Mark A. Milton

Discrepancies Between Catheter Tip and Tissue Temperature in Cooled-Tip Ablation Relevance to Guiding Left Atrial Ablation

Background—It is not known whether catheter tip temperatures with a cooled-tip ablation can be reliably extrapolated to estimate actual tissue temperatures. The relationship between catheter tip temperatures, tissue temperatures, power, and microbubble formation is not known. Methods and Results—Nine dogs underwent 111 radiofrequency energy deliveries at the pulmonary vein ostia with a cooled-tip catheter. Catheter tip and tissue temperatures were markedly discrepant. Catheter tip temperature plateaus at 36°C to 39°C with increasing power, whereas tissue temperature increases to a mean of 75±3°C at 45 W (maximum temperature >100°C). Seventy-two energy deliveries were performed, titrating power to microbubble formation guided by intracardiac echocardiography. Type I and II microbubble formation occurred in 45 (63%) and 19 (26%) ablations, respectively. Type I microbubble emergence occurred at lower powers (21±8 versus 26±4 W; P=0.05), catheter tip temperatures (38±5°C versus 48±10°C; P=0.02), and tissue temperatures (65±19°C versus 81±9°C; P<0.001) than type II microbubble formation. Maximum impedance decreases during ablation before microbubble formation were less with type I microbubble (20±9 versus 37±11 &OHgr;; P<0.001) compared with type II microbubbles. One quarter of type I microbubbles abruptly transitioned to type II microbubbles with significant changes in power or catheter tip temperature. No microbubbles were seen in 19 ablations (26%) despite powers up to 26±9 W and tissue temperatures up to 81±17°C. Conclusions—Catheter tip and tissue temperatures are markedly discrepant during cooled-tip ablation. Type I and II microbubble formation occurs at overlapping power and catheter tip and tissue temperature ranges. Neither the absence of microbubbles nor the presence of type I microbubble formation ensures against excessive tissue heating. The appearance of microbubbles may indicate possible tissue overheating and signal a need to decrease energy.

Analysis of Catheter-Tip (8-mm) and Actual Tissue Temperatures Achieved During Radiofrequency Ablation at the Orifice of the Pulmonary Vein

Background—Many ablative approaches in or near the orifice of the pulmonary vein (PV) have demonstrated success in eliminating atrial fibrillation. Despite current practice, there are no data regarding the in vivo efficacy and safety of an 8-mm catheter tip for ablation at the PV orifice. Methods and Results—Ten mongrel dogs were studied. Thermocouples were implanted in the atrial muscle of the PV orifice. Intracardiac echocardiography monitored catheter position, tip/tissue orientation, and microbubble formation. Ninety-four ablations were performed for 120 seconds. A temperature discrepancy >10°C between the catheter tip and tissue occurred during 47 (50%) of the ablations. Despite termination of energy delivery, the average tissue temperature remained within 1°C of the achieved steady state for 9 seconds. A temperature discrepancy >10°C was more common in the right superior PV, with oblique catheter positioning, when tissue temperatures were >60°C or 80°C, and with type 1 or type 2 microbubble formation. However, microbubbles were not present in 7 (13%, type 1) and 10 (40%, type 2) ablations with tissue temperatures >80°C. The maximum tissue temperature achieved with non–full-thickness lesions was 47.3±7.4°C vs 75.9±11.7°C (P<0.0001) for full-thickness lesions. Conclusions—Marked discrepancies between catheter-tip and tissue temperatures occurred with higher temperatures, prolonged ablation times, and unfavorable catheter thermistor–tissue contact. Also, these data suggest a conservative approach to atrial ablation, because full-thickness lesions were obtained when tissue temperatures reached 50°C to 60°C and the tissue retained high heat levels despite termination of radiofrequency energy. Finally, microbubbles are inconsistent markers of tissue overheating.

Utility of intracardiac ultrasound imaging to guide pulmonary vein ablation using laser balloon catheter

FUNDAMENTO: O isolamento das veias pulmonares (IVP) tem sido usado como endpoint para a ablacao da fibrilacao atrial (FA) com cateter balao. OBJETIVO: Determinar a utilidade do ultrassom intracardiaco (USIC) para guiar o IVP, usando cateter balao a laser. METODOS: 59 VP foram ablacionadas em 27 caes. Imagens de Doppler foram usadas para identificar os vazamentos do fluxo sanguineo entre a VP e o balao. Apos cada liberacao de energia, o cateter de mapeamento circular foi reposicionado para verificar se o isolamento tinha sido obtido. A posicao de vazamento foi entao correlacionada com a posicao do gap no estudo patologico. A analise de regressao logistica multivariada foi realizada. RESULTADOS: Cinquenta e nove VP foram submetidas a ablacao. O tempo medio de energia liberada foi de 279±177 seg., o diâmetro medio do balao era de 23±3 mm, e o comprimento medio do balao era 25±4 mm. O isolamento completo foi obtido em 38/59 (64%), e foi significantemente mais comum sem vazamento: [30/38 (79%) versus 8/23 (35%), p<0,001]. Isso foi independente do tempo de aplicacao (302±223 seg. vs. 266±148 sec., p=ns), potencia (3,5 W/cm, 4,5 W/cm, e 5,5 W/cm), diâmetro do balao (24± 3 mm vs. 22± 3 mm, p= ns) e comprimento (27±4 mm vs. 24±4 mm, p=ns). O valor preditivo positivo para previsao de isolamento completo foi de 65% e o valor preditivo negativo foi 83%. CONCLUSAO: Um vazamento identificavel entre a VP e o dispositivo de ablacao por cateter-balao observado no USIC e preditor de menor taxa de isolamento de VP mais baixas. O USIC pode ser util para detectar vazamentos a fim de evitar o uso ineficaz de aplicacao energia durante a ablacao circunferencial da VP. Isto tambem pode ser util quando outras energias sao utilizadas.BACKGROUND Pulmonary vein isolation (PVI) with balloon catheter has been used as the endpoint for AF ablation. OBJECTIVE To determine the usefulness of intracardiac ultrasound (ICUS) to guide PVI using laser balloon catheter. METHODS 59 PVs were ablated in 27 dogs. Doppler imaging was used to identify blood flow leaks between PV and balloon. After each energy delivery, the circular mapping catheter was repositioned to check if isolation had been achieved. The leak position was then correlated with the gap position at the pathological study. Multivariate logistic regression analysis was undertaken. RESULTS 59 PV were ablated. Mean burn time was 279+/-177 sec, mean balloon diameter was 23+/-3 mm, and mean balloon length was 25+/-4 mm. Complete isolation was achieved in 38/59 (64%) cases, and it was significantly more common when there was no leak: [30/38 (79%) versus 8/23 (35%), p<0.001]. This occurred regardless of time of laser application (302+/-223 sec. vs. 266+/-148 sec., p=ns), laser power (3.5 W/cm, 4.5 W/cm, and 5.5 W/cm), balloon diameter (24+/- 3 mm vs. 22+/- 3 mm, p=ns) and length (27+/-4 mm vs. 24+/-4mm, p=ns). The positive predictive value for predicting incomplete isolation was 65% and the negative predictive value was 83%. CONCLUSION An identifiable leak between PV and the LBA device seen at the ICUS is predictive of lower PV isolation rates. ICUS may be useful for leak detection to avoid ineffective energy application during circumferential PV ablation. This could also be helpful when other types of energy are used.

Utilidade do Ultrassom intracardíaco no isolamento de veias pulmonares usando cateter-balão a laser

FUNDAMENTO: O isolamento das veias pulmonares (IVP) tem sido usado como endpoint para a ablacao da fibrilacao atrial (FA) com cateter balao. OBJETIVO: Determinar a utilidade do ultrassom intracardiaco (USIC) para guiar o IVP, usando cateter balao a laser. METODOS: 59 VP foram ablacionadas em 27 caes. Imagens de Doppler foram usadas para identificar os vazamentos do fluxo sanguineo entre a VP e o balao. Apos cada liberacao de energia, o cateter de mapeamento circular foi reposicionado para verificar se o isolamento tinha sido obtido. A posicao de vazamento foi entao correlacionada com a posicao do gap no estudo patologico. A analise de regressao logistica multivariada foi realizada. RESULTADOS: Cinquenta e nove VP foram submetidas a ablacao. O tempo medio de energia liberada foi de 279±177 seg., o diâmetro medio do balao era de 23±3 mm, e o comprimento medio do balao era 25±4 mm. O isolamento completo foi obtido em 38/59 (64%), e foi significantemente mais comum sem vazamento: [30/38 (79%) versus 8/23 (35%), p<0,001]. Isso foi independente do tempo de aplicacao (302±223 seg. vs. 266±148 sec., p=ns), potencia (3,5 W/cm, 4,5 W/cm, e 5,5 W/cm), diâmetro do balao (24± 3 mm vs. 22± 3 mm, p= ns) e comprimento (27±4 mm vs. 24±4 mm, p=ns). O valor preditivo positivo para previsao de isolamento completo foi de 65% e o valor preditivo negativo foi 83%. CONCLUSAO: Um vazamento identificavel entre a VP e o dispositivo de ablacao por cateter-balao observado no USIC e preditor de menor taxa de isolamento de VP mais baixas. O USIC pode ser util para detectar vazamentos a fim de evitar o uso ineficaz de aplicacao energia durante a ablacao circunferencial da VP. Isto tambem pode ser util quando outras energias sao utilizadas.BACKGROUND Pulmonary vein isolation (PVI) with balloon catheter has been used as the endpoint for AF ablation. OBJECTIVE To determine the usefulness of intracardiac ultrasound (ICUS) to guide PVI using laser balloon catheter. METHODS 59 PVs were ablated in 27 dogs. Doppler imaging was used to identify blood flow leaks between PV and balloon. After each energy delivery, the circular mapping catheter was repositioned to check if isolation had been achieved. The leak position was then correlated with the gap position at the pathological study. Multivariate logistic regression analysis was undertaken. RESULTS 59 PV were ablated. Mean burn time was 279+/-177 sec, mean balloon diameter was 23+/-3 mm, and mean balloon length was 25+/-4 mm. Complete isolation was achieved in 38/59 (64%) cases, and it was significantly more common when there was no leak: [30/38 (79%) versus 8/23 (35%), p<0.001]. This occurred regardless of time of laser application (302+/-223 sec. vs. 266+/-148 sec., p=ns), laser power (3.5 W/cm, 4.5 W/cm, and 5.5 W/cm), balloon diameter (24+/- 3 mm vs. 22+/- 3 mm, p=ns) and length (27+/-4 mm vs. 24+/-4mm, p=ns). The positive predictive value for predicting incomplete isolation was 65% and the negative predictive value was 83%. CONCLUSION An identifiable leak between PV and the LBA device seen at the ICUS is predictive of lower PV isolation rates. ICUS may be useful for leak detection to avoid ineffective energy application during circumferential PV ablation. This could also be helpful when other types of energy are used.

Utilidad del ultrasonido intracardíaco en el aislamiento de venas pulmonares usando catéter-balón láser

FUNDAMENTO: O isolamento das veias pulmonares (IVP) tem sido usado como endpoint para a ablacao da fibrilacao atrial (FA) com cateter balao. OBJETIVO: Determinar a utilidade do ultrassom intracardiaco (USIC) para guiar o IVP, usando cateter balao a laser. METODOS: 59 VP foram ablacionadas em 27 caes. Imagens de Doppler foram usadas para identificar os vazamentos do fluxo sanguineo entre a VP e o balao. Apos cada liberacao de energia, o cateter de mapeamento circular foi reposicionado para verificar se o isolamento tinha sido obtido. A posicao de vazamento foi entao correlacionada com a posicao do gap no estudo patologico. A analise de regressao logistica multivariada foi realizada. RESULTADOS: Cinquenta e nove VP foram submetidas a ablacao. O tempo medio de energia liberada foi de 279±177 seg., o diâmetro medio do balao era de 23±3 mm, e o comprimento medio do balao era 25±4 mm. O isolamento completo foi obtido em 38/59 (64%), e foi significantemente mais comum sem vazamento: [30/38 (79%) versus 8/23 (35%), p<0,001]. Isso foi independente do tempo de aplicacao (302±223 seg. vs. 266±148 sec., p=ns), potencia (3,5 W/cm, 4,5 W/cm, e 5,5 W/cm), diâmetro do balao (24± 3 mm vs. 22± 3 mm, p= ns) e comprimento (27±4 mm vs. 24±4 mm, p=ns). O valor preditivo positivo para previsao de isolamento completo foi de 65% e o valor preditivo negativo foi 83%. CONCLUSAO: Um vazamento identificavel entre a VP e o dispositivo de ablacao por cateter-balao observado no USIC e preditor de menor taxa de isolamento de VP mais baixas. O USIC pode ser util para detectar vazamentos a fim de evitar o uso ineficaz de aplicacao energia durante a ablacao circunferencial da VP. Isto tambem pode ser util quando outras energias sao utilizadas.BACKGROUND Pulmonary vein isolation (PVI) with balloon catheter has been used as the endpoint for AF ablation. OBJECTIVE To determine the usefulness of intracardiac ultrasound (ICUS) to guide PVI using laser balloon catheter. METHODS 59 PVs were ablated in 27 dogs. Doppler imaging was used to identify blood flow leaks between PV and balloon. After each energy delivery, the circular mapping catheter was repositioned to check if isolation had been achieved. The leak position was then correlated with the gap position at the pathological study. Multivariate logistic regression analysis was undertaken. RESULTS 59 PV were ablated. Mean burn time was 279+/-177 sec, mean balloon diameter was 23+/-3 mm, and mean balloon length was 25+/-4 mm. Complete isolation was achieved in 38/59 (64%) cases, and it was significantly more common when there was no leak: [30/38 (79%) versus 8/23 (35%), p<0.001]. This occurred regardless of time of laser application (302+/-223 sec. vs. 266+/-148 sec., p=ns), laser power (3.5 W/cm, 4.5 W/cm, and 5.5 W/cm), balloon diameter (24+/- 3 mm vs. 22+/- 3 mm, p=ns) and length (27+/-4 mm vs. 24+/-4mm, p=ns). The positive predictive value for predicting incomplete isolation was 65% and the negative predictive value was 83%. CONCLUSION An identifiable leak between PV and the LBA device seen at the ICUS is predictive of lower PV isolation rates. ICUS may be useful for leak detection to avoid ineffective energy application during circumferential PV ablation. This could also be helpful when other types of energy are used.