- Email: [email protected]
Extrapleural Intrathoracic Pacemaker for Congenital Heart Block
334
CORRESPONDENCE
grafting (CABG). We read this article with extreme interest and would like to add some comments on the topic. The prognosis of patients with PAD is related to the presence and extent of underlying coronary arterial disease (CAD). Because PAD is associated with more severe and extensive CAD, it is well known that PAD is an independent predictor of poor long-term survival among patients undergoing CABG [1, 2]. However, the topic of short–term mortality after CABG is debatable. Although numerous studies have demonstrated adverse short-term outcomes among patients with PAD who undergo CABG [2], the present study reports that PAD does not affect early outcomes in patients who undergo CABGs. We believe that one of the mechanisms of this interesting finding may be remote ischemic preconditioning (RIPC). Cardioprotection was first conceived in the late 1980s and has evolved to include endogenous cardioprotective ischemic preconditioning, which protects the heart from an episode of acute lethal ischemia–reperfusion injury by applying brief nonlethal episodes of ischemia. Later it was shown that brief, controlled episodes of intermittent ischemia of the arm or leg may confer powerful protection against prolonged ischemia in a distant organ; thus, the concept of RIPC is now popular [3]. In 1997, Birnbaum and colleagues [4] published the first study suggesting that transient limb ischemia could remotely precondition the ischemic heart. Subsequently, RIPC induced by transient limb ischemia was shown to reduce ischemic myocardial damage during CABG [5]. In the present study, RIPC triggered by intermittent claudication secondary to PAD may be responsible for preventing early mortality after CABG. First described almost 15 years ago, this concept has been slow to translate into clinical practice. We believe that clinical applicability should be further studied in large, multi-center randomized trials.
Ann Thorac Surg 2011;91:330 – 6
Extrapleural Intrathoracic Pacemaker for Congenital Heart Block To the Editor: We had previously reported our experience with extrapleural intrathoracic pacemaker implantation in children and low birthweight infants [1]. This approach has the advantages of a single incision for lead and generator placement, security of the generator under the thoracic cage, and less chance of lead fracture. Another recently suggested option in a 1.3-kg child has been to place the generator between the parietal pericardium and diaphragm muscle [2].
Ozcan Ozeke, MD Mutlu Gungor, MD Can Ozer, MD Department of Cardiology Bayindir Hospital Kardiyoloji Klinigi, Sögütözü Ankara, 06520 Turkey e-mail: [email protected]
Fig 1. The previously placed extrapleural intrathoracic pacemaker, lung has developed normally.
References
MISCELLANEOUS
1. van Straten AH, Firanescu C, Soliman Hamad MA, et al. Peripheral vascular disease as a predictor of survival after coronary artery bypass grafting: comparison with a matched general population. Ann Thorac Surg 2010;89:414 –20. 2. Birkmeyer JD, O’Connor GT, Quinton HB, et al. The effect of peripheral vascular disease on in-hospital mortality rates with coronary artery bypass surgery. Northern New England Cardiovascular Disease Study Group. J Vasc Surg 1995;21: 445–52. 3. Saxena P, Newman MA, Shehatha JS, Redington AN, Konstantinov IE. Remote ischemic conditioning: evolution of the concept, mechanisms, and clinical application. J Card Surg 2010;25:127–34. 4. Birnbaum Y, Hale SL, Kloner RA. Ischemic preconditioning at a distance: reduction of myocardial infarct size by partial reduction of blood supply combined with rapid stimulation of the gastrocnemius muscle in the rabbit. Circulation 1997;96: 1641– 6. 5. Shimizu M, Tropak M, Diaz RJ, et al. Transient limb ischaemia remotely preconditions through a humoral mechanism acting directly on the myocardium: evidence suggesting cross-species protection. Clin Sci (Lond) 2009;117:191–200. © 2011 by The Society of Thoracic Surgeons Published by Elsevier Inc
Fig 2. The system was changed to an endocardial pacemaker system. The previous epicardial lead has been left in situ. 0003-4975/$36.00
Ann Thorac Surg 2011;91:330 – 6
Krishnan Ganapathy Subramaniam, MCh Ravi Agarwal, MCh Kotturathu Mammen Cherian, FRACS, DSc Cardiac Surgery Frontier Lifeline R-30-C Ambattur Industrial Estate Rd Mogappair, Chennai Tamil Nadu, India 600101 e-mail: [email protected]
References 1. Agarwal R, Krishnan GS, Abraham S, et al. Extrapleural intrathoracic implantation of permanent pacemaker in the pediatric age group. Ann Thorac Surg 2007;83:1549 –52. 2. Roubertie F, Bret EL, Thambo JB, Roques X. Intradiaphragmatic pacemaker implantation in very low weight premature neonate. Interact Cardio Vasc Thorac Surg 2009;9: 743– 4.
Stereotactic Lung Radiotherapy: Do We Need Fiducial Markers? To the Editor: We read with interest the article by Harley and colleagues [1] on using endobronchial ultrasound and navigational bronchoscopy to place fiducial markers (FMs) for tumor tracking during stereotactic radiotherapy. Their approach resulted in fewer complications than percutaneous FM placement, and more importantly, improved nodal staging. The latter is essential because occult nodal metastases can occur in 10% of patients with negative nodes on the basis of computed tomography (CT) and positron emission tomography scans [2]. However, their discussion on strategies for managing tumor motion is not a true reflection of the state of the art in radiotherapy. Comments that merit particular attention are that “linear-accelerator based stereotactic treatments are inadequate and will result in larger treatment margins and associated lung damage than treatment with CyberKnife” (Accuray, Sunnyvale, CA) and that a system which does not require FMs for delivering stereotactic treatments has not been developed, suggesting that tumor tracking is a fundamental component of stereotactic lung radiotherapy. Four-dimensional CT scans have been used since 2003 to account for tumor motion in planning lung stereotactic radiotherapy. Studies of 4-dimensional CT reveal that only a minority of lung tumors move more than 1 cm and that a single scan can reliably identify this [3, 4]. Consequently, most peripheral tumors do not require respiration-gated radiotherapy or tracking to minimize toxicity. Modern linear accelerators are equipped with a cone-beam CT scan, a device that permits the 3-dimensional tumor position to be established immediately before and © 2011 by The Society of Thoracic Surgeons Published by Elsevier Inc
335
during treatment. Cone-beam CT allows the daily treatment setup to be based on the actual tumor position, thereby avoiding the toxicity and costs of implanting FMs. At present, real-time motion tracking only appears to be essential when treatment delivery times are prolonged to more than 30 minutes [5]. This is clearly the case with the CyberKnife (Accuray), because the median treatment delivery time for lung treatments is 1 hour 40 minutes (range, 47 minutes to 3 hours 30 minutes) [6]. In comparison, use of volumetric modulated arc therapy permits treatment delivery on a linear accelerator in less than 12 minutes after position verification using cone-beam CT [7]. Software for volumetric modulated arc therapy delivery is currently being offered by a number of manufacturers, and this allows for faster delivery that minimizes the risk of intratreatment drifts in tumor position and improves patient tolerance and departmental efficiency [7]. Finally, and most importantly to patients, the results reported using CyberKnife (Accuray) do not appear to be superior in terms of tumor control or toxicity than those planned using 4-dimensional CT scans and delivered on linear accelerators [8]. We agree with the authors that patients should be evaluated by a multidisciplinary team and that endoscopic staging of the mediastinum and hilus should be considered essential for stereotactic radiotherapy. However, we question the necessity of FMs, given the frail patient population, need for general anesthetic, cost, 10% miss rate, and small pneumothorax risk. This importance of these risks is magnified because stereotactic treatments are being delivered routinely without FMs on linear accelerators with outstanding oncologic outcomes and very favorable toxicity.
The VU University Medical Centre has a research collaboration with Varian Medical Systems Inc, and Dr Palma’s research is supported by the Canadian Association of Radiation Oncologists Elekta Research Fellowship. Suresh Senan, FRCR, PhD David Palma, MD, FRCPC Department of Radiotherapy VU University Medical Centre De Boelelaan 1117 1007 MB Amsterdam The Netherlands e-mail: [email protected]
References 1. Harley DP, Krimsky WS, Sarkar S, Highfield D, Aygun C, Gurses B. Fiducial marker placement using endobronchial ultrasound and navigational bronchoscopy for stereotactic radiosurgery: an alternative strategy. Ann Thorac Surg 2010; 89:368 –74. 2. Herth FJ, Eberhardt R, Krasnik M, Ernst A. Endobronchial ultrasound-guided transbronchial needle aspiration of lymph nodes in the radiologically and positron emission tomography-normal mediastinum in patients with lung cancer. Chest 2008;133:887–91. 3. Liu HH, Balter P, Tutt T, et al. Assessing respiration-induced tumor motion and internal target volume using fourdimensional computed tomography for radiotherapy of lung cancer. Int J Radiat Oncol Biol Phys 2007;68:531– 40. 4. van der Geld YG, Lagerwaard FJ, van Sornsen de Koste JR, et al. Reproducibility of target volumes generated using uncoached 4-dimensional CT scans for peripheral lung cancer. Radiat Oncol 2006;1:43. 0003-4975/$36.00
MISCELLANEOUS
One of the concerns raised for the first approach was that it might interfere with lung development. We recently explanted one such epicardial extrapleural pacemaker that was placed when the child was 2.5 kg and converted it to an endocardial lead with the generator changed to a infraclavicular location when the child was 15 kg. There was no interference with the pulmonary development or respiratory mechanics, and the generator could easily be explanted though the previous incision without entering the pleural cavity (Figs 1 and 2).
CORRESPONDENCE
CORRESPONDENCE
grafting (CABG). We read this article with extreme interest and would like to add some comments on the topic. The prognosis of patients with PAD is related to the presence and extent of underlying coronary arterial disease (CAD). Because PAD is associated with more severe and extensive CAD, it is well known that PAD is an independent predictor of poor long-term survival among patients undergoing CABG [1, 2]. However, the topic of short–term mortality after CABG is debatable. Although numerous studies have demonstrated adverse short-term outcomes among patients with PAD who undergo CABG [2], the present study reports that PAD does not affect early outcomes in patients who undergo CABGs. We believe that one of the mechanisms of this interesting finding may be remote ischemic preconditioning (RIPC). Cardioprotection was first conceived in the late 1980s and has evolved to include endogenous cardioprotective ischemic preconditioning, which protects the heart from an episode of acute lethal ischemia–reperfusion injury by applying brief nonlethal episodes of ischemia. Later it was shown that brief, controlled episodes of intermittent ischemia of the arm or leg may confer powerful protection against prolonged ischemia in a distant organ; thus, the concept of RIPC is now popular [3]. In 1997, Birnbaum and colleagues [4] published the first study suggesting that transient limb ischemia could remotely precondition the ischemic heart. Subsequently, RIPC induced by transient limb ischemia was shown to reduce ischemic myocardial damage during CABG [5]. In the present study, RIPC triggered by intermittent claudication secondary to PAD may be responsible for preventing early mortality after CABG. First described almost 15 years ago, this concept has been slow to translate into clinical practice. We believe that clinical applicability should be further studied in large, multi-center randomized trials.
Ann Thorac Surg 2011;91:330 – 6
Extrapleural Intrathoracic Pacemaker for Congenital Heart Block To the Editor: We had previously reported our experience with extrapleural intrathoracic pacemaker implantation in children and low birthweight infants [1]. This approach has the advantages of a single incision for lead and generator placement, security of the generator under the thoracic cage, and less chance of lead fracture. Another recently suggested option in a 1.3-kg child has been to place the generator between the parietal pericardium and diaphragm muscle [2].
Ozcan Ozeke, MD Mutlu Gungor, MD Can Ozer, MD Department of Cardiology Bayindir Hospital Kardiyoloji Klinigi, Sögütözü Ankara, 06520 Turkey e-mail: [email protected]
Fig 1. The previously placed extrapleural intrathoracic pacemaker, lung has developed normally.
References
MISCELLANEOUS
1. van Straten AH, Firanescu C, Soliman Hamad MA, et al. Peripheral vascular disease as a predictor of survival after coronary artery bypass grafting: comparison with a matched general population. Ann Thorac Surg 2010;89:414 –20. 2. Birkmeyer JD, O’Connor GT, Quinton HB, et al. The effect of peripheral vascular disease on in-hospital mortality rates with coronary artery bypass surgery. Northern New England Cardiovascular Disease Study Group. J Vasc Surg 1995;21: 445–52. 3. Saxena P, Newman MA, Shehatha JS, Redington AN, Konstantinov IE. Remote ischemic conditioning: evolution of the concept, mechanisms, and clinical application. J Card Surg 2010;25:127–34. 4. Birnbaum Y, Hale SL, Kloner RA. Ischemic preconditioning at a distance: reduction of myocardial infarct size by partial reduction of blood supply combined with rapid stimulation of the gastrocnemius muscle in the rabbit. Circulation 1997;96: 1641– 6. 5. Shimizu M, Tropak M, Diaz RJ, et al. Transient limb ischaemia remotely preconditions through a humoral mechanism acting directly on the myocardium: evidence suggesting cross-species protection. Clin Sci (Lond) 2009;117:191–200. © 2011 by The Society of Thoracic Surgeons Published by Elsevier Inc
Fig 2. The system was changed to an endocardial pacemaker system. The previous epicardial lead has been left in situ. 0003-4975/$36.00
Ann Thorac Surg 2011;91:330 – 6
Krishnan Ganapathy Subramaniam, MCh Ravi Agarwal, MCh Kotturathu Mammen Cherian, FRACS, DSc Cardiac Surgery Frontier Lifeline R-30-C Ambattur Industrial Estate Rd Mogappair, Chennai Tamil Nadu, India 600101 e-mail: [email protected]
References 1. Agarwal R, Krishnan GS, Abraham S, et al. Extrapleural intrathoracic implantation of permanent pacemaker in the pediatric age group. Ann Thorac Surg 2007;83:1549 –52. 2. Roubertie F, Bret EL, Thambo JB, Roques X. Intradiaphragmatic pacemaker implantation in very low weight premature neonate. Interact Cardio Vasc Thorac Surg 2009;9: 743– 4.
Stereotactic Lung Radiotherapy: Do We Need Fiducial Markers? To the Editor: We read with interest the article by Harley and colleagues [1] on using endobronchial ultrasound and navigational bronchoscopy to place fiducial markers (FMs) for tumor tracking during stereotactic radiotherapy. Their approach resulted in fewer complications than percutaneous FM placement, and more importantly, improved nodal staging. The latter is essential because occult nodal metastases can occur in 10% of patients with negative nodes on the basis of computed tomography (CT) and positron emission tomography scans [2]. However, their discussion on strategies for managing tumor motion is not a true reflection of the state of the art in radiotherapy. Comments that merit particular attention are that “linear-accelerator based stereotactic treatments are inadequate and will result in larger treatment margins and associated lung damage than treatment with CyberKnife” (Accuray, Sunnyvale, CA) and that a system which does not require FMs for delivering stereotactic treatments has not been developed, suggesting that tumor tracking is a fundamental component of stereotactic lung radiotherapy. Four-dimensional CT scans have been used since 2003 to account for tumor motion in planning lung stereotactic radiotherapy. Studies of 4-dimensional CT reveal that only a minority of lung tumors move more than 1 cm and that a single scan can reliably identify this [3, 4]. Consequently, most peripheral tumors do not require respiration-gated radiotherapy or tracking to minimize toxicity. Modern linear accelerators are equipped with a cone-beam CT scan, a device that permits the 3-dimensional tumor position to be established immediately before and © 2011 by The Society of Thoracic Surgeons Published by Elsevier Inc
335
during treatment. Cone-beam CT allows the daily treatment setup to be based on the actual tumor position, thereby avoiding the toxicity and costs of implanting FMs. At present, real-time motion tracking only appears to be essential when treatment delivery times are prolonged to more than 30 minutes [5]. This is clearly the case with the CyberKnife (Accuray), because the median treatment delivery time for lung treatments is 1 hour 40 minutes (range, 47 minutes to 3 hours 30 minutes) [6]. In comparison, use of volumetric modulated arc therapy permits treatment delivery on a linear accelerator in less than 12 minutes after position verification using cone-beam CT [7]. Software for volumetric modulated arc therapy delivery is currently being offered by a number of manufacturers, and this allows for faster delivery that minimizes the risk of intratreatment drifts in tumor position and improves patient tolerance and departmental efficiency [7]. Finally, and most importantly to patients, the results reported using CyberKnife (Accuray) do not appear to be superior in terms of tumor control or toxicity than those planned using 4-dimensional CT scans and delivered on linear accelerators [8]. We agree with the authors that patients should be evaluated by a multidisciplinary team and that endoscopic staging of the mediastinum and hilus should be considered essential for stereotactic radiotherapy. However, we question the necessity of FMs, given the frail patient population, need for general anesthetic, cost, 10% miss rate, and small pneumothorax risk. This importance of these risks is magnified because stereotactic treatments are being delivered routinely without FMs on linear accelerators with outstanding oncologic outcomes and very favorable toxicity.
The VU University Medical Centre has a research collaboration with Varian Medical Systems Inc, and Dr Palma’s research is supported by the Canadian Association of Radiation Oncologists Elekta Research Fellowship. Suresh Senan, FRCR, PhD David Palma, MD, FRCPC Department of Radiotherapy VU University Medical Centre De Boelelaan 1117 1007 MB Amsterdam The Netherlands e-mail: [email protected]
References 1. Harley DP, Krimsky WS, Sarkar S, Highfield D, Aygun C, Gurses B. Fiducial marker placement using endobronchial ultrasound and navigational bronchoscopy for stereotactic radiosurgery: an alternative strategy. Ann Thorac Surg 2010; 89:368 –74. 2. Herth FJ, Eberhardt R, Krasnik M, Ernst A. Endobronchial ultrasound-guided transbronchial needle aspiration of lymph nodes in the radiologically and positron emission tomography-normal mediastinum in patients with lung cancer. Chest 2008;133:887–91. 3. Liu HH, Balter P, Tutt T, et al. Assessing respiration-induced tumor motion and internal target volume using fourdimensional computed tomography for radiotherapy of lung cancer. Int J Radiat Oncol Biol Phys 2007;68:531– 40. 4. van der Geld YG, Lagerwaard FJ, van Sornsen de Koste JR, et al. Reproducibility of target volumes generated using uncoached 4-dimensional CT scans for peripheral lung cancer. Radiat Oncol 2006;1:43. 0003-4975/$36.00
MISCELLANEOUS
One of the concerns raised for the first approach was that it might interfere with lung development. We recently explanted one such epicardial extrapleural pacemaker that was placed when the child was 2.5 kg and converted it to an endocardial lead with the generator changed to a infraclavicular location when the child was 15 kg. There was no interference with the pulmonary development or respiratory mechanics, and the generator could easily be explanted though the previous incision without entering the pleural cavity (Figs 1 and 2).
CORRESPONDENCE