+) signaling pathway plays in the physiology or pathophysiology of the heart remain to be worked out.

Efficacy and safety of radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia in the elderly.

INTRODUCTION: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common regular supraventricular tachycardia in the general population as well as in elderly patients. The purpose of the study was to investigate the success and complication rate particularly regarding the induction of an atrioventricular (AV) block by radiofrequency (RF) ablation in elderly patients with and without a preexisting AV block. METHODS AND RESULTS: Between February 1998 and July 2004, all patients with symptomatic AVNRT referred for slow-pathway ablation in our institution were included and divided into two groups: group 1 patients younger than 75 years (n = 508) and group 2 patients > or =75 years (n = 70). A preexisting prolonged PR interval was present in 17 (3.3%) patients of group 1 and in 26 (37%, P < 0.0001) patients of group 2. Following successful slow-pathway ablation (follow-up time group 1: 37 +/- 22, group 2: 37 +/- 24 months) no induction of an AV block was observed in group 2 but in four patients of group 1 (0.79%) a complete heart block was induced requiring a pacemaker implantation. In group 1, 15 (2.95%) patients with a recurrence of AVNRT were readmitted for a repeat ablation procedure. No recurrences occurred in group 2. CONCLUSION: Despite a higher incidence of preexisting prolonged PR intervals slow-pathway ablation in elderly patients is both effective and safe and should be considered as the first line therapy also in this patient population.