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Two-dimensional echocardiography in cardiac tamponade occurring after cardiac surgery
1250
JACC Vol. 5, No.5 May 1985:1250-2
Two-Dimensional Echocardiography in Cardiac Tamponade Occurring After Cardiac Surgery IVAN A. D'CRUZ, MD, FACC, KENNETH KENSEY, MD, CHARLES CAMPBELL, MD, ROBERT REPLOGLE, MD, MUKESH JAIN, MD, FACC Chicago, Illinois
Cardiac tamponade is an important comphcation after cardiac surgery, yet little has been published on the echocardiographic diagnosis of this situation. The twodimensional echocardiograms of 11 patients who required surgical relief of cardiac tamponade complicating cardiac surgery were therefore reviewed. Four had nonloculated pericardial effusions surrounding both ventricles. The other seven patients had a loculated posterior pericardial effusion; in three of these the effusion altered left ventricular posterior wall contour so that it was concave toward the effusion ill the long-axis view; in two, a strikingly abnormal motion of the left ventricular
Various echocardiographic manifestations of cardiac tamponade have been described over the last decade (1-5). In almost all of these reports, tamponade was associated with a large nonloculated pericardial effusion that surrounded the ventricles on all sides and usually also extended behind both atria. Cardiac tamponade is an important life-threatening and not uncommon complication after open heart surgery (6-10) and is often associated with loculated' pericardial effusions. Yet its echocardiographic presentation has hitherto received relatively little attention. Therefore, we studied the twodimensional echocardiograms of a series of patients who underwent reoperation for relief of cardiac tamponade after open heart surgery,
Methods Patient selection. Over a 4 year period, 19 patients who had had open heart surgery at Michael Reese Hospital underwent reoperation for relief of tamponade 3 to 42 days after Frsrn the Division of Cardiology and Cardiac Surgery, Michael Reese Hospital and Medical Center and University of Chicago Pritzker School of Medicine, Chicago, Illinois. Manuscript received August 13, 1984; revised manuscript received November 13. 1984, accepted December 5, 1984. Address for reprints: Ivan A. D'Cruz, MD, Cardiology Division, Michael Reese Hospital and Medical Center, Lake Shore Drive at 31st Street. Chicago, Illinois 60616. © 1985 by the American College of Cardiology
posterior wall was noted, such that the width of the posterior pericardial space diminished in systole and widened abruptly in early diastole. The quantity of pericardial contents (fluid, blood or clot) evacuated surgically was smaller titan usually encountered' in patients with tamponade due to various "medical" cOnditions. Thus, unlike tamponade with other perlcardial effusions, tamponade after cardiac su~gery is due to a pericardial effusion that is smaller in volume, often loculated posteriorly and associated with certain unique two-dimensional echocardiographic features. (J Am Coli Cardiol 1985;5:1250-2)
operation. Two-dimensional echocardiography was per-' formed in II of these patients using a wide angle mechanical sector scanner (Advanced Technical Laboratories). This series of II patients comprised 7 men and 4 women, whose ages ranged from 31 to 73 years (mean 59). The original cardiac operation was coronary artery bypass grafting in eight, mitral valve replacement in two and atrial septal defect repair in one. Evidence of tamponade. Echocardiography was performed after clinical signs of tamponade had developed and usually preceded surgical relief of tamponade by less than a few hours. In all cases, after an initial postoperative period with stable signs, the following evidence for tamponade was observed: 1) decrease in systemic blood pressure, with increase in jugular venous pressure, tachycardia and respiratory distress; and 2) after removal of the pericardial contents, an immediate substantial increase in blood pressure (mean increase 45 mm Hg), with concomitant increase in pulse pressure, decrease in venous pressure and improvement in general cardiac status. A paradoxical P41se (varying from 15 to 40 mm Hg) was noted in six patients, including all four patients with a nonloculated pericardial effusion, but only two of those with a loculated posterior effusion.
Results Relief of tamponade. The pericardial contents, removed surgically, varied from 180 to 700 ml in volume, 0735-1097/85/$3.30
lACC Vol. 5, No.5
D'CRUZ ET AL. ECHOCARDJOGRAPHY IN POSTOPERATIVE TAMPONADE
May 1985:125G-2
and in appearance consisted of bloodstained pericardial fluid, unclotted recently extravasated blood, "old" dark blood or blood clots or various combinations of these. The case of a 64 year old man is worth reporting in detail. He had been on Coumadin therapy because of pulmonary embolism complicating the postoperative course after coronary bypass surgery. He was readmitted 6 weeks after his initial surgery for chest discomfort and dyspnea. Prothrombin time then was 24 seconds (control 12 seconds). The two-dimensional echocardiogram demonstrated a large loculated pericardial effusion (Fig. 1). A few hours later, the patient rapidly became hypotensive. Swan-Ganz catheterization revealed pressures (mm Hg) as follows: right atrium, mean = 15, a wave = 25, v wave = 15; right ventricle = 42115; pulmonary artery = 42120; pulmonary artery wedge, mean = 20, a wave = 20, v wave = 39. Emergency surgical drainage of the loculated pericardial effusion was promptly scheduled. In the operating room, immediately before subcostal drainage of the pericardial effusion, the pressures (mm Hg) were: central venous, 20; pulmonary artery wedge, 30; mean arterial, 60. Four hundred ml of bloody fluid were removed, and immediately thereafter pressures (mm Hg) were: central venous, 10; pulmonary artery wedge, 15; mean arterial, 95 (systolic 128, diastolic 60). These pressures remained essentially unchanged over the next 48 hours. Echocardiographic findings. A moderate to large nonloculated pericardia I effusion was noted in four patients. Pericardial fluid was visualized anterior and posterior to the heart, as well as posterior to both atria. Some abnormal pendulous cardiac motion was present, but neither extreme
ENODIASTOLE
SYSTOLE
"swinging" cardiac motion nor alternation of cardiac position was observed. Excessive inward motion (indentation) of the right atrial wall (5) was noted in two of the four patients. Phasic reciprocal changes with respiration in right and left ventricular size (1,3) could be identified in all four patients when the videotape was reviewed in slow motion or in frame by frame sequence. In the other seven patients. the pericardial fluid was loculated posteriorly behind the left ventricle. No pericardial fluid was visualized anterior to the heart, even with the patient sitting upright. Phasic respiratory changes in ventricular dimensions were not present. In these patients, the contour of the left ventricular and atrial posterior wall was abnormal: convex to the left ventricular chamber, concave toward the posterior pericardial effusion. In two patients with a loculated pericardial effusion. a strikingly unusual motion of the left ventricular posterior wall and behavior of the posterior pericardial space was observed in long-axis as well as short-axis views: the posterior pericardial space decreased in width in systole and abruptly increased in width in diastole (Fig. I). In diastole, the left ventricular posterior wall moved abruptly anteriorly; concomitantly the left ventricular dimension decreased. A decrease in left ventricular cavity width in diastole was evident in long-axis, short-axis and apical four chamber views. The systolic and diastolic phases of the cardiac cycle were identified with reference to mitral valve motion and the simultaneously recorded electrocardiogram. Such' 'paradoxical' , motion of the left ventricular posterior wall is the reverse of what is usually noted in patients with a pericardial effusion of moderate size. Systolic posterior motion of the
WID DIASTOLE
APICAl 1.0 GAXI S
(f!J. v
LV
trT
1251
Figure 1. Two-dimensional echocardiogram of a patient with postoperative pericardial effusion (EFF) showing serial frames from the same cardiac cycle in the apical long-axis view (top row), the apical four chamber view (middle row) and parasternal short-axis view (bottom row). In each row, the left frame is at enddiastole, the center frame in systole and the right frame in mid-diastole.The phases of the cardiac cycle were identified with reference to motion of the mitral valve and to the simultaneously recorded electrocardiogram. A large loculated pericardial effusion is seen posterior and posterolateral to the heart, with virtually no effusion anteriorly. Note that the pericardial effusion appears wider at mid-diastole (than during systole), and that this is associated with decreased width and altered shape of the left ventricle (LV), which becomes more concave toward the loculated pericardial effusion. LA = left atrium; PER = pericardium; RV = right ventricle.
1252
D'CRUZ ET AL. ECHOCARDIOGRAPHY IN POSTOPERATIVE TAMPONADE
left ventricular wall may be noted in association with a large pericardial effusion and "swinging" heart, but in our patients there was no cardiac swinging because the heart was tethered anteriorly by pericardial adhesions. In addition to the 11 patients requiring reoperation for tamponade. I patient developed mild tamponade due to a nonloculated pericardial effusion 3 days after coronary bypass surgery and was managed conservatively. Serial echocardiograms during the next 4 days demonstrated a gradual decrease of the pericardial effusion and regression of clinical signs of tamponade.
lACC Vol. 5, No.5 May 1985:1250-2
respiratory changes in ventricular dimensions (1,3), right ventricular narrowing (2) or abnormal motion of the right ventricular or right atrial wall (4,5). These ultrasound signs of tamponade were present in varying degree in the four patients in our series who had a nonloculated pericardial effusion, with pericardial fluid freely distributed all around both ventricles and also behind both atria. We are indebted to Karl T. Weber, MD, Director, Cardiology Division, Michael Reese Hospital for helpfully reviewing this manuscript.
References Discussion Pericardial effusion causing cardiac tamponade is not uncommon after cardiac surgery. Although it is most frequently encountered in the immediate postoperative period, Jones et al. (II) collected 43 instances of late postoperative tamponade (7 days to 3 months after cardiac surgery) reported before 1979. Loculated pericardial effusions causing tamponade. Echocardiography has been found useful in detecting a loculated posterior pericardial effusion presenting with tamponade after surgery (9-11). Seven of our patients with tamponade after surgery had a posterior loculated pericardial effusion. Postoperative loculated pericardial effusions causing tamponade by selective compression of the left atrium (12), right ventricular outflow area (13) and right atrium (14, IS) have been described. Dunlap et al. (16) presented echocardiographic and hemodynamic data indicating cardiac compression in a 25 year old man who had a posttraumatic massive organized pericardial hematoma posterior to the heart. Abnormal left ventricular wall motion. To our knowledge, the type of abnormal left ventricular posterior wall motion noted in two of our patients (Fig. I) has not been described before, although it seems present in the M-mode echocardiograms of a patient described by Jones et al. (11) (their Fig. 2). The posterior pericardial space appears to expand in early diastole, and narrow during systole, the reverse of what is usually observed in pericardial effusions. It is likely that this finding and the concave contour of the left ventricular and atrial posterior wall, noted in some of our patients with a loculated posterior pericardial effusion, is due to the high pressure in such effusions. This deformation of the left heart shape may be expected to be less prominent during systole than in diastole; this, in fact, is what was observed on two-dimensional echocardiography. Tamponade complicating various "medical" causes of pericarditis is usually caused by nonloculated pericardial effusions, and manifests echocardiographically by phasic
I. D'Cruz lA, Cohen HC, Prabhu R, Glick G. Diagnosis of cardiac tamponade by echocardiography: changes in mitral valve motion and ventricular dimensions with special reference to paradoxical pulse. Circulation 1975;52:460-6.
2. Schiller NB, Botvinick EH. Right ventricular compression as a sign of cardiac tamponade. An analysis of echocardiographic dimensions and their clinical implication. Circulation 1977;56:774-9. 3. Steele HP, Adolph Rl, Fowler NO. Echocardiographic study of cardiac tamponade. Circulation 1977;56:951-9. 4. Armstrong WF, Schilt BF, Helper nr, Dillon lE, Feigenbaum H. Diastolic collapse of the right ventricle with cardiac tamponade: an echocardiographic study. Circulation) 982;65: 1491-6. 5. Gillam LD, Guyer D, Gibson TC, King ME, Marshall 1, Weyman AE. Hydrodynamic compression of the right atrium: a new echocardiographic sign of cardiac tamponade. Circulation 1983;68:294-301. 6. Nelson RM, lenson CB, Smoot WM. Pericardial tamponade following open-heart surgery. 1 Thorac Cardiovasc Surg 1969;58:510-6. 7. Prewitt TA, Rackley CE, Wilcox BR, Scatlift JH, Young DT. Cardiac tamponade as a late complication of open-heart surgery. Am Heart J 1968;76:139-41. 8. SCOII RAP, Drew CEo Delayed pericardial effusion with tamponade after cardiac surgery. Br Heart 11973;35:1304-6. 9. Merrill W, Donahoo JS, Brawley RK, Taylor D. Late cardiac tamponade. A potentially lethal complication of open-heart surgery. J Thorac Cardiovasc Surg 1976;72:929-32. 10. Fernando HA, Friedman HS, Legam F, Sakurai H. Late cardiac tamponade following open-heart surgery. Detection by echocardiography. Ann Thorac Surg 1977;24:174-7. II. Jones MR, Vine DL, Alias M, Todd EP. Late isolated left ventricular tamponade. Clinical, hemodynamic and echocardiographic manifestations of a previously unreported postoperative complication. J Thorac Cardiovasc Surg 1979;77:142-6. 12. Yacoub MH, Cleland WP, Deal CWo Left atrial tamponade. Thorax 1966;21:205-9. 13. Hill 10, Johnson DC, Miller GE, Kwith WJ, Gerbode F. Latent mediastinal tamponade after open-heart surgery. Arch Surg 1969;19:808-14. 14. Kronzon I, Cohen ML, Winer HE. Cardiac tamponade by loculated pericardial hematoma: limitations of M-mode echocardiography. J Am Coli Cardiol 1983;3:913-5. 15. Young SC, Gregoratos G, Swain lA, Joyo CI. Delayed postoperative cardiac tamponade mimicking severe tricuspid valve stenosis. Chest 1984;85:824-6. 16. Dunlap TE, Sorkin RP, Mori KW, Popat KD. Massive organized intrapericardial hematoma mimicking constrictive pericarditis. Am Heart J 1982;104: 1373-5.
JACC Vol. 5, No.5 May 1985:1250-2
Two-Dimensional Echocardiography in Cardiac Tamponade Occurring After Cardiac Surgery IVAN A. D'CRUZ, MD, FACC, KENNETH KENSEY, MD, CHARLES CAMPBELL, MD, ROBERT REPLOGLE, MD, MUKESH JAIN, MD, FACC Chicago, Illinois
Cardiac tamponade is an important comphcation after cardiac surgery, yet little has been published on the echocardiographic diagnosis of this situation. The twodimensional echocardiograms of 11 patients who required surgical relief of cardiac tamponade complicating cardiac surgery were therefore reviewed. Four had nonloculated pericardial effusions surrounding both ventricles. The other seven patients had a loculated posterior pericardial effusion; in three of these the effusion altered left ventricular posterior wall contour so that it was concave toward the effusion ill the long-axis view; in two, a strikingly abnormal motion of the left ventricular
Various echocardiographic manifestations of cardiac tamponade have been described over the last decade (1-5). In almost all of these reports, tamponade was associated with a large nonloculated pericardial effusion that surrounded the ventricles on all sides and usually also extended behind both atria. Cardiac tamponade is an important life-threatening and not uncommon complication after open heart surgery (6-10) and is often associated with loculated' pericardial effusions. Yet its echocardiographic presentation has hitherto received relatively little attention. Therefore, we studied the twodimensional echocardiograms of a series of patients who underwent reoperation for relief of cardiac tamponade after open heart surgery,
Methods Patient selection. Over a 4 year period, 19 patients who had had open heart surgery at Michael Reese Hospital underwent reoperation for relief of tamponade 3 to 42 days after Frsrn the Division of Cardiology and Cardiac Surgery, Michael Reese Hospital and Medical Center and University of Chicago Pritzker School of Medicine, Chicago, Illinois. Manuscript received August 13, 1984; revised manuscript received November 13. 1984, accepted December 5, 1984. Address for reprints: Ivan A. D'Cruz, MD, Cardiology Division, Michael Reese Hospital and Medical Center, Lake Shore Drive at 31st Street. Chicago, Illinois 60616. © 1985 by the American College of Cardiology
posterior wall was noted, such that the width of the posterior pericardial space diminished in systole and widened abruptly in early diastole. The quantity of pericardial contents (fluid, blood or clot) evacuated surgically was smaller titan usually encountered' in patients with tamponade due to various "medical" cOnditions. Thus, unlike tamponade with other perlcardial effusions, tamponade after cardiac su~gery is due to a pericardial effusion that is smaller in volume, often loculated posteriorly and associated with certain unique two-dimensional echocardiographic features. (J Am Coli Cardiol 1985;5:1250-2)
operation. Two-dimensional echocardiography was per-' formed in II of these patients using a wide angle mechanical sector scanner (Advanced Technical Laboratories). This series of II patients comprised 7 men and 4 women, whose ages ranged from 31 to 73 years (mean 59). The original cardiac operation was coronary artery bypass grafting in eight, mitral valve replacement in two and atrial septal defect repair in one. Evidence of tamponade. Echocardiography was performed after clinical signs of tamponade had developed and usually preceded surgical relief of tamponade by less than a few hours. In all cases, after an initial postoperative period with stable signs, the following evidence for tamponade was observed: 1) decrease in systemic blood pressure, with increase in jugular venous pressure, tachycardia and respiratory distress; and 2) after removal of the pericardial contents, an immediate substantial increase in blood pressure (mean increase 45 mm Hg), with concomitant increase in pulse pressure, decrease in venous pressure and improvement in general cardiac status. A paradoxical P41se (varying from 15 to 40 mm Hg) was noted in six patients, including all four patients with a nonloculated pericardial effusion, but only two of those with a loculated posterior effusion.
Results Relief of tamponade. The pericardial contents, removed surgically, varied from 180 to 700 ml in volume, 0735-1097/85/$3.30
lACC Vol. 5, No.5
D'CRUZ ET AL. ECHOCARDJOGRAPHY IN POSTOPERATIVE TAMPONADE
May 1985:125G-2
and in appearance consisted of bloodstained pericardial fluid, unclotted recently extravasated blood, "old" dark blood or blood clots or various combinations of these. The case of a 64 year old man is worth reporting in detail. He had been on Coumadin therapy because of pulmonary embolism complicating the postoperative course after coronary bypass surgery. He was readmitted 6 weeks after his initial surgery for chest discomfort and dyspnea. Prothrombin time then was 24 seconds (control 12 seconds). The two-dimensional echocardiogram demonstrated a large loculated pericardial effusion (Fig. 1). A few hours later, the patient rapidly became hypotensive. Swan-Ganz catheterization revealed pressures (mm Hg) as follows: right atrium, mean = 15, a wave = 25, v wave = 15; right ventricle = 42115; pulmonary artery = 42120; pulmonary artery wedge, mean = 20, a wave = 20, v wave = 39. Emergency surgical drainage of the loculated pericardial effusion was promptly scheduled. In the operating room, immediately before subcostal drainage of the pericardial effusion, the pressures (mm Hg) were: central venous, 20; pulmonary artery wedge, 30; mean arterial, 60. Four hundred ml of bloody fluid were removed, and immediately thereafter pressures (mm Hg) were: central venous, 10; pulmonary artery wedge, 15; mean arterial, 95 (systolic 128, diastolic 60). These pressures remained essentially unchanged over the next 48 hours. Echocardiographic findings. A moderate to large nonloculated pericardia I effusion was noted in four patients. Pericardial fluid was visualized anterior and posterior to the heart, as well as posterior to both atria. Some abnormal pendulous cardiac motion was present, but neither extreme
ENODIASTOLE
SYSTOLE
"swinging" cardiac motion nor alternation of cardiac position was observed. Excessive inward motion (indentation) of the right atrial wall (5) was noted in two of the four patients. Phasic reciprocal changes with respiration in right and left ventricular size (1,3) could be identified in all four patients when the videotape was reviewed in slow motion or in frame by frame sequence. In the other seven patients. the pericardial fluid was loculated posteriorly behind the left ventricle. No pericardial fluid was visualized anterior to the heart, even with the patient sitting upright. Phasic respiratory changes in ventricular dimensions were not present. In these patients, the contour of the left ventricular and atrial posterior wall was abnormal: convex to the left ventricular chamber, concave toward the posterior pericardial effusion. In two patients with a loculated pericardial effusion. a strikingly unusual motion of the left ventricular posterior wall and behavior of the posterior pericardial space was observed in long-axis as well as short-axis views: the posterior pericardial space decreased in width in systole and abruptly increased in width in diastole (Fig. I). In diastole, the left ventricular posterior wall moved abruptly anteriorly; concomitantly the left ventricular dimension decreased. A decrease in left ventricular cavity width in diastole was evident in long-axis, short-axis and apical four chamber views. The systolic and diastolic phases of the cardiac cycle were identified with reference to mitral valve motion and the simultaneously recorded electrocardiogram. Such' 'paradoxical' , motion of the left ventricular posterior wall is the reverse of what is usually noted in patients with a pericardial effusion of moderate size. Systolic posterior motion of the
WID DIASTOLE
APICAl 1.0 GAXI S
(f!J. v
LV
trT
1251
Figure 1. Two-dimensional echocardiogram of a patient with postoperative pericardial effusion (EFF) showing serial frames from the same cardiac cycle in the apical long-axis view (top row), the apical four chamber view (middle row) and parasternal short-axis view (bottom row). In each row, the left frame is at enddiastole, the center frame in systole and the right frame in mid-diastole.The phases of the cardiac cycle were identified with reference to motion of the mitral valve and to the simultaneously recorded electrocardiogram. A large loculated pericardial effusion is seen posterior and posterolateral to the heart, with virtually no effusion anteriorly. Note that the pericardial effusion appears wider at mid-diastole (than during systole), and that this is associated with decreased width and altered shape of the left ventricle (LV), which becomes more concave toward the loculated pericardial effusion. LA = left atrium; PER = pericardium; RV = right ventricle.
1252
D'CRUZ ET AL. ECHOCARDIOGRAPHY IN POSTOPERATIVE TAMPONADE
left ventricular wall may be noted in association with a large pericardial effusion and "swinging" heart, but in our patients there was no cardiac swinging because the heart was tethered anteriorly by pericardial adhesions. In addition to the 11 patients requiring reoperation for tamponade. I patient developed mild tamponade due to a nonloculated pericardial effusion 3 days after coronary bypass surgery and was managed conservatively. Serial echocardiograms during the next 4 days demonstrated a gradual decrease of the pericardial effusion and regression of clinical signs of tamponade.
lACC Vol. 5, No.5 May 1985:1250-2
respiratory changes in ventricular dimensions (1,3), right ventricular narrowing (2) or abnormal motion of the right ventricular or right atrial wall (4,5). These ultrasound signs of tamponade were present in varying degree in the four patients in our series who had a nonloculated pericardial effusion, with pericardial fluid freely distributed all around both ventricles and also behind both atria. We are indebted to Karl T. Weber, MD, Director, Cardiology Division, Michael Reese Hospital for helpfully reviewing this manuscript.
References Discussion Pericardial effusion causing cardiac tamponade is not uncommon after cardiac surgery. Although it is most frequently encountered in the immediate postoperative period, Jones et al. (II) collected 43 instances of late postoperative tamponade (7 days to 3 months after cardiac surgery) reported before 1979. Loculated pericardial effusions causing tamponade. Echocardiography has been found useful in detecting a loculated posterior pericardial effusion presenting with tamponade after surgery (9-11). Seven of our patients with tamponade after surgery had a posterior loculated pericardial effusion. Postoperative loculated pericardial effusions causing tamponade by selective compression of the left atrium (12), right ventricular outflow area (13) and right atrium (14, IS) have been described. Dunlap et al. (16) presented echocardiographic and hemodynamic data indicating cardiac compression in a 25 year old man who had a posttraumatic massive organized pericardial hematoma posterior to the heart. Abnormal left ventricular wall motion. To our knowledge, the type of abnormal left ventricular posterior wall motion noted in two of our patients (Fig. I) has not been described before, although it seems present in the M-mode echocardiograms of a patient described by Jones et al. (11) (their Fig. 2). The posterior pericardial space appears to expand in early diastole, and narrow during systole, the reverse of what is usually observed in pericardial effusions. It is likely that this finding and the concave contour of the left ventricular and atrial posterior wall, noted in some of our patients with a loculated posterior pericardial effusion, is due to the high pressure in such effusions. This deformation of the left heart shape may be expected to be less prominent during systole than in diastole; this, in fact, is what was observed on two-dimensional echocardiography. Tamponade complicating various "medical" causes of pericarditis is usually caused by nonloculated pericardial effusions, and manifests echocardiographically by phasic
I. D'Cruz lA, Cohen HC, Prabhu R, Glick G. Diagnosis of cardiac tamponade by echocardiography: changes in mitral valve motion and ventricular dimensions with special reference to paradoxical pulse. Circulation 1975;52:460-6.
2. Schiller NB, Botvinick EH. Right ventricular compression as a sign of cardiac tamponade. An analysis of echocardiographic dimensions and their clinical implication. Circulation 1977;56:774-9. 3. Steele HP, Adolph Rl, Fowler NO. Echocardiographic study of cardiac tamponade. Circulation 1977;56:951-9. 4. Armstrong WF, Schilt BF, Helper nr, Dillon lE, Feigenbaum H. Diastolic collapse of the right ventricle with cardiac tamponade: an echocardiographic study. Circulation) 982;65: 1491-6. 5. Gillam LD, Guyer D, Gibson TC, King ME, Marshall 1, Weyman AE. Hydrodynamic compression of the right atrium: a new echocardiographic sign of cardiac tamponade. Circulation 1983;68:294-301. 6. Nelson RM, lenson CB, Smoot WM. Pericardial tamponade following open-heart surgery. 1 Thorac Cardiovasc Surg 1969;58:510-6. 7. Prewitt TA, Rackley CE, Wilcox BR, Scatlift JH, Young DT. Cardiac tamponade as a late complication of open-heart surgery. Am Heart J 1968;76:139-41. 8. SCOII RAP, Drew CEo Delayed pericardial effusion with tamponade after cardiac surgery. Br Heart 11973;35:1304-6. 9. Merrill W, Donahoo JS, Brawley RK, Taylor D. Late cardiac tamponade. A potentially lethal complication of open-heart surgery. J Thorac Cardiovasc Surg 1976;72:929-32. 10. Fernando HA, Friedman HS, Legam F, Sakurai H. Late cardiac tamponade following open-heart surgery. Detection by echocardiography. Ann Thorac Surg 1977;24:174-7. II. Jones MR, Vine DL, Alias M, Todd EP. Late isolated left ventricular tamponade. Clinical, hemodynamic and echocardiographic manifestations of a previously unreported postoperative complication. J Thorac Cardiovasc Surg 1979;77:142-6. 12. Yacoub MH, Cleland WP, Deal CWo Left atrial tamponade. Thorax 1966;21:205-9. 13. Hill 10, Johnson DC, Miller GE, Kwith WJ, Gerbode F. Latent mediastinal tamponade after open-heart surgery. Arch Surg 1969;19:808-14. 14. Kronzon I, Cohen ML, Winer HE. Cardiac tamponade by loculated pericardial hematoma: limitations of M-mode echocardiography. J Am Coli Cardiol 1983;3:913-5. 15. Young SC, Gregoratos G, Swain lA, Joyo CI. Delayed postoperative cardiac tamponade mimicking severe tricuspid valve stenosis. Chest 1984;85:824-6. 16. Dunlap TE, Sorkin RP, Mori KW, Popat KD. Massive organized intrapericardial hematoma mimicking constrictive pericarditis. Am Heart J 1982;104: 1373-5.