Biomedical subjects

S Adam Strickberger

Publications and source records attributed to S Adam Strickberger.

44 records · Page 3Linked to original sources

PubMed2002

Differentiation of atrial and pulmonary vein potentials recorded circumferentially within pulmonary veins.

INTRODUCTION: Accurate discrimination of atrial and pulmonary vein potentials recorded circumferentially within the pulmonary veins is important when performing segmental isolation of the pulmonary veins in patients with atrial fibrillation. METHODS AND RESULTS: Twenty patients with paroxysmal atrial fibrillation underwent pulmonary vein mapping with a decapolar Lasso catheter during sinus rhythm and during pacing in the distal coronary sinus and left atrial appendage. Bipolar and unipolar electrograms were recorded within the left superior, right superior, and left inferior pulmonary veins. The atrial potentials were larger in the left pulmonary veins than in the right superior pulmonary vein, whereas the pulmonary vein potentials in the superior pulmonary veins were larger than in the left inferior pulmonary vein. The atrial and pulmonary vein potentials usually were readily distinguished during sinus rhythm in the right superior pulmonary vein. Characteristic distribution and morphologies of the atrial potentials as well as the response to distal coronary sinus and left atrial appendage pacing were useful for differentiating the atrial and pulmonary vein potentials in the left pulmonary veins. CONCLUSION: Atrial and pulmonary vein potentials recorded circumferentially within the pulmonary veins have characteristic features that are useful in distinguishing them from each other. In the left pulmonary veins, discrimination of the atrial and pulmonary vein potentials is aided by coronary sinus or left atrial appendage pacing.

Analysis of Variance↗

PubMed2002

Effects of verapamil and ibutilide on atrial fibrillation and postfibrillation atrial refractoriness.

INTRODUCTION: Early recurrence of atrial fibrillation (AF) after cardioversion may be related to shortening of the atrial effective refractory period (ERP). This study compared the effects of verapamil and ibutilide on AF cycle length (AFCL), atrial ERP, and susceptibility to recurrent AF. METHODS AND RESULTS: In 33 adults, the atrial ERP was measured at basic drive CLs of 350 and 500 msec before and after a brief episode of pacing-induced AF. During AF, verapamil, ibutilide, or saline was infused in 11 patients each. Shortening of the post-AF atrial ERP was attenuated by verapamil and prevented by ibutilide. AFCL shortened by 32+/-21 msec in the verapamil group (P < 0.01), prolonged by 44+/-14 msec in the ibutilide group (P < 0.001), and did not change in the control group. AF converted to sinus rhythm within 10 minutes less often after verapamil (0%) than after ibutilide (82%) or than in the control group (73%). Post-AF, AF lasting > 10 minutes was induced more often in the verapamil group than in the ibutilide group (26% vs 0%; P = 0.01). Another 10 patients received verapamil or ibutilide in the absence of AF. Atrial ERP was unchanged after verapamil and prolonged after ibutilide. CONCLUSION: Verapamil shortens AFCL and impedes the conversion of induced AF, whereas ibutilide prolongs AFCL and does not impede the early conversion of induced AF. Ibutilide is more effective than verapamil in preventing pos

Adult↗

PubMed2002

Prevalence of a shared isthmus in postinfarction patients with pleiomorphic, hemodynamically tolerated ventricular tachycardias.

INTRODUCTION: Multiple forms of ventricular tachycardia (VT) after myocardial infarction may result from multiple reentrant circuits that share an isthmus or from separate reentrant circuits. The prevalence of a shared isthmus in patients with multiple hemodynamically tolerated VTs has not been determined. METHODS AND RESULTS: Criteria for a shared isthmus consisted of (1) concealed entrainment of >1 VT at a single pacing site; (2) concealed entrainment during VT and a perfect pace map of another VT at the same pacing site; or (3) concealed entrainment of VT of a given morphology that had at least two cycle lengths that varied by at least 100 msec. In a series of 19 patients (16 men and 3 women; age 65+/-14 years, ejection fraction 0.25+/-0.09) with 54 VTs (mean cycle length 494+/-98 msec), there was evidence of a shared isthmus in 23 VTs (43%) at 11 sites in 9 patients. Concealed entrainment of two different VTs was observed at 4 of 11 sites. At 5 of 11 sites there was concealed entrainment of one VT and a perfect pace map of another VT. At the remaining 2 of 11 sites, there was concealed entrainment of a VT that had two different cycle lengths. Nineteen of the 23 VTs were ablated successfully with radiofrequency energy applications at 11 sites. CONCLUSION: In postinfarction patients with pleiomorphic, hemodynamically stable VT, a shared isthmus may be present in approximately 40% of VTs.

Aged↗

PubMed2002

Mechanistic significance of intermittent pulmonary vein tachycardia in patients with atrial fibrillation.

INTRODUCTION: The significance of intermittent tachycardia within a pulmonary vein (PV) during an episode of atrial fibrillation (AF) is unclear. The aim of this study was to determine the role that intermittent PV tachycardias play in AF. METHODS AND RESULTS: In 56 patients with AF, segmental ostial ablation guided by PV potentials was performed to isolate the PVs. The characteristics of intermittent PV tachycardias and the inducibility of AF before and after PV isolation were analyzed prospectively. During AF, a PV tachycardia (mean cycle length 130 +/- 30 msec) with exit block to the left atrium was present in 93% of left superior, 80% of left inferior, 73% of right superior, and 7% of right inferior PVs. The site of shortest cycle length during AF alternated between the PVs and left atrium 1 to 13 times per minute. Complete isolation was achieved in 168 (94%) of 178 targeted PVs. In 99% of PVs, tachycardia resolved upon isolation. AF was persistent before and after PV isolation in 100% and 27% of patients, respectively (P < 0.001). CONCLUSION: Intermittent bursts of tachycardia are observed within multiple PVs during persistent AF in a majority of patients. After PV isolation, PV tachycardias almost always resolve, and AF is less likely to be inducible or persistent. These observations suggest a dynamic interplay between the atria and PVs, with intermittent bursts of PV tachycardia being dependent on left atrial input and with the probability of persistent AF diminishing when PV tachycardias are eliminated by PV isolation.

Analysis of Variance↗

PubMed2002

Randomized comparison of anatomic and electrogram mapping approaches to ablation of typical atrial flutter.

INTRODUCTION: The cavotricuspid isthmus can be ablated using an anatomic approach or an electrogram mapping approach in which sites at which there is a gap in the line of block are targeted. The aim of this study was to compare the anatomic and electrogram mapping approaches for creating a line of block in the cavotricuspid isthmus after an initial, unsuccessful anatomically directed ablation line. METHODS AND RESULTS: The subjects of this study were 63 patients with isthmus-dependent atrial flutter in whom a single series of contiguous applications of radiofrequency energy guided by fluoroscopy in the cavotricuspid isthmus did not result in complete block. The patients were randomly assigned to additional ablation on an anatomic basis (n = 31) or guided by single potentials or narrowly split double potentials during coronary sinus pacing (n = 32). After every 15 applications of radiofrequency energy, the alternate approach was used until complete block was achieved. Before cross-over, complete block was achieved in 6 patients (19%) with the anatomic approach compared with 19 patients (59%) with the electrogram mapping approach (P < 0.005). The electrogram mapping approach also was more effective than the anatomic approach in achieving complete isthmus block after the first cross-over (72% vs 23%, P < 0.005) and after the second cross-over (80% vs 42%, P < 0.05). CONCLUSION: When there is incomplete block after an initial series of applications of radiofrequency energy in the cavotricuspid isthmus, complete block is achieved more efficiently with an electrogram mapping approach than with an anatomic approach.

Atrial Flutter↗

PubMed2002

Randomized comparison of bipolar versus unipolar plus bipolar recordings during segmental ostial ablation of pulmonary veins.

INTRODUCTION: Segmental ostial ablation to isolate pulmonary veins is guided by pulmonary vein potentials. The aim of this prospective randomized study was to compare the utility of unipolar plus bipolar electrograms versus only bipolar electrograms as a guide for segmental ablation to isolate the pulmonary veins in patients with atrial fibrillation. METHODS AND RESULTS: Isolation of the left superior, right superior, and left inferior pulmonary veins was attempted in 44 patients (35 men and 9 women; mean age 54 +/- 10 years) with paroxysmal atrial fibrillation. A decapolar Lasso catheter was positioned in the pulmonary veins, near the ostium, and a conventional ablation catheter was used for segmental ablation aimed at elimination of all pulmonary vein potentials. One hundred fourteen pulmonary veins were randomly assigned for ostial ablation guided by either bipolar or unipolar plus bipolar recordings. Electrical isolation was achieved in 51 (96%) of 53 pulmonary veins randomized to the bipolar approach, and 57 (93%) of 61 pulmonary veins randomized to the unipolar plus bipolar approach (P = 0.7). In the unipolar plus bipolar group, the total duration of radiofrequency energy needed to achieve isolation, 5.5 +/- 2.8 minutes/vein, was significant shorter than in the bipolar group, 7.6 +/- 4.1 minutes/vein (P < 0.01). Mean procedure and fluoroscopy durations per vein were 19% to 28% shorter in the unipolar plus bipolar group. CONCLUSION: Segmental ostial ablation to isolate the pulmonary veins can be achieved more efficiently and with less radiofrequency energy when guided by both unipolar and bipolar recordings than by bipolar recordings alone.

Adult↗

PubMed2002

Effects of diltiazem and esmolol on cycle length and spontaneous conversion of atrial fibrillation.

BACKGROUND: Calcium channel blocking agents have been shown to prolong the duration of atrial fibrillation. This study compared the effects of intravenous diltiazem and esmolol on the cycle length and conversion rate of pacing-induced atrial fibrillation. METHODS AND RESULTS: In 41 adults without structural heart disease, atrial fibrillation was induced by rapid atrial pacing. After 3 minutes, either diltiazem (n = 13), esmolol (n = 15), or saline (n = 13) was infused. In the diltiazem group, the atrial fibrillation cycle length shortened by a mean of 43 milliseconds and became significantly shorter than in the control group, while the atrial fibrillation cycle length in the esmolol group did not change. Spontaneous termination of atrial fibrillation occurred significantly less often in the diltiazem group (23%) than in the esmolol (67%, P < 0.05) or placebo groups (77%, P = 0.01). CONCLUSIONS: Intravenous diltiazem shortens the atrial fibrillation cycle length and lowers the probability of spontaneous conversion of recent-onset atrial fibrillation to sinus rhythm. These results suggest that the use of diltiazem for acute rate control may unwittingly prolong the duration of recent-onset atrial fibrillation.

Adult↗

PubMed2002

Comparison of verapamil and ibutilide for the suppression of immediate recurrences of atrial fibrillation after transthoracic cardioversion.

BACKGROUND: Verapamil and ibutilide blunt the atrial fibrillation-induced shortening of atrial refractoriness that may predispose to an immediate recurrence of atrial fibrillation after cardioversion. This study compared the efficacy of verapamil and ibutilide in preventing an immediate recurrence of atrial fibrillation. METHODS AND RESULTS: Transthoracic cardioversion was performed in 223 patients with atrial fibrillation. Atrial fibrillation recurred within 10 minutes after cardioversion on two occasions in 21 patients (9.4%). Twenty of these patients were randomly assigned to receive an infusion of either 0.15 mg/kg of verapamil at a rate of 2 mg/min (11 patients), or 1 mg of ibutilide over 10 minutes (9 patients). Eight patients (73%) had another episode of immediate recurrence of atrial fibrillation after verapamil, compared to two patients (22%) after ibutilide (P<0.05). Including the results after crossover, immediate recurrence of atrial fibrillation occurred in 8 of 12 patients (67%) who received verapamil, compared to 3 of 16 patients (19%) who received ibutilide (P=0.02). Verapamil and/or ibutilide successfully prevented immediate recurrence of atrial fibrillation in 17 of 20 patients (85%). After 700 days of follow-up, there was no significant difference in the recurrence rate of atrial fibrillation between the patients in whom immediate recurrence of atrial fibrillation was prevented by verapamil and/or ibutilide and the patients who were successfully converted to sinus rhythm and did not have immediate recurrence of atrial fibrillation. CONCLUSIONS: Ibutilide is more effective than verapamil in preventing immediate recurrence of atrial fibrillation. Suppression of immediate recurrence of atrial fibrillation by ibutilide and/or verapamil may allow for long-term maintenance of sinus rhythm postcardioversion as often as in patients who do not experience immediate recurrence of atrial fibrillation.

Aged↗