Antiarrhythmic and proarrhythmic effects of subcutaneous nerve stimulation in ambulatory dogs.

BACKGROUND: High output subcutaneous nerve stimulation (ScNS) remodels the stellate ganglia and suppresses cardiac arrhythmia. OBJECTIVE: The purpose of this study was to test the hypothesis that long duration low output ScNS causes cardiac nerve sprouting and increases plasma norepinephrine concentration and the duration of paroxysmal atrial tachycardia (PAT) in ambulatory dogs. METHODS: We prospectively randomized 22 dogs (11 males and 11 females) into 5 different output groups for 2 months of ScNS: 0 mA (sham) (n = 6), 0.25 mA (n = 4), 1.5 mA (n = 4), 2.5 mA (n = 4), and 3.5 mA (n = 4). RESULTS: As compared with baseline, the changes in the durations of PAT episodes per 48 hours were significantly different among different groups (sham, -5.0 ± 9.5 seconds; 0.25 mA, 95.5 ± 71.0 seconds; 1.5 mA, -99.3 ± 39.6 seconds; 2.5 mA, -155.3 ± 87.8 seconds; and 3.5 mA, -76.3 ± 44.8 seconds; P < .001). The 3.5 mA group had a greater reduction in sinus heart rate than did the sham group (-29.8 ± 15.0 beats/min vs -14.5 ± 3.0 beats/min; P = .038). Immunohistochemical studies showed that the 0.25 mA group had a significantly increased while 2.5 mA and 3.5 mA stimulation had significantly reduced growth-associated protein 43 nerve densities in both atria and ventricles. The plasma norepinephrine concentrations in the 0.25 mA group was 5063.0 ± 4366.0 pg/mL, which was significantly higher than that in the other groups of dogs (739.3 ± 946.3; P = .009). There were no significant differences in the effects of simulation between males and females. CONCLUSION: In ambulatory dogs, low output ScNS causes cardiac nerve sprouting and increases plasma norepinephrine concentration and the duration of PAT episodes while high output ScNS is antiarrhythmic.

Antiarrhythmic effects of stimulating the left dorsal branch of the thoracic nerve in a canine model of paroxysmal atrial tachyarrhythmias.

BACKGROUND: Stellate ganglion nerve activity (SGNA) precedes paroxysmal atrial tachyarrhythmia (PAT) episodes in dogs with intermittent rapid left atrial (LA) pacing. The left dorsal branch of the thoracic nerve (LDTN) contains sympathetic nerves originating from the stellate ganglia. OBJECTIVE: The purpose of this study was to test the hypothesis that high-frequency electrical stimulation of the LDTN can cause stellate ganglia damage and suppress PATs. METHODS: We performed long-term LDTN stimulation in 6 dogs with and 2 dogs without intermittent rapid LA pacing while monitoring SGNA. RESULTS: LDTN stimulation reduced average SGNA from 4.36 µV (95% confidence interval [CI] 4.10-4.62 µV) at baseline to 3.22 µV (95% CI 3.04-3.40 µV) after 2 weeks (P = .028) and completely suppressed all PAT episodes in all dogs studied. Tyrosine hydroxylase staining showed large damaged regions in both stellate ganglia, with increased percentages of tyrosine hydroxylase-negative cells. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay showed that 23.36% (95% CI 18.74%-27.98%) of ganglion cells in the left stellate ganglia and 11.15% (95% CI 9.34%-12.96%) ganglion cells in the right stellate ganglia were positive, indicating extensive cell death. A reduction of both SGNA and heart rate was also observed in dogs with LDTN stimulation but without rapid LA pacing. Histological studies in the 2 dogs without intermittent rapid LA pacing confirmed the presence of extensive stellate ganglia damage, along with a high percentage of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells. CONCLUSION: LDTN stimulation damages both left and right stellate ganglia, reduces left SGNA, and is antiarrhythmic in this canine model of PAT.

Influence of advancing age on clinical presentation, treatment efficacy and safety, and long-term outcome of inducible paroxysmal supraventricular tachycardia without pre-excitation syndromes: A cohort study of 1960 patients included over 25 years.

AIM: To investigate the influence of increasing age on clinical presentation, treatment and long-term outcome in patients with inducible paroxysmal supraventricular tachycardia (SVT) without pre-excitation syndromes. METHODS: Clinical and electrophysiological study (EPS) data, as well as long-term clinical outcome (mean follow-up 2.4±4.0 years) were collected in patients referred for regular tachycardia with inducible SVT during EPS without pre-excitation. RESULTS: Among 1960 referred patients, 301 patients (15.4%) were aged ≥70 (70-97). In this subset, anticoagulants were prescribed in 49 patients following an erroneous diagnosis of atrial tachycardia and 14 were previously erroneously diagnosed with ventricular tachycardia because of wide QRS. Ablation was performed more frequently in patients ≥70 despite more frequent failure and complications. During follow-up, higher risks of AF, stroke, pacemaker implantation and death were observed in patients ≥70 whereas SVT recurrences were similar in both age groups. In multivariable analysis, age ≥70 was independently associated with higher risks of SVT-related adverse events prior to ablation (OR = 1.93, 1.41-2.62, p<0.001), conduction disturbances (OR = 11.27, 5.89-21.50, p<0.001), history of AF (OR = 2.18, 1.22-3.90, p = 0.009) and erroneous diagnosis at baseline (OR = 9.14, 5.93-14.09, p<0.001) as well as high rates of procedural complications (OR = 2.13, 1.19-3.81, p = 0.01) and ablation failure (OR = 1.68, 1.08-2.62, p = 0.02). In contrast, age ≥70 was not significantly associated with a higher risk of AF in multivariable analysis. CONCLUSIONS: A sizeable proportion of patients with inducible SVT without pre-excitation syndromes are elderly. These patients exhibit higher risks of erroneous tachycardia diagnosis prior to EPS as well as failure and/or complication of ablation, but similar risk of SVT recurrence. These results support performing transesophageal EPS in most patients and intracardiac EPS in selected patients. EPS may furthermore prove useful in elderly patients with regular tachycardia, mainly by avoiding treatment based on an erroneous diagnosis.

Taquicardia paroxística supraventricular (TPSV): dos presentaciones. Dos aproximaciones / Paroxysmal supraventricular tachycardia (PSVT): two presentations. Two approaches

No disponible

Modified carotid sinus massage using an ultrasonography for maximizing vagal tone: a crossover simulation study.

INTRODUCTION: The aim of this study was to ascertain if a modified carotid sinus massage (CSM) using ultrasonography is superior to the conventional CSM for vagal tone generation. METHODS: This was a prospective, crossover, clinical trial including 30 subjects with sinus rhythm. Participants were paired, and they performed 2 types of CSM to each other. To perform the conventional technique, pressure was exerted at the point where the maximal impulse of the carotid pulse was palpated. In the modified technique, participants localized the point of maximal diameter just above the bifurcation of the common carotid artery using ultrasonography and applied pressure to that point. Mean differences between premaneuver and postmaneuver R-R intervals and heart rates were compared. The distance from the midline of the neck (x distance) to the angle of the mandible (y distance) was measured, and the mean distance between the 2 techniques was compared. RESULTS: The baseline mean premaneuver R-R interval and heart rate did not differ significantly between the 2 techniques. The postmaneuver R-R interval and heart rate as well as the mean R-R interval and heart rate differences were significantly greater in the modified CSM. The mean location determined using the modified CSM was located 0.8 cm lateral and 0.8 cm superior to the mean location of the conventional CSM. CONCLUSION: The modified CSM using ultrasonography might be more useful than the conventional CSM in reverting episodes of paroxysmal supraventricular tachycardia and may be a suitable alternative for treating the same in the emergency department.

Left atrial pressure and dominant frequency of atrial fibrillation in humans.

BACKGROUND: Atrial stretch is thought to play a role in the development of atrial fibrillation (AF). However, the precise mechanism by which stretch contributes to AF maintenance in humans is unknown. OBJECTIVE: The purpose of this study was to determine the impact of left atrial (LA) pressure on AF frequency in patients undergoing catheter ablation of AF. METHODS: The subjects of this study were 58 consecutive patients with persistent AF (n = 40) or paroxysmal AF (n = 18) undergoing LA ablation. LA pressure was measured before ablation. Both atria and the coronary sinus were mapped, and regional dominant frequency (DF) was determined. RESULTS: Mean LA pressure in the persistent AF group was significantly higher than in the paroxysmal AF group (18 ± 5 vs 10 ± 4 mmHg, P <.0001). Mean DF in the persistent AF group was also higher than in the paroxysmal AF group (6.36 ± 0.51 Hz and 5.83 ± 0.54 Hz, P = .0006). In patients with persistent AF, there was a significant correlation between LA pressure and DF at the LA appendage (r = 0.55, P = .0002). DF(max) was found at the LA appendage region in 24 (60%) of the 40 patients with persistent AF (P = .0006). In multivariate analysis, LA pressure was the only independent predictor of DF(max) in the LA appendage (P = .04, odds ratio 1.41, 95% confidence interval 1.02-1.94). CONCLUSION: Higher LA pressure in patients with persistent AF implies that these patients are more vulnerable to stretch-related remodeling than are patients with paroxysmal AF. The DF of AF was directly related to LA pressure in patients with persistent AF. This finding suggests that atrial stretch may contribute to the maintenance of AF in humans by stabilizing high-frequency sources.

Treatment of paroxysmal supraventricular tachycardia using instrument-assisted manipulation of the fourth rib: a 6-year case study.

OBJECTIVE: The purpose of this case report was to describe the observation of the manipulation of the fourth rib followed by the reproducible, rapid return of heart rate to normal in a patient with paroxysmal supraventricular tachycardia. CLINICAL FEATURES: A male patient had paroxysmal supraventricular tachycardia. He was evaluated using standard methods of palpation. He was followed over a 6-year period. INTERVENTION AND OUTCOME: The patient was treated during episodes of supraventricular tachycardia (SVT) with instrument-assisted manipulation of the fourth rib without treatment of any other segments. Tachycardia was eliminated after rib manipulation within less than 2 minutes. Over a 6-year period, effective control of episodes of SVT was consistently achieved associated with manipulation of the fourth rib. CONCLUSIONS: This case study is suggestive of a relationship between SVT and misalignment of the fourth rib. Controlled studies are necessary to validate this observation.

[Wide QRS complex tachycardia in a patient after inferior myocardial infarction and CABG -- the role of electrophysiological study and RF ablation]. / Czestoskurcz z szerokimi zespolami QRS u pacjenta po zawale serca i pomostowaniu aortalno-wiencowym - rola badania elektrofizjologicznego i ablacji RF.

We present a case of 53-year-old patient who experienced paroxysms of wide QRS complex tachycardia at a rate of 150 bpm and LBBB morphology 6 years after inferior myocardial infarction and CABG. Anamnesis and morphology of tachycardia could suggest ventricular tachycardia. However during electrophysiological study we observed AVRT with LBBB and "regularly irregular" AVRT with normal QRS complex and changing entrance to the AV node (through slow and fast pathway). In this paper we present our approach and try to explain why the tachycardia using concealed bypass tract appeared so late in life.

[Clinical observation on wrist-ankle acupuncture for treatment of paroxysmal supraventricular tachycardia].

OBJECTIVE: To observe the therapeutic effect and prognosis of wrist-ankle acupuncture for treatment of paroxysmal supraventricular tachycardia. METHODS: Ninety-five cases of paroxysmal supraventricular tachycardia were randomly divided into a wrist-ankle acupuncture group (n = 55) and a control group (n = 40). The treatment group were treated with acupuncture at the points, Wanshang No. 1 and 2, and the control group with oral administration of diltiazem. After being treated for 3 courses, their therapeutic effects were evaluated. RESULTS: The total effective rate was 81.8% in the treatment group and 54.0% in the control group with a significant difference between the two groups (P < 0. 05); the long-term therapeutic effect in the treatment group was better than that in the control group. CONCLUSION: Wrist-Ankle acupuncture has obvious therapeutic effect on paroxysmal supraventricular tachycardia.

Heart rate is a predictor of success in the treatment of adults with symptomatic paroxysmal supraventricular tachycardia.

AIMS: To analyse whether heart rate may affect the efficacy of adenosine, verapamil and carotid sinus massage in terminating symptomatic episodes of paroxysmal supraventricular tachycardia (PSVT) in adults. METHODS AND RESULTS: The study population was selected among 175 adult patients, affected by symptomatic PSVT. One hundred and six of them were considered eligible for the study. Each subject received one of the following treatments: verapamil, 5 mg intravenously (IV) in 5-10 min, followed by 1-5 microg/kg/min; adenosine, 6 mg IV, followed by 12 mg IV after 2-3 min; carotid sinus massage. Adenosine and verapamil were similarly effective in terminating PSVT (74.4% vs 81.8%, P=0.45). The efficacy of carotid sinus massage was significantly lower in comparison with the other two groups (32.4%, P=0.00032 vs adenosine and P=0.000044 vs verapamil group). At logistic regression, PSVT rate showed a positive association with the percentage of sinus rhythm restoration in the group who received adenosine (P=0.0004). The probability of success in resolving the tachycardia following treatment with adenosine was > 75% for heart rates over 166 beats per minute (bpm), but rapidly decreased at lower frequencies, reducing to 25% at 138 bpm. In the verapamil group, PSVT rate was negatively related to the percentage of sinus rhythm restoration (P=0.018). The probability of success in terminating PSVT following administration of verapamil was > 75% for heart rates lower than 186 bpm, but tended to decrease at faster rates, reducing to 25% at 241 bpm. No significant effects of heart rate were observed in the carotid sinus massage group (P=0.17). The probability curves obtained in the adenosine and verapamil group crossed at a point corresponding to 173 bpm, which may represent a cut-off value to predict which treatment could ensure higher rate of success. CONCLUSIONS: Heart rate predicts restoration of sinus rhythm in adult subjects with symptomatic episodes of PSVT treated with adenosine and verapamil. Adenosine is highly effective in PSVT characterised by fast rates, whereas the efficacy of verapamil is increased in patients with low-frequency PSVT.

Paroxysmal supraventricular tachycardia with persistent ventriculoatrial block.

We report the case of a 64-year-old patient with paroxysmal supraventricular tachycardia and persistent VA block. Induction and maintenance of tachycardia occurred without apparent activation of the atria. Diagnostic characteristics were most compatible with AV nodal reentrant tachycardia (AVNRT). Automatic junctional tachycardia and orthodromic nodoventricular or nodofascicular reentry tachycardia were considered in the differential diagnosis. Upper common pathway block during AVNRT may be explained by either intra-atrial conduction block or purely intranodal confined AVNRT. The arrhythmia was cured by a typical posteroseptal ablation approach guided by slow pathway potentials.

Cardiovascular responses to repetitive defibrillation during implantable cardioverter-defibrillator testing.

OBJECTIVE: To study the effects of electrical applications and subsequent postshock hypotension on myocardial performance and vascular tone during implantable cardioverter-defibrillator (ICD) placement. DESIGN: Prospective, blinded, observational investigation. SETTING: Single, university-affiliated institution. PARTICIPANTS: Twenty patients undergoing elective ICD placement and testing under general anesthesia. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Serial measurements were made of hemodynamic variables, left ventricular end-systolic (ESA) and end-diastolic (EDA) areas, fractional-area-of-contraction (FAC), time of hypoperfusion (when mean arterial pressure < or =50 mmHg postshock), and applied conversion energy. Multiple linear regression was performed to determine correlations among collected variables, and repeated measures analysis of variance was used to compare mean values. Minimal changes were detected in mean values of arterial, pulmonary, and central venous pressures; cardiac output; heart rate; and mixed venous saturation during repeated testing. Percentage changes in cardiac index (CI) rose and systemic vascular resistance index (SVRI) fell, however, as the number of shocks increased, reaching significance at the seventh and eighth shocks (v baseline; both p = 0.015). The percentage change in CI was linearly related to hypoperfusion time and accumulated energy (%deltaCI = 1.553 + [0.068 x sigma hypoperfusion time [sec]], r = 0.92, p < 0.001; %deltaCI = 0.326 + [0.125 x sigma Energy [J]], r = 0.94, p < 0.001). The percentage change in SVRI was inversely related to hypoperfusion time and accumulated energy (%deltaSVRI = 2.195 - [0.122 x sigma energy [J]], r = 0.79, p = 0.004; %deltaSVRI = 0.542 - [0.0634 - sigma hypoperfusion time [sec]], r = 0.73, p = 0.01). Echocardiographic EDA, ESA, and FAC were not significantly changed but showed substantial variability. CONCLUSION: Hemodynamic stability was generally well maintained during ICD placement and testing. Increases in CI were associated with concurrent reductions in systemic afterload, rather than enhanced FAC. Increasing postshock hypotension and applied energy were associated with decreases in CI and systemic afterload. Insignificant, but highly variable, changes were noted echocardiographically.

Electrophysiologic characteristics of ventricular extrastimulation-induced dissipation of functional bundle branch block associated with supraventricular tachycardia.

INTRODUCTION: Linking-related anterograde functional bundle branch block during supraventricular tachycardia (SVT) is due to repetitive concealed retrograde conduction of impulses from the contralateral bundle branch and can be eliminated by a critically timed premature ventricular beat (PVB). We assessed the electrophysiologic characteristics of PVB-induced dissipation of functional bundle branch block during SVT. METHODS AND RESULTS: During SVT with functional bundle branch block, PVB was delivered from the right ventricular apex, scanning the tachycardia cycle length (CL) with 10-msec decrements in the coupling interval in 14 patients (3 AV nodal reentrant tachycardia and 11 orthodromic AV reciprocating tachycardia). Dissipation was achieved in group 1: functional right bundle branch block (RBBB) in 4, functional left bundle branch block (LBBB) in 4, and both functional RBBB and LBBB in 1 with a dissipation zone occupying 4% to 13% (mean 8.5%) of the tachycardia CL. The outer limits were 22+/-16 msec and 68+/-14 msec < tachycardia CL; the inner limits were 56+/-18 msec and 90+/-24 msec < tachycardia CL for RBBB and LBBB, respectively (both P < 0.05). Dissipation could not be achieved in group 2 (4 RBBB and 1 LBBB) due to CL-dependent bundle branch block and/or local ventricular refractoriness. CONCLUSION: During SVT, functional bundle branch block due to "linking" often can be dissipated by timely PVB delivered from the right ventricular apex within a narrow zone of the tachycardia CL. Our findings suggest that the dissipation zone is affected by the pattern of functional bundle branch block relative to the site of PVB delivery.