CASE REPORTS
Right Vocal-Cord Paralysis after Open-Heart Operation Karl L. Horn, M.D., and Jacob Abouav, M.D. ABSTRACT We report a previously unrecorded complication of open-heart operations and discuss the cause. Suggestions for effectively eliminating this complication are offered.
Unilateral vocal-cord paralysis after thoracic surgery is a rare but well-documented entity (1, 2, 8, 10). The mechanism of paralysis is injury to the intrathoracic portion of the recurrent laryngeal nerve. The left recurrent laryngeal nerve, with its longer intrathoracic course, is involved most often. Review of the literature does not reveal any reports of vocal cord paralysis following open-heart operation. We have observed 4 patients with transient vocalcord paralysis in a series of 193 patients who underwent an open-heart operation. In 1of the 4 patients, the procedure involved insertion of a prosthetic valve and in the other 3, aortocoronary bypass. In all 4 patients, the paralysis was unilateral and on the right side. One representative case report is presented to illustrate this unusual complication. The mechanism of injury is described to distinguish it from the left vocal-cord paralysis that occurs in other thoracic surgical procedures.
The patient underwent a double saphenous vein aortocoronary bypass without complication. He was extubated at twenty-four hours but after extubation complained of hoarseness and dysphonia for six days. On the seventh day, indirect laryngoscopy revealed partial paralysis and decreased mobility of the right vocal cord. No inflammation, ulceration, or granulation was noted. The patient was discharged on the fourteenth postoperative day. Follow-up six weeks after operation revealed normal mobility of both vocal cords and no hoarseness. The patient has remained asymptomatic.
Comment Injury to the recurrent laryngeal nerve is reported most often following operation on the neck, especially thyroidectomy. A less frequent site of injury to these nerves is in the thorax [l, 2, 8, 101. The intrathoracic segment of the right recurrent laryngeal nerve is quite short since it leaves the vagus nerve at the level of the subclavian artery, around which it turns to ascend into the neck [91. The left recurrent laryngeal nerve leaves the vagus nerve at a point just below the aortic arch. Because the nerve courses A 57-year-old man was admitted to the hospital around this vessel, its intrathoracic segment is with a two-year history of increasing angina longer and more vulnerable to direct injury pectoris. Stress electrocardiogram revealed than the corresponding segment on the right chest pain at stage I, with electrocardio- side. The different intrathoracic course of the graphic demonstration of S-T segment wave two recurrent laryngeal nerves would lead one depression after one minute at stage 11. to expect what has been reported in the surgical Coronary arteriography documented 95% oc- literature: vocal cord paralysis after thoracic clusion of the proximal left anterior descending surgery is almost always a left-sided lesion [l, coronary artery, proximal to the first perforator 2,8, 101. Accordingly, right vocal-cord paralysis branch, and 80% occlusion of the proximal following open-heart procedures is considered the exception rather than the rule. However, diagonal coronary artery (median branch). a more careful consideration of the surgical From the Department of Surgery, Mount Zion Hospital and procedures and of the anatomy of the recurMedical Center, San Francisco, CA. rent laryngeal nerves demonstrates why right Accepted for publication July 28, 1978. vocal-cord paralysis may occur after open-heart Address reprint requests to Dr. Abouav, Mount Zion Hos- operations. pital and Medical Center, 1600 Divisadero St, PO Box 7921, The brief duration of vocal cord paralysis San Francisco, CA 94120. 344 OOO3-4975/79/040344-03$01.25 @ 1978 by Karl L. Horn
345 Case Report: Horn and Abouav: Vocal-Cord Paralysis after Open-Heart Operation
following open-heart procedures indicates that it is caused by retraction or stretching of the right recurrent laryngeal nerve rather than by disruptive trauma, such as ligation, electrocoagulation, or cutting of the nerve fibers. The left recurrent laryngeal nerve, with its longer intrathoracic course, is more susceptible to trauma. In open-heart procedures, the right vocal-cord paralysis probably occurs because of a combination of two mechanisms that produce greater traction and stress upon the right recurrent laryngeal nerve. The first and probably the most important mechanism is median sternotomy retraction, which produces a lateral and anterior retraction of both subclavian arteries. Kirsh and associates [61 have implicated excessive spread of the median sternotomy retractor as the cause of brachial plexus damage in surgical procedures involving the heart. Since the right recurrent laryngeal nerve turns around the right subclavian artery, retraction of this vessel also retracts the nerve; the left nerve is unaffected by this procedure. The second mechanism is direct manipulation and retraction of the heart during open-heart procedures. Because both recurrent laryngeal nerves turn around major vessels, any inferior retraction upon the heart is transmitted directly to the nerves, stretching them with the vessels. Hook's law suggests that inferior retraction on the heart would produce more stress on the right recurrent laryngeal nerve than on the left [8]. This law states that the stress (force per area) set up within an elastic body is proportional to the strain (elongation per length) caused by the applied load [81. Thus, stress equals K (strain), where the constant K has a value characteristic of the elastic body, in our instance, the recurrent laryngeal nerve. Force -Area
Elongation Length
If it is assumed that the cross-sectional area of the two recurrent laryngeal nerves is equal and that inferior retraction on the heart results in essentially equal elongation of both recurrent laryngeal nerves, then the force applied to each nerve is inversely proportional to the length of the nerve. It follows that the shorter right nerve
has more force applied to its nerve fibers than does the left recurrent laryngeal nerve. The true incidence of vocal cord paralysis after open-heart operations remains unknown. In the present series, the incidence of right vocalcord paralysis is approximately 2%. This indicates that the threshold of the stretch injury necessary for damage to the right nerve is reached only occasionally. It is apparent that threshold of nerve damage is not reached on the left side during open-heart procedures. Avoiding excessive retraction has diminished this complication in the last two years. Another possible cause for vocal cord paralysis following open-heart operations merits brief mention: trauma secondary to endotracheal intubation. True vocal-cord paralysis following intubation is a relatively rare complication, and the incidence is certainly less than 2% [4, 5, 71. Although this complication may be seen as a unilateral paralysis, both cords are affected in equal incidence. It is unlikely that the present 4 instances of vocal cord paralysis were due to endotracheal intubation since the paralysis was specifically right-sided in each one. Finally, we suggest that there may be a higher incidence of injury to the right recurrent laryngeal nerve than has been reported. Transient postoperative hoarseness after open-heart operation, previously assumed to be caused by intralaryngeal injury, may indeed be caused by injury to the right recurrent laryngeal nerve. In the Cleveland Clinic series [4], 4 cases of postoperative hoarseness, 1 of which was permanent, were listed as postoperative complications of coronary artery bypass procedures.
References Baranyai L, Madarasz G: Recurrent nerve paralysis following lung surgery. J Thorac Cardiovasc Surg 46:531, 1963 Dedo HH: The paralyzed larynx: an electromyographic study in dogs and humans. Laryngoscope 80:1455, 1970 Hahn FW, Martin JT, Lillie JC: Vocal-cord paralysis with endotracheal intubation. Arch Otolaryngol 92:226, 1970 Hodgman JR, Cosgrove DM: Post hospital course and complications following coronary artery bypass. Cleve Clin Q 43:125, 1976
346 The Annals of Thoracic Surgery Vol 27 No 4 April 1979
5. Holley H, Gildea JE: Vocal cord paralysis after tracheal intubation. JAMA 215:281, 1971 6. Kirsh MM, Magee KR, Gag0 0, et al: Brachial plexus injury following median sternotomy incision. Ann Thorac Surg 11:315, 1971 7. Korman RM, Smith CP, Erwin JR: Acute laryngeal injury with short-term endotracheal anesthesia. Laryngoscope 83:683, 1973 8. Maassen W: Ergebnisse und Bedeutung der
Mediastinoskopie und anderer thoraxbioptischer Verfahren. Berlin, Springer-Verlag, 1967 9. Rustad WH, Morrison LF: Revised anatomy of the recurrent laryngeal nerves: surgical importance based on the dissection of 100 cadavers: a preliminary report. Laryngoscope 57237, 1952 10. Widstrom A: Palsy of the recurrent nerve following mediastinoscopy. Chest 67:365, 1975
Right Vocal-Cord Paralysis after Open-Heart Operation Karl L. Horn, M.D., and Jacob Abouav, M.D. ABSTRACT We report a previously unrecorded complication of open-heart operations and discuss the cause. Suggestions for effectively eliminating this complication are offered.
Unilateral vocal-cord paralysis after thoracic surgery is a rare but well-documented entity (1, 2, 8, 10). The mechanism of paralysis is injury to the intrathoracic portion of the recurrent laryngeal nerve. The left recurrent laryngeal nerve, with its longer intrathoracic course, is involved most often. Review of the literature does not reveal any reports of vocal cord paralysis following open-heart operation. We have observed 4 patients with transient vocalcord paralysis in a series of 193 patients who underwent an open-heart operation. In 1of the 4 patients, the procedure involved insertion of a prosthetic valve and in the other 3, aortocoronary bypass. In all 4 patients, the paralysis was unilateral and on the right side. One representative case report is presented to illustrate this unusual complication. The mechanism of injury is described to distinguish it from the left vocal-cord paralysis that occurs in other thoracic surgical procedures.
The patient underwent a double saphenous vein aortocoronary bypass without complication. He was extubated at twenty-four hours but after extubation complained of hoarseness and dysphonia for six days. On the seventh day, indirect laryngoscopy revealed partial paralysis and decreased mobility of the right vocal cord. No inflammation, ulceration, or granulation was noted. The patient was discharged on the fourteenth postoperative day. Follow-up six weeks after operation revealed normal mobility of both vocal cords and no hoarseness. The patient has remained asymptomatic.
Comment Injury to the recurrent laryngeal nerve is reported most often following operation on the neck, especially thyroidectomy. A less frequent site of injury to these nerves is in the thorax [l, 2, 8, 101. The intrathoracic segment of the right recurrent laryngeal nerve is quite short since it leaves the vagus nerve at the level of the subclavian artery, around which it turns to ascend into the neck [91. The left recurrent laryngeal nerve leaves the vagus nerve at a point just below the aortic arch. Because the nerve courses A 57-year-old man was admitted to the hospital around this vessel, its intrathoracic segment is with a two-year history of increasing angina longer and more vulnerable to direct injury pectoris. Stress electrocardiogram revealed than the corresponding segment on the right chest pain at stage I, with electrocardio- side. The different intrathoracic course of the graphic demonstration of S-T segment wave two recurrent laryngeal nerves would lead one depression after one minute at stage 11. to expect what has been reported in the surgical Coronary arteriography documented 95% oc- literature: vocal cord paralysis after thoracic clusion of the proximal left anterior descending surgery is almost always a left-sided lesion [l, coronary artery, proximal to the first perforator 2,8, 101. Accordingly, right vocal-cord paralysis branch, and 80% occlusion of the proximal following open-heart procedures is considered the exception rather than the rule. However, diagonal coronary artery (median branch). a more careful consideration of the surgical From the Department of Surgery, Mount Zion Hospital and procedures and of the anatomy of the recurMedical Center, San Francisco, CA. rent laryngeal nerves demonstrates why right Accepted for publication July 28, 1978. vocal-cord paralysis may occur after open-heart Address reprint requests to Dr. Abouav, Mount Zion Hos- operations. pital and Medical Center, 1600 Divisadero St, PO Box 7921, The brief duration of vocal cord paralysis San Francisco, CA 94120. 344 OOO3-4975/79/040344-03$01.25 @ 1978 by Karl L. Horn
345 Case Report: Horn and Abouav: Vocal-Cord Paralysis after Open-Heart Operation
following open-heart procedures indicates that it is caused by retraction or stretching of the right recurrent laryngeal nerve rather than by disruptive trauma, such as ligation, electrocoagulation, or cutting of the nerve fibers. The left recurrent laryngeal nerve, with its longer intrathoracic course, is more susceptible to trauma. In open-heart procedures, the right vocal-cord paralysis probably occurs because of a combination of two mechanisms that produce greater traction and stress upon the right recurrent laryngeal nerve. The first and probably the most important mechanism is median sternotomy retraction, which produces a lateral and anterior retraction of both subclavian arteries. Kirsh and associates [61 have implicated excessive spread of the median sternotomy retractor as the cause of brachial plexus damage in surgical procedures involving the heart. Since the right recurrent laryngeal nerve turns around the right subclavian artery, retraction of this vessel also retracts the nerve; the left nerve is unaffected by this procedure. The second mechanism is direct manipulation and retraction of the heart during open-heart procedures. Because both recurrent laryngeal nerves turn around major vessels, any inferior retraction upon the heart is transmitted directly to the nerves, stretching them with the vessels. Hook's law suggests that inferior retraction on the heart would produce more stress on the right recurrent laryngeal nerve than on the left [8]. This law states that the stress (force per area) set up within an elastic body is proportional to the strain (elongation per length) caused by the applied load [81. Thus, stress equals K (strain), where the constant K has a value characteristic of the elastic body, in our instance, the recurrent laryngeal nerve. Force -Area
Elongation Length
If it is assumed that the cross-sectional area of the two recurrent laryngeal nerves is equal and that inferior retraction on the heart results in essentially equal elongation of both recurrent laryngeal nerves, then the force applied to each nerve is inversely proportional to the length of the nerve. It follows that the shorter right nerve
has more force applied to its nerve fibers than does the left recurrent laryngeal nerve. The true incidence of vocal cord paralysis after open-heart operations remains unknown. In the present series, the incidence of right vocalcord paralysis is approximately 2%. This indicates that the threshold of the stretch injury necessary for damage to the right nerve is reached only occasionally. It is apparent that threshold of nerve damage is not reached on the left side during open-heart procedures. Avoiding excessive retraction has diminished this complication in the last two years. Another possible cause for vocal cord paralysis following open-heart operations merits brief mention: trauma secondary to endotracheal intubation. True vocal-cord paralysis following intubation is a relatively rare complication, and the incidence is certainly less than 2% [4, 5, 71. Although this complication may be seen as a unilateral paralysis, both cords are affected in equal incidence. It is unlikely that the present 4 instances of vocal cord paralysis were due to endotracheal intubation since the paralysis was specifically right-sided in each one. Finally, we suggest that there may be a higher incidence of injury to the right recurrent laryngeal nerve than has been reported. Transient postoperative hoarseness after open-heart operation, previously assumed to be caused by intralaryngeal injury, may indeed be caused by injury to the right recurrent laryngeal nerve. In the Cleveland Clinic series [4], 4 cases of postoperative hoarseness, 1 of which was permanent, were listed as postoperative complications of coronary artery bypass procedures.
References Baranyai L, Madarasz G: Recurrent nerve paralysis following lung surgery. J Thorac Cardiovasc Surg 46:531, 1963 Dedo HH: The paralyzed larynx: an electromyographic study in dogs and humans. Laryngoscope 80:1455, 1970 Hahn FW, Martin JT, Lillie JC: Vocal-cord paralysis with endotracheal intubation. Arch Otolaryngol 92:226, 1970 Hodgman JR, Cosgrove DM: Post hospital course and complications following coronary artery bypass. Cleve Clin Q 43:125, 1976
346 The Annals of Thoracic Surgery Vol 27 No 4 April 1979
5. Holley H, Gildea JE: Vocal cord paralysis after tracheal intubation. JAMA 215:281, 1971 6. Kirsh MM, Magee KR, Gag0 0, et al: Brachial plexus injury following median sternotomy incision. Ann Thorac Surg 11:315, 1971 7. Korman RM, Smith CP, Erwin JR: Acute laryngeal injury with short-term endotracheal anesthesia. Laryngoscope 83:683, 1973 8. Maassen W: Ergebnisse und Bedeutung der
Mediastinoskopie und anderer thoraxbioptischer Verfahren. Berlin, Springer-Verlag, 1967 9. Rustad WH, Morrison LF: Revised anatomy of the recurrent laryngeal nerves: surgical importance based on the dissection of 100 cadavers: a preliminary report. Laryngoscope 57237, 1952 10. Widstrom A: Palsy of the recurrent nerve following mediastinoscopy. Chest 67:365, 1975
