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Conversion of atriopulmonary Fontan to extracardiac total cavopulmonary connection improves cardiopulmonary function
International Journal of Cardiology 113 (2006) 341 – 344 www.elsevier.com/locate/ijcard
Conversion of atriopulmonary Fontan to extracardiac total cavopulmonary connection improves cardiopulmonary function Alessandro Giardini a,*, Carlo Pace Napoleone b, Salvatore Specchia a, Andrea Donti a, Roberto Formigari a, Guido Oppido b, Gaetano Gargiulo b, Fernando M. Picchio a a
Pediatric Cardiology and Adult Congenital Unit, University of Bologna, Via Massarenti 9, 40138, Bologna, Italy b Pediatric Cardiac Surgery, University of Bologna, Italy Received 15 September 2005; received in revised form 9 November 2005; accepted 15 November 2005 Available online 5 January 2006
Abstract Background: Experimental studies showed that extracardiac total cavopulmonary connection provides superior hemodynamics than atriopulmonary Fontan. Methods: We prospectively assessed the impact of conversion of atriopulmonary Fontan to extracardiac total cavopulmonary connection on exercise capacity and cardiac function in 6 consecutive patients. Results: Six months after conversion to extracardiac total cavopulmonary connection, we observed an increase in peak oxygen uptake in all patients ( p = 0.01;+17%). This improvement was associated to an increase of peak O2 pulse ( p = 0.01;+16%), but no change in peak heart rate, arterial oxygen saturation at peak exercise, and pulmonary function. Ventricular ejection fraction did not change significantly after surgery. Conversion was associated with an improvement in heart failure symptoms as assessed by the New York Heart Association classification. Patients who had undergone additional anti-arrhythmia surgery for atrial fibrillation had no recurrence of arrhythmia at follow-up. Conclusion: Data indicate that conversion to extracardiac total cavopulmonary connection is associated with an improvement of cardiopulmonary function and heart failure symptoms. Improved exercise capacity is due to an increase in O2 pulse and may reflect an improved cardiac stroke volume after the operation. D 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Univentricular heart; Exercise testing; Cardiac surgery; Congenital heart disease
1. Introduction Fontan operation, first introduced in 1971 [1], has undergone several modifications aimed at diminishing or relieving right atrial enlargement and avoiding the presence of slow, turbulent systemic venous flow, which are the usual late consequences of the modified Fontan operation [2]. Right atrial enlargement and increased systemic venous pressure can cause atrial arrhythmias, compression of the right pulmonary veins, coronary sinus hypertension, forma-
* Corresponding author. Tel.: +39 051 6363435; fax: +39 051 6363461. E-mail address: [email protected] (A. Giardini). 0167-5273/$ - see front matter D 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2005.11.046
tion of atrial thrombi, and pulmonary embolism [3– 6]. Atriopulmonary Fontan connection may be associated in the long term with a low cardiac output state, a condition usually defined as failing Fontan circulation [7]. In vitro studies showed that surgical conversion to extracardiac total cavopulmonary connection improves the hemodynamics of the circuit reducing energy losses [8– 11], and is associated with increased response of refractory arrhythmias to medical therapy, overall improvement in quality of life and New York Heart Association (NYHA) class [7,12]. We hypothesized that conversion from atriopulmonary Fontan to extracardiac total cavopulmonary connection would be associated with an improvement in exercise tolerance and cardiac output response to exercise.
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A. Giardini et al. / International Journal of Cardiology 113 (2006) 341 – 344
2. Materials and methods
4. Echocardiography
Six consecutive patients underwent conversion from atriopulmonary Fontan to extracardiac total cavopulmonary connection at our institution. Median age at conversion was 19 years (14 to 23 years). The types of congenital heart disease leading to Fontan palliation are shown in Table 1. Indications for conversion to TCPC were advance NYHA class in 4 patients, debilitating atrial arrhythmias in 1 patient with ineffective medical therapy, and anatomic obstruction of the atriopulmonary junction in 1 patient. In a prospective fashion, all patients underwent transthoracic echocardiography and maximal cardiopulmonary exercise test, immediately before surgery and 6 months after. The local ethical committee approved the study, and informed consent was obtained from each patient.
Transthoracic echocardiography was performed using a multifrequency transducer interfaced with a Hewlett-Packard Sonos 5000 or 5500 echocardiograph (Hewlett-Packard, Andover, Massachusetts, USA). Ventricular ejection fraction was calculated from the apical four chamber view using manual planimetry and single plane Simpson’s rule. The degree of systemic atrio-ventricular valve regurgitation was semi-quantitatively graded as none, mild/moderate, and severe.
3. Surgical procedures All operations were performed on cardiopulmonary bypass under moderate hypothermia (28 -C). The conversion to total cavopulmonary connection was obtained with an external goretex vascular graft (W.L. Gore and Associates, Flagstaff, AZ) conduit of appropriate size in all cases. All operations were completed with a 5 mm fenestration between the conduit and the right atrium. Two patients underwent additional surgical therapy for chronic atrial fibrillation. The first patient was treated by MAZE III procedure [13], whereas the second patient received radiofrequency ablation using an endocardial monopolar probe, as described [14]. In both cases a surgical left atrial reduction plasty was performed, in order to increase the probability of success of rhythm control [15]. Additionally, the excision of the left atrial appendage was also carried out in order to reduce the embolic risks. All patients underwent implantation of permanent atrial and ventricular epicardial leads. A DDDR permanent pacemaker was implanted in the two patients who had undergone surgical therapy for chronic atrial fibrillation.
5. Cardiopulmonary exercise test Cardiopulmonary exercise test was performed on an electronically braked ergometer cycle (Ergoline, Germany). Oxygen uptake, carbon dioxide production, and minute ventilation were measured with a computerized breath-bybreath analyzer (V-MAX 29, Sensor-Medics). Patients performed a maximal exercise test using a 1-min incremental bicycle protocol. Initial workload was 10 W, with a work rate increment of 10 W/min. Criteria for test ending was considered patient exhaustion with a respiratory exchange ratio 1.09. A 12-lead electrocardiogram and transcutaneous oxygen saturation were also monitored throughout the study and cuff blood pressure was determined manually every 2 min. Peak oxygen uptake was calculated as the average of measurements made for 20 s before the end of exercise. None of the patients had additional coronary artery disease, known pulmonary disease or inability to exercise. Before exertion, a spirometric measurement was performed to assess forced vital capacity and forced expired volume in the first second. Standard equations were used to generate predicted values for baseline spirometric and peak exercise parameters [16].
6. Statistical analysis Data are expressed as median (range). Wilcoxon matched pairs test was used to compare preoperative vs. postoperative values. A p value < 0.05 was considered significant.
7. Results Table 1 Anatomic and clinical characteristics of the study cohort (n = 6) Patient
Diagnosis
Age at APC (years)
Age at TCPC (years)
AF
1 2 3 4 5 6
DILV TA DILV TA, PA DILV TA
3.5 4.5 5 4 5.5 3.2
19 14 23 21 19 18
+ 0 + 0 0 +
AF, atrial fibrillation; APC, atriopulmonary connection; DILV, double inlet left ventricle; PA, pulmonary atresia; TA, tricuspid atresia; TCPC, total cavopulmonary connection.
Median postoperative day at discharge was 19 (range 16 to 27). Medical therapy at discharge consisted of standard doses of diuretics and angiotensin converting enzyme inhibitors. All patients underwent oral anticoagulation for 6 months followed by aspirin administration. Two patients developed moderate arterial O2 desaturation shortly after surgery and they underwent transcatheter closure of the fenestration before discharge. No significant change in ventricular ejection fraction and arterial O2 saturation at rest was noted after conversion (Fig. 1). Before conversion, atrio-ventricular valve regurgitation was graded as mild/
A. Giardini et al. / International Journal of Cardiology 113 (2006) 341 – 344
343
Fig. 1. This figure shows the course of resting arterial O2 saturation (A) and ventricular ejection fraction (B).
moderate in 4 patients and severe in 2. After conversion atrio-ventricular valve regurgitation was graded as severe in 1 patient and mild/moderate in 5. Six months after conversion to total cavopulmonary connection, we observed an increase in peak oxygen uptake in all patients ( p = 0.01; median increase + 17%, range +6 to + 23%; Fig. 2). We also noted an increase in peak O2 pulse ( p = 0.01; median increase + 16%, range +9 to +40%; Table 2), whereas peak heart rate remained unchanged (median decrease 2%, range 11 to + 22%). Vital capacity, forced expired volume in the first second, and peak minute ventilation did not change after the operation, as did the respiratory quotient at peak exercise (median 1.14 vs. 1.13). Arterial O2 saturation at peak exercise was similar before and after conversion. Before surgery 4 patients were in New York Heart Association class III and 2 in class II. After surgery all patients were in New York Heart Association class II. After a median follow-up of 17 months (6 to 45) no patient has experienced atrial fibrillation.
8. Discussion Our study shows that conversion of atriopulmonary Fontan circuit to extracardiac total cavopulmonary connec-
tion is associated with a significant improvement of peak VO2. We could also confirm previous reports showing that conversion to TCPC is associated with improved NYHA functional class and ventricular ejection fraction [12,17]. Atriopulmonary connection may be associated with a low cardiac output state in the long term, a condition usually defined as failing Fontan circulation [7]. Increased venous pressure due to increased resistance to blood flow and increased energy losses in the atriopulmonary circuit trigger progressive right atrial dilation. Right atrial dilation causes further fluid energy losses and increases the energy required to move blood from the venae cavae to the pulmonary arteries [8], with subsequent increase in central venous pressure and decrease in cardiac output. Experimental studies have demonstrated that conversion to extracardiac total cavopulmonary connection provides superior hemodynamics than atriopulmonary connection and this advantage is particularly evident at physiologic flow rates that are representative of exercise [9]. We were able to demonstrate in vivo the beneficial effects of total cavopulmonary connection, leading to an increase of peak VO2. Our data indicate that the improvement in peak VO2 is largely due to an increase in peak O2 pulse, and this may indicate an increased stroke volume during exercise. A previous study showed that the systemic ventricle of Table 2 Cardiopulmonary test results before vs. 6 months after conversion to extracardiac total cavopulmonary connection Before Peak O2 pulse (ml O2/kg/beat) Peak HR (beats/min) Peak VE (l/min) VC (l/min) FEV1 (l/s) Arterial O2 saturation at peak exercise, %
Fig. 2. This figure shows the change in peak VO2 from before to 6 months after conversion to TCPC in each individual patient. VO2 indicates oxygen uptake.
After conversion
p value
4.9 (2.5 – 10.5)
5.7 (3.5 – 11.5)
0.01
136 (117 – 160)
134 (121 – 159)
0.88
55.4 3.5 2.8 91
(23.9 – 68.5) 56.5 (32.5 – 68.2) (2.2 – 4.7) 3.4 (2.3 – 4.6) (1.9 – 3.9) 2.9 (1.9 – 3.9) (87 – 94) 92 (88 – 93)
0.63 0.66 0.06 0.7
Values are expressed as median (range). FEV1, forced expired volume in the first second; HR, heart rate; VE, minute ventilation; VC, forced vital capacity; VCO2, carbon dioxide production.
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A. Giardini et al. / International Journal of Cardiology 113 (2006) 341 – 344
patients with an atriopulmonary Fontan has a reduced preload [2]. Reduced ventricular preload may be due to increased resistance to blood flow and increased energy losses caused by right atrial dilation [8,10]. Compression of the right pulmonary veins by a dilated right atrium has also been reported and can be associated with reduced ventricular preload [17]. Another factor that can cause power loss and reduced flow in the atriopulmonary circuit is the presence of a compliant section [18,19], like the dilated right atrium. During conversion to extracardiac total cavopulmonary connection, a prosthetic rigid tube is used to by-pass the right atrium. Furthermore, creation of a fenestration and placement of the coronary sinus into the systemic circulation can also increase ventricular preload. We hypothesize that after conversion to extracardiac total cavopulmonary connection, improvement in the hemodynamics of the circuit with the creation of a beneficial vortex [19,20], and increase in ventricular preload are associated with an increased cardiac output, especially under exercise conditions.
9. Study limitations We are aware that there is a recognized training effect that can lead to improvements in cardiopulmonary function when performing repeated exercise tests. However, due to the operation and the relatively long time between the 2 tests we think this effect is unlikely to be relevant. In addition, despite peak VO2 was improved in the present study, larger samples are necessary to conclude that conversion to TCPC improves cardiopulmonary function.
References [1] Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax 1971; 26:240 – 8. [2] Gewillig M. The Fontan circulation. Heart 2005;91:839 – 46. [3] Peters NS, Somerville J. Arrhythmias after the Fontan procedure. Br Heart J 1992;68:199 – 204. [4] Miura T, Hiramatsu T, Forbess JM, Mayer Jr JE. Effects of elevated coronary sinus pressure on coronary blood flow and left ventricular function: implications after the Fontan operation. Circulation 1995; 92:II298 – 303. [5] Kao JM, Alejos JC, Grant PW, Williams RG, Shannon KM, Laks H. Conversion of atriopulmonary to cavopulmonary anastomosis in
management of late arrhythmias and atrial thrombosis. Ann Thorac Surg 1994;58:1510 – 4. [6] Ilbawi MN, Idriss FS, Muster AJ, et al. Effects of elevated coronary sinus pressure on left ventricular function after the Fontan operation. An experimental and clinical correlation. J Thorac Cardiovasc Surg 1986;92:231 – 7. [7] Sheikh AM, Tang AT, Roman K, et al. The failing Fontan circulation: successful conversion of atriopulmonary connections. J Thorac Cardiovasc Surg 2004;128:60 – 6. [8] Lardo AC, Del Nido PJ, Webber SA, Friehs I, Cape EG. Hemodynamic effect of progressive right atrial dilatation in atriopulmonary connections. J Thorac Cardiovasc Surg 1997;114:2 – 8. [9] Lardo AC, Webber SA, Friehs I, Del Nido PJ, Cape EG. Fluid dynamic comparison of intra-atrial and extracardiac total cavopulmonary connections. J Thorac Cardiovasc Surg 1999;117(4):697 – 704. [10] Van Haesdonck JM, Martens L, Sizaire R, et al. Comparison by computerized numeric modeling of energy losses in different Fontan connections. Circulation 1995;92:II322. [11] de Leval MR, Kilner P, Gewillig M, Bull C. Total cavopulmonary connection: a logical alternative to atriopulmonary connection for complex Fontan operations. Experimental studies and early clinical experience. J Thorac Cardiovasc Surg 1988;96:682 – 95. [12] Mavroudis C, Backer CL, Deal BJ, Johnsrude C, Strasburger J. Total cavopulmonary conversion and maze procedure for patients with failure of the Fontan operation. J Thorac Cardiovasc Surg 2001;122: 863 – 871. [13] Cox JL, Schuessler RB, D’Agostino Jr HJ, et al. The surgical treatment of atrial fibrillation III: development of a definitive surgical procedure. J Thorac Cardiovasc Surg 1991;104:569 – 83. [14] Chiappini B, Martin-Suarez S, LoForte A, Di Bartolomeo R, Marinelli G. Surgery for atrial fibrillation using radiofrequency catheter ablation. J Thorac Cardiovas Surg 2003;126:1788 – 91. [15] Romano MA, Bach DS, Pagani FD, Prager RL, Deeb GM, Bolling SF. Atrial reduction plasty Cox maze procedure: extended indications for atrial fibrillation surgery. Ann Thorac Surg 2004;77:1282 – 7. [16] Wasserman K, Hansen JE, Sue DY. Principles of exercise testing and interpretation, 2nd edition . Philadelphia, PA’ Lea and Febiger, 1994. p. 66 – 133. [17] Agnoletti G, Borghi A, Vignati G, Crupi GC. Fontan conversion to total cavopulmonary connection and arrhythmia surgery: clinical and functional results. Heart 2003;89:193 – 8. [18]’ Ninam M, Myers JL. Conversion of the atriopulmonary Fontan connection to a total cavopulmonary connection. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 1998;1:23 – 30. [19] Masters JC, Ketner M, Bleiweis MS, Mill M, Yoganathan A, Lucas CL. The effect of incorporating vessel compliance in a computational model of blood flow in a total cavopulmonary connection (TCPC) with caval centerline offset. J Biomech Eng 2004;126(6):709 – 13. [20] Grigioni M, Amodeo A, Daniele C, D’Avenio G, Formigari R, Di Donato RM. Particle image velocimetry analysis of the flow field in the total cavopulmonary connection. Artif Organs 2000;24: 946 – 52.
Conversion of atriopulmonary Fontan to extracardiac total cavopulmonary connection improves cardiopulmonary function Alessandro Giardini a,*, Carlo Pace Napoleone b, Salvatore Specchia a, Andrea Donti a, Roberto Formigari a, Guido Oppido b, Gaetano Gargiulo b, Fernando M. Picchio a a
Pediatric Cardiology and Adult Congenital Unit, University of Bologna, Via Massarenti 9, 40138, Bologna, Italy b Pediatric Cardiac Surgery, University of Bologna, Italy Received 15 September 2005; received in revised form 9 November 2005; accepted 15 November 2005 Available online 5 January 2006
Abstract Background: Experimental studies showed that extracardiac total cavopulmonary connection provides superior hemodynamics than atriopulmonary Fontan. Methods: We prospectively assessed the impact of conversion of atriopulmonary Fontan to extracardiac total cavopulmonary connection on exercise capacity and cardiac function in 6 consecutive patients. Results: Six months after conversion to extracardiac total cavopulmonary connection, we observed an increase in peak oxygen uptake in all patients ( p = 0.01;+17%). This improvement was associated to an increase of peak O2 pulse ( p = 0.01;+16%), but no change in peak heart rate, arterial oxygen saturation at peak exercise, and pulmonary function. Ventricular ejection fraction did not change significantly after surgery. Conversion was associated with an improvement in heart failure symptoms as assessed by the New York Heart Association classification. Patients who had undergone additional anti-arrhythmia surgery for atrial fibrillation had no recurrence of arrhythmia at follow-up. Conclusion: Data indicate that conversion to extracardiac total cavopulmonary connection is associated with an improvement of cardiopulmonary function and heart failure symptoms. Improved exercise capacity is due to an increase in O2 pulse and may reflect an improved cardiac stroke volume after the operation. D 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Univentricular heart; Exercise testing; Cardiac surgery; Congenital heart disease
1. Introduction Fontan operation, first introduced in 1971 [1], has undergone several modifications aimed at diminishing or relieving right atrial enlargement and avoiding the presence of slow, turbulent systemic venous flow, which are the usual late consequences of the modified Fontan operation [2]. Right atrial enlargement and increased systemic venous pressure can cause atrial arrhythmias, compression of the right pulmonary veins, coronary sinus hypertension, forma-
* Corresponding author. Tel.: +39 051 6363435; fax: +39 051 6363461. E-mail address: [email protected] (A. Giardini). 0167-5273/$ - see front matter D 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2005.11.046
tion of atrial thrombi, and pulmonary embolism [3– 6]. Atriopulmonary Fontan connection may be associated in the long term with a low cardiac output state, a condition usually defined as failing Fontan circulation [7]. In vitro studies showed that surgical conversion to extracardiac total cavopulmonary connection improves the hemodynamics of the circuit reducing energy losses [8– 11], and is associated with increased response of refractory arrhythmias to medical therapy, overall improvement in quality of life and New York Heart Association (NYHA) class [7,12]. We hypothesized that conversion from atriopulmonary Fontan to extracardiac total cavopulmonary connection would be associated with an improvement in exercise tolerance and cardiac output response to exercise.
342
A. Giardini et al. / International Journal of Cardiology 113 (2006) 341 – 344
2. Materials and methods
4. Echocardiography
Six consecutive patients underwent conversion from atriopulmonary Fontan to extracardiac total cavopulmonary connection at our institution. Median age at conversion was 19 years (14 to 23 years). The types of congenital heart disease leading to Fontan palliation are shown in Table 1. Indications for conversion to TCPC were advance NYHA class in 4 patients, debilitating atrial arrhythmias in 1 patient with ineffective medical therapy, and anatomic obstruction of the atriopulmonary junction in 1 patient. In a prospective fashion, all patients underwent transthoracic echocardiography and maximal cardiopulmonary exercise test, immediately before surgery and 6 months after. The local ethical committee approved the study, and informed consent was obtained from each patient.
Transthoracic echocardiography was performed using a multifrequency transducer interfaced with a Hewlett-Packard Sonos 5000 or 5500 echocardiograph (Hewlett-Packard, Andover, Massachusetts, USA). Ventricular ejection fraction was calculated from the apical four chamber view using manual planimetry and single plane Simpson’s rule. The degree of systemic atrio-ventricular valve regurgitation was semi-quantitatively graded as none, mild/moderate, and severe.
3. Surgical procedures All operations were performed on cardiopulmonary bypass under moderate hypothermia (28 -C). The conversion to total cavopulmonary connection was obtained with an external goretex vascular graft (W.L. Gore and Associates, Flagstaff, AZ) conduit of appropriate size in all cases. All operations were completed with a 5 mm fenestration between the conduit and the right atrium. Two patients underwent additional surgical therapy for chronic atrial fibrillation. The first patient was treated by MAZE III procedure [13], whereas the second patient received radiofrequency ablation using an endocardial monopolar probe, as described [14]. In both cases a surgical left atrial reduction plasty was performed, in order to increase the probability of success of rhythm control [15]. Additionally, the excision of the left atrial appendage was also carried out in order to reduce the embolic risks. All patients underwent implantation of permanent atrial and ventricular epicardial leads. A DDDR permanent pacemaker was implanted in the two patients who had undergone surgical therapy for chronic atrial fibrillation.
5. Cardiopulmonary exercise test Cardiopulmonary exercise test was performed on an electronically braked ergometer cycle (Ergoline, Germany). Oxygen uptake, carbon dioxide production, and minute ventilation were measured with a computerized breath-bybreath analyzer (V-MAX 29, Sensor-Medics). Patients performed a maximal exercise test using a 1-min incremental bicycle protocol. Initial workload was 10 W, with a work rate increment of 10 W/min. Criteria for test ending was considered patient exhaustion with a respiratory exchange ratio 1.09. A 12-lead electrocardiogram and transcutaneous oxygen saturation were also monitored throughout the study and cuff blood pressure was determined manually every 2 min. Peak oxygen uptake was calculated as the average of measurements made for 20 s before the end of exercise. None of the patients had additional coronary artery disease, known pulmonary disease or inability to exercise. Before exertion, a spirometric measurement was performed to assess forced vital capacity and forced expired volume in the first second. Standard equations were used to generate predicted values for baseline spirometric and peak exercise parameters [16].
6. Statistical analysis Data are expressed as median (range). Wilcoxon matched pairs test was used to compare preoperative vs. postoperative values. A p value < 0.05 was considered significant.
7. Results Table 1 Anatomic and clinical characteristics of the study cohort (n = 6) Patient
Diagnosis
Age at APC (years)
Age at TCPC (years)
AF
1 2 3 4 5 6
DILV TA DILV TA, PA DILV TA
3.5 4.5 5 4 5.5 3.2
19 14 23 21 19 18
+ 0 + 0 0 +
AF, atrial fibrillation; APC, atriopulmonary connection; DILV, double inlet left ventricle; PA, pulmonary atresia; TA, tricuspid atresia; TCPC, total cavopulmonary connection.
Median postoperative day at discharge was 19 (range 16 to 27). Medical therapy at discharge consisted of standard doses of diuretics and angiotensin converting enzyme inhibitors. All patients underwent oral anticoagulation for 6 months followed by aspirin administration. Two patients developed moderate arterial O2 desaturation shortly after surgery and they underwent transcatheter closure of the fenestration before discharge. No significant change in ventricular ejection fraction and arterial O2 saturation at rest was noted after conversion (Fig. 1). Before conversion, atrio-ventricular valve regurgitation was graded as mild/
A. Giardini et al. / International Journal of Cardiology 113 (2006) 341 – 344
343
Fig. 1. This figure shows the course of resting arterial O2 saturation (A) and ventricular ejection fraction (B).
moderate in 4 patients and severe in 2. After conversion atrio-ventricular valve regurgitation was graded as severe in 1 patient and mild/moderate in 5. Six months after conversion to total cavopulmonary connection, we observed an increase in peak oxygen uptake in all patients ( p = 0.01; median increase + 17%, range +6 to + 23%; Fig. 2). We also noted an increase in peak O2 pulse ( p = 0.01; median increase + 16%, range +9 to +40%; Table 2), whereas peak heart rate remained unchanged (median decrease 2%, range 11 to + 22%). Vital capacity, forced expired volume in the first second, and peak minute ventilation did not change after the operation, as did the respiratory quotient at peak exercise (median 1.14 vs. 1.13). Arterial O2 saturation at peak exercise was similar before and after conversion. Before surgery 4 patients were in New York Heart Association class III and 2 in class II. After surgery all patients were in New York Heart Association class II. After a median follow-up of 17 months (6 to 45) no patient has experienced atrial fibrillation.
8. Discussion Our study shows that conversion of atriopulmonary Fontan circuit to extracardiac total cavopulmonary connec-
tion is associated with a significant improvement of peak VO2. We could also confirm previous reports showing that conversion to TCPC is associated with improved NYHA functional class and ventricular ejection fraction [12,17]. Atriopulmonary connection may be associated with a low cardiac output state in the long term, a condition usually defined as failing Fontan circulation [7]. Increased venous pressure due to increased resistance to blood flow and increased energy losses in the atriopulmonary circuit trigger progressive right atrial dilation. Right atrial dilation causes further fluid energy losses and increases the energy required to move blood from the venae cavae to the pulmonary arteries [8], with subsequent increase in central venous pressure and decrease in cardiac output. Experimental studies have demonstrated that conversion to extracardiac total cavopulmonary connection provides superior hemodynamics than atriopulmonary connection and this advantage is particularly evident at physiologic flow rates that are representative of exercise [9]. We were able to demonstrate in vivo the beneficial effects of total cavopulmonary connection, leading to an increase of peak VO2. Our data indicate that the improvement in peak VO2 is largely due to an increase in peak O2 pulse, and this may indicate an increased stroke volume during exercise. A previous study showed that the systemic ventricle of Table 2 Cardiopulmonary test results before vs. 6 months after conversion to extracardiac total cavopulmonary connection Before Peak O2 pulse (ml O2/kg/beat) Peak HR (beats/min) Peak VE (l/min) VC (l/min) FEV1 (l/s) Arterial O2 saturation at peak exercise, %
Fig. 2. This figure shows the change in peak VO2 from before to 6 months after conversion to TCPC in each individual patient. VO2 indicates oxygen uptake.
After conversion
p value
4.9 (2.5 – 10.5)
5.7 (3.5 – 11.5)
0.01
136 (117 – 160)
134 (121 – 159)
0.88
55.4 3.5 2.8 91
(23.9 – 68.5) 56.5 (32.5 – 68.2) (2.2 – 4.7) 3.4 (2.3 – 4.6) (1.9 – 3.9) 2.9 (1.9 – 3.9) (87 – 94) 92 (88 – 93)
0.63 0.66 0.06 0.7
Values are expressed as median (range). FEV1, forced expired volume in the first second; HR, heart rate; VE, minute ventilation; VC, forced vital capacity; VCO2, carbon dioxide production.
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A. Giardini et al. / International Journal of Cardiology 113 (2006) 341 – 344
patients with an atriopulmonary Fontan has a reduced preload [2]. Reduced ventricular preload may be due to increased resistance to blood flow and increased energy losses caused by right atrial dilation [8,10]. Compression of the right pulmonary veins by a dilated right atrium has also been reported and can be associated with reduced ventricular preload [17]. Another factor that can cause power loss and reduced flow in the atriopulmonary circuit is the presence of a compliant section [18,19], like the dilated right atrium. During conversion to extracardiac total cavopulmonary connection, a prosthetic rigid tube is used to by-pass the right atrium. Furthermore, creation of a fenestration and placement of the coronary sinus into the systemic circulation can also increase ventricular preload. We hypothesize that after conversion to extracardiac total cavopulmonary connection, improvement in the hemodynamics of the circuit with the creation of a beneficial vortex [19,20], and increase in ventricular preload are associated with an increased cardiac output, especially under exercise conditions.
9. Study limitations We are aware that there is a recognized training effect that can lead to improvements in cardiopulmonary function when performing repeated exercise tests. However, due to the operation and the relatively long time between the 2 tests we think this effect is unlikely to be relevant. In addition, despite peak VO2 was improved in the present study, larger samples are necessary to conclude that conversion to TCPC improves cardiopulmonary function.
References [1] Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax 1971; 26:240 – 8. [2] Gewillig M. The Fontan circulation. Heart 2005;91:839 – 46. [3] Peters NS, Somerville J. Arrhythmias after the Fontan procedure. Br Heart J 1992;68:199 – 204. [4] Miura T, Hiramatsu T, Forbess JM, Mayer Jr JE. Effects of elevated coronary sinus pressure on coronary blood flow and left ventricular function: implications after the Fontan operation. Circulation 1995; 92:II298 – 303. [5] Kao JM, Alejos JC, Grant PW, Williams RG, Shannon KM, Laks H. Conversion of atriopulmonary to cavopulmonary anastomosis in
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