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Localized pericardial tamponade: Difficult echocardiographic diagnosis of a rare complication after cardiac surgery
CASE REPORTS
Localized Pericardial Tamponade: Difficult Echocardiographic Diagnosis of a Rare Complication After Cardiac Surgery Adrian Ionescu, MRCP, (UK), Peter Wilde, MRCP, (UK), FRCR, and Karl R. Karsch, FESC, FACC, Bristol, United Kingdom
We report 2 cases of localized pericardial tamponade occurring soon after cardiac surgery, in which the diagnosis could not be made with transthoracic echocardiography. Computed tomography and transesophageal echocardiography, respectively, were
P
ericardial tamponade after cardiac surgery can be a life-threatening complication. Its diagnosis after a heart operation is difficult, often delayed, and requires a high index of suspicion.1,2 Postoperative pericardial effusions are often localized or loculated and may be extremely difficult to image by echocardiography.We report 2 cases in which large pericardial effusions causing localized compression of the right-sided heart chambers were missed initially on transthoracic echocardiography and were correctly diagnosed with computed tomography (CT) and transesophageal echocardiography, respectively. The diagnosis was confirmed at surgery in both cases.
CASE REPORTS Case 1 A 72-year-old man had elective redo aortic valve replacement. His first operation had taken place 18 years previously, and he had received a size 21 Ionescu-Shiley aortic valve, which was now degenerated,stenotic,and incompetent.The reoperation was uneventful, and the patient received a size 21 Hancock porcine valve. However, he had to be returned to the operating room 4 hours later because of bleeding and low cardiac output. Blood (2.5 L) was evacuated from the
From the Departments of Cardiology (A.I., K.R.K.), and Radiology (P.W.), Bristol Royal Infirmary, Bristol, UK. Reprint requests: Dr Adrian Ionescu, Cardiology Department, B1 Link Corridor, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK (E-mail: [email protected]). Copyright © 2001 by the American Society of Echocardiography. 0894-7317/2001/$35.00 + 0 27/4/115620 doi:10.1067/mje.2001.115620
1220
necessary, and this underlies the importance of alternative imaging modalities when this condition is suspected. A high index of suspicion is crucial for reaching the correct diagnosis. (J Am Soc Echocardiogr 2001;14:1220-3.)
right pleura, and a transesophageal echocardiogram, performed to rule out pericardial tamponade, suggested ‘underfilling /? extrinsic compression’ of the right-sided cardiac chambers. He improved hemodynamically after surgical drainage of the right pleura, and then made an uneventful recovery and was discharged home 1 week later on warfarin (which was to be continued for 3 months). One week after discharge he was readmitted feeling unwell, clammy, and short of breath. On examination, he was tachypneic, anxious, and restless. His central venous pressure was elevated at 5 cm, and the heart sounds were normal. There was no paradoxical pulse. His blood pressure was 105/65 mm Hg, and his heart rate was 124 bpm, in atrial fibrillation (of new onset). The lungs were clear, and there was no other abnormality. The chest x-ray film showed an enlarged cardiac silhouette, clear lung fields, and mild mediastinal broadening. These appearances were similar to those noted before his recent discharge from the hospital.The electrocardiogram showed atrial fibrillation and diffuse flattening of the T waves. His hemoglobin was 10.1, and his electrolytes and liver function tests were normal. His International Normalized Ratio was markedly elevated at 5.5 (target range 2.5 to 3.5). An urgent transthoracic echocardiogram was requested to rule out pericardial tamponade. The study was performed by an experienced technician and was technically very difficult, but no pericardial effusion was seen.The artificial aortic valve was noted to have a normal appearance and function, and the left ventricular function was within normal limits. Because of poor alignment from the standard apical 4-chamber view, the Doppler trace of the flow across the atrioventricular valves was not interpretable. The patient went on to have a CT scan of the chest, to rule out aortic intramural hematoma/ aortic dissection.The CT scan showed a large intrapericar-
Journal of the American Society of Echocardiography Volume 14 Number 12
A
Ionescu, Wilde, and Karsch 1221
B
C
Figure 1 A, CT section at level of heart, showing large intrapericardial mass (arrows) compressing right atrium and ventricle (asterisk). B, Transthoracic echocardiogram (modified apical 4-chamber view) demonstrating large, round structure at right atrioventricular junction (asterisk), and right ventricular collapse. C, Continuous wave Doppler trace of antegrade flow through tricuspid valve, showing high velocity signal. Marker denotes a velocity of 1 m/s.
dial mass pushing the heart to the left and almost completely obliterating the right atrium and ventricle (Figure 1, A). A repeat transthoracic echocardiogram was performed by a senior cardiac radiologist.Again, the parasternal views were unremarkable and did not show any pericardial effusion. However, in the apical 4-chamber view, it was not possible to visualize the right ventricle and atrium. With the transducer placed one intercostal space above the apex, and with inferior angulation, a large (5 × 7 cm) echogenicrounded structure was seen adjacent to the atrioventricular junction and extending along the free walls of the right ventricle and atrium (Figure 1, B), also visible from the right parasternal position, with the patient rotated to the right. The right ventricle was reduced to a slitlike space through which turbulent, high velocity blood flow was visualized with color flow mapping and continuous wave Doppler (Figure 1, C).The subcostal views were very limited and did not allow visualization of the mass. Drainage with a pigtail catheter implanted through the right parasternal approach under echocardiographic guidance was performed. Over the next 24 hours, 450 mL of blood was drained but the patient’s condition deteriorated, so he went to the operating room 36 hours after being admitted. A repeat redo sternotomy was performed, and a large amount (750 mL) of thrombus (Figure 2) was evacuated from the pericardial sack, with an immediate improvement of the blood pressure and heart rate.A bleeding point
Figure 2 Large pericardial thrombus evacuated at reoperation.
was identified at the site of the previous aortic cannulation and was sutured.The patient was transferred to the intensive therapy unit in a stable hemodynamic condition and subsequently made an uneventful recovery. Case 2 A 63-year-old man had emergency coronary artery by-pass grafting for unstable angina. He received a left internal mammary artery graft to his left anterior descending
Journal of the American Society of Echocardiography December 2001
1222 Ionescu, Wilde, and Karsch
A
B
C
Figure 3 Transesophageal echocardiograms showing large loculated pericardial effusion (asterisk) lateral to right atrium (RA) and right ventricle (RV). A, Four-chamber view showing effusion adjacent to free wall of right ventricle. B, With further flexion of probe, effusion is seen to extend to level of right atrioventricular junction. Linear adhesions are visible inside effusion (arrows). C, In this short-axis view, effusion extends almost circumferentially around base of heart.
artery, and saphenous vein grafts to his circumflex and right coronary arteries. He came off by-pass uneventfully, without any inotropic support, and was returned to the intensive therapy unit in a stable hemodynamic condition. During the first 36 hours after surgery, he drained a total of 3.2 L of blood from his pleural and pericardial drains. He received an equivalent amount of blood and remained hemodynamically stable, with a systolic blood pressure around 95 to 100 mm Hg, maintained with infusions of vasopressor drugs. He was extubated 40 hours after the operation, with minimal drainage from the chest drains and with a normal chest radiograph and transthoracic echocardiogram. On the first day after extubation, he suddenly became hypotensive and short of breath. A repeat electrocardiogram and chest radiograph were normal. A transesophageal echocardiogram was requested. This showed a large loculated pericardial effusion around the right atrium and great vessels at the base of the heart (Figure 3).The right atrium collapsed partially in diastole. The effusion extended caudally around the free wall of the right ventricle, but its width at this level was much less than at the level of the right atrium, and there was no right ventricular collapse. Pulse Doppler recordings across the mitral and tricuspid valves showed excessive respiratory variation of the flow velocities. A large right pleural effusion was also noted. The patient had emergency redo thoracotomy, and 1 L of blood under tension was evacuated from the pericardium, together with 1.5 L of blood from the right pleura. No discrete bleeding source could be identified. He made an uneventful recovery.
DISCUSSION The clinical features of cardiac tamponade were described a long time ago, but after cardiac surgery
they are often absent or mitigated. A high index of suspicion is required for the diagnosis, and echocardiography is the method of choice, but may have important limitations if only the transthoracic approach is used. In a retrospective series of 510 cardiac surgical patients Russo et al3 found tamponade (occurring on average 8 days after surgery) in 10 (2%) patients, and in 9 of them the clinical findings were atypical. Excessive anticoagulation was present in only 3 of 8 patients on anticoagulants. Similar figures were reported by Pepi et al,4 who encountered tamponade in 15 of 803 (1.9%) consecutive surgical patients. The echocardiographic features of postoperative tamponade have been studied by Chuttani et al5 in a retrospective series of 29 patients.Two thirds of the patients had a localized posterior effusion, and collapse of the right atrium or ventricle was seen in a third of the patients, respectively. Clinical findings correlated to the echocardiographic appearances: The clinical signs of tamponade were present in a much higher proportion of patients who had circumferential effusions compared with those with localized effusions. Russo et al3 noted the absence of anterior pericardial effusion (6 of 10 patients) and tethering of the anterior right ventricular wall, and found compression of the left ventricle in 4 of 10 patients. Various combinations of collapsed chambers were present in the other patients, but none had concomitant right atrial and ventricular compression. With so many atypical features, it comes as no surprise that there is often a delay in diagnosing and treating the conditions of these patients. In a retrospective study of 50 (mainly postoperative) patients, Larose et al6 found that patients presented at a mean of 6 days after the onset of symptoms, then spent on average a day before an echocardiogram was re-
Journal of the American Society of Echocardiography Volume 14 Number 12
quested, and another 1 to 2 days before drainage was achieved. In almost half of the patients, the diagnosis of tamponade was not considered initially. Right ventricular and/or atrial collapse caused by pericardial hematoma and leading to low-output syndrome was reported by Beppu et al7 in a study that used transesophageal echocardiography. They noted that patients had a prominent y wave on the right atrial pressure trace, consistent with an element of constriction. In our first patient, the pericardial hematoma was located retrosternally and slightly to the right.This is a very difficult area to examine with transthoracic echocardiography, particularly in a postoperative patient. A subcostal view may sometimes image this area, but in our experience, it is rarely feasible in the early postoperative period. In our patient, the subxyphoid area was quite tender, as there were still fresh scars from the epicardial pacing wires.As it was clinically obvious that his right atrial pressure was elevated (his jugular venous pressure was raised), we believed that imaging with a complimentary modality was more important than attempting a full noninvasive hemodynamic study. Transesophageal echocardiography was considered after the initial negative transthoracic study, but we believed that more anatomic information would become available from a CT sequence and, at that stage, the patient was still hemodynamically stable. The development of a localized pericardial effusion was facilitated by the fact that at reoperation the pericardium had been dissected off the right side of the heart but not off the left side, thus creating a virtual cavity where blood had accumulated. The sequence of events was probably postoperative intrapericardial bleeding initially, which stopped spontaneously, but then recurred with an excessively elevated INR. In the second patient, the location of the effusion predominantly around the base of the heart and retrosternally also precluded its identification with
Ionescu, Wilde, and Karsch 1223
transthoracic echocardiography.The transesophageal echocardiogram, however, was diagnostic and established unequivocally the indication for surgical reexploration. In the surgical intensive therapy unit setting, transesophageal echocardiography rather than CT imaging is the investigation of choice for unexplained hemodynamic instability. Postoperative tamponade has protean and often atypical clinical features, and echocardiography can assist the diagnosis, but only if performed by operators wholly familiar with the full spectrum of postoperative complications and echographic appearances. A very low threshold for requesting complimentary imaging studies is essential for prompt diagnosis, and the selection of the diagnostic test depends on the urgency of the clinical presentation and on the local institutional protocols.
REFERENCES 1. Fowler NO. Cardiac tamponade: a clinical or echocardiographic diagnosis? Circulation 1993;87:1738-41. 2. Tsang TS, Oh JK, Seward JB. Diagnosis and management of cardiac tamponade in the era of echocardiography. Clin Cardiol 1999;22:446-52. 3. Russo AM, O’Connor WH, Waxman HL. Atypical presentations and echocardiographic findings in patients with cardiac tamponade occurring early and late after cardiac surgery. Chest 1993;104:71-8. 4. Pepi M, Muratori M, Barbier P, Doria E, Arena V, Berti M, et al. Pericardial effusion after cardiac surgery: incidence, site, size and hemodynamic consequences. Br Heart J 1994;72: 327-31. 5. Chuttani K, Tischler MD, Pandian NG, Lee RT, Mohanty PK. Diagnosis of cardiac tamponade after cardiac surgery: relations of clinical, echocardiographic and hemodynamic signs. Am Heart J 1994;127:913-8. 6. Larose E, Ducharme A, Mercier LA, Pelletier G, Harel F, Tardiff JC. Prolonged distress and clinical deterioration before pericardial drainage in patients with cardiac tamponade. Can J Cardiol 2000;16:331-6. 7. Beppu S, Tanaka N, Nakatani S, Ikegami K, Kumon K, Miyatake K. Pericardial clot after open heart surgery: its specific localization and hemodynamics. Eur Heart J 1993;14:230-4.
Localized Pericardial Tamponade: Difficult Echocardiographic Diagnosis of a Rare Complication After Cardiac Surgery Adrian Ionescu, MRCP, (UK), Peter Wilde, MRCP, (UK), FRCR, and Karl R. Karsch, FESC, FACC, Bristol, United Kingdom
We report 2 cases of localized pericardial tamponade occurring soon after cardiac surgery, in which the diagnosis could not be made with transthoracic echocardiography. Computed tomography and transesophageal echocardiography, respectively, were
P
ericardial tamponade after cardiac surgery can be a life-threatening complication. Its diagnosis after a heart operation is difficult, often delayed, and requires a high index of suspicion.1,2 Postoperative pericardial effusions are often localized or loculated and may be extremely difficult to image by echocardiography.We report 2 cases in which large pericardial effusions causing localized compression of the right-sided heart chambers were missed initially on transthoracic echocardiography and were correctly diagnosed with computed tomography (CT) and transesophageal echocardiography, respectively. The diagnosis was confirmed at surgery in both cases.
CASE REPORTS Case 1 A 72-year-old man had elective redo aortic valve replacement. His first operation had taken place 18 years previously, and he had received a size 21 Ionescu-Shiley aortic valve, which was now degenerated,stenotic,and incompetent.The reoperation was uneventful, and the patient received a size 21 Hancock porcine valve. However, he had to be returned to the operating room 4 hours later because of bleeding and low cardiac output. Blood (2.5 L) was evacuated from the
From the Departments of Cardiology (A.I., K.R.K.), and Radiology (P.W.), Bristol Royal Infirmary, Bristol, UK. Reprint requests: Dr Adrian Ionescu, Cardiology Department, B1 Link Corridor, University Hospital of Wales, Heath Park, Cardiff CF14 4XN, UK (E-mail: [email protected]). Copyright © 2001 by the American Society of Echocardiography. 0894-7317/2001/$35.00 + 0 27/4/115620 doi:10.1067/mje.2001.115620
1220
necessary, and this underlies the importance of alternative imaging modalities when this condition is suspected. A high index of suspicion is crucial for reaching the correct diagnosis. (J Am Soc Echocardiogr 2001;14:1220-3.)
right pleura, and a transesophageal echocardiogram, performed to rule out pericardial tamponade, suggested ‘underfilling /? extrinsic compression’ of the right-sided cardiac chambers. He improved hemodynamically after surgical drainage of the right pleura, and then made an uneventful recovery and was discharged home 1 week later on warfarin (which was to be continued for 3 months). One week after discharge he was readmitted feeling unwell, clammy, and short of breath. On examination, he was tachypneic, anxious, and restless. His central venous pressure was elevated at 5 cm, and the heart sounds were normal. There was no paradoxical pulse. His blood pressure was 105/65 mm Hg, and his heart rate was 124 bpm, in atrial fibrillation (of new onset). The lungs were clear, and there was no other abnormality. The chest x-ray film showed an enlarged cardiac silhouette, clear lung fields, and mild mediastinal broadening. These appearances were similar to those noted before his recent discharge from the hospital.The electrocardiogram showed atrial fibrillation and diffuse flattening of the T waves. His hemoglobin was 10.1, and his electrolytes and liver function tests were normal. His International Normalized Ratio was markedly elevated at 5.5 (target range 2.5 to 3.5). An urgent transthoracic echocardiogram was requested to rule out pericardial tamponade. The study was performed by an experienced technician and was technically very difficult, but no pericardial effusion was seen.The artificial aortic valve was noted to have a normal appearance and function, and the left ventricular function was within normal limits. Because of poor alignment from the standard apical 4-chamber view, the Doppler trace of the flow across the atrioventricular valves was not interpretable. The patient went on to have a CT scan of the chest, to rule out aortic intramural hematoma/ aortic dissection.The CT scan showed a large intrapericar-
Journal of the American Society of Echocardiography Volume 14 Number 12
A
Ionescu, Wilde, and Karsch 1221
B
C
Figure 1 A, CT section at level of heart, showing large intrapericardial mass (arrows) compressing right atrium and ventricle (asterisk). B, Transthoracic echocardiogram (modified apical 4-chamber view) demonstrating large, round structure at right atrioventricular junction (asterisk), and right ventricular collapse. C, Continuous wave Doppler trace of antegrade flow through tricuspid valve, showing high velocity signal. Marker denotes a velocity of 1 m/s.
dial mass pushing the heart to the left and almost completely obliterating the right atrium and ventricle (Figure 1, A). A repeat transthoracic echocardiogram was performed by a senior cardiac radiologist.Again, the parasternal views were unremarkable and did not show any pericardial effusion. However, in the apical 4-chamber view, it was not possible to visualize the right ventricle and atrium. With the transducer placed one intercostal space above the apex, and with inferior angulation, a large (5 × 7 cm) echogenicrounded structure was seen adjacent to the atrioventricular junction and extending along the free walls of the right ventricle and atrium (Figure 1, B), also visible from the right parasternal position, with the patient rotated to the right. The right ventricle was reduced to a slitlike space through which turbulent, high velocity blood flow was visualized with color flow mapping and continuous wave Doppler (Figure 1, C).The subcostal views were very limited and did not allow visualization of the mass. Drainage with a pigtail catheter implanted through the right parasternal approach under echocardiographic guidance was performed. Over the next 24 hours, 450 mL of blood was drained but the patient’s condition deteriorated, so he went to the operating room 36 hours after being admitted. A repeat redo sternotomy was performed, and a large amount (750 mL) of thrombus (Figure 2) was evacuated from the pericardial sack, with an immediate improvement of the blood pressure and heart rate.A bleeding point
Figure 2 Large pericardial thrombus evacuated at reoperation.
was identified at the site of the previous aortic cannulation and was sutured.The patient was transferred to the intensive therapy unit in a stable hemodynamic condition and subsequently made an uneventful recovery. Case 2 A 63-year-old man had emergency coronary artery by-pass grafting for unstable angina. He received a left internal mammary artery graft to his left anterior descending
Journal of the American Society of Echocardiography December 2001
1222 Ionescu, Wilde, and Karsch
A
B
C
Figure 3 Transesophageal echocardiograms showing large loculated pericardial effusion (asterisk) lateral to right atrium (RA) and right ventricle (RV). A, Four-chamber view showing effusion adjacent to free wall of right ventricle. B, With further flexion of probe, effusion is seen to extend to level of right atrioventricular junction. Linear adhesions are visible inside effusion (arrows). C, In this short-axis view, effusion extends almost circumferentially around base of heart.
artery, and saphenous vein grafts to his circumflex and right coronary arteries. He came off by-pass uneventfully, without any inotropic support, and was returned to the intensive therapy unit in a stable hemodynamic condition. During the first 36 hours after surgery, he drained a total of 3.2 L of blood from his pleural and pericardial drains. He received an equivalent amount of blood and remained hemodynamically stable, with a systolic blood pressure around 95 to 100 mm Hg, maintained with infusions of vasopressor drugs. He was extubated 40 hours after the operation, with minimal drainage from the chest drains and with a normal chest radiograph and transthoracic echocardiogram. On the first day after extubation, he suddenly became hypotensive and short of breath. A repeat electrocardiogram and chest radiograph were normal. A transesophageal echocardiogram was requested. This showed a large loculated pericardial effusion around the right atrium and great vessels at the base of the heart (Figure 3).The right atrium collapsed partially in diastole. The effusion extended caudally around the free wall of the right ventricle, but its width at this level was much less than at the level of the right atrium, and there was no right ventricular collapse. Pulse Doppler recordings across the mitral and tricuspid valves showed excessive respiratory variation of the flow velocities. A large right pleural effusion was also noted. The patient had emergency redo thoracotomy, and 1 L of blood under tension was evacuated from the pericardium, together with 1.5 L of blood from the right pleura. No discrete bleeding source could be identified. He made an uneventful recovery.
DISCUSSION The clinical features of cardiac tamponade were described a long time ago, but after cardiac surgery
they are often absent or mitigated. A high index of suspicion is required for the diagnosis, and echocardiography is the method of choice, but may have important limitations if only the transthoracic approach is used. In a retrospective series of 510 cardiac surgical patients Russo et al3 found tamponade (occurring on average 8 days after surgery) in 10 (2%) patients, and in 9 of them the clinical findings were atypical. Excessive anticoagulation was present in only 3 of 8 patients on anticoagulants. Similar figures were reported by Pepi et al,4 who encountered tamponade in 15 of 803 (1.9%) consecutive surgical patients. The echocardiographic features of postoperative tamponade have been studied by Chuttani et al5 in a retrospective series of 29 patients.Two thirds of the patients had a localized posterior effusion, and collapse of the right atrium or ventricle was seen in a third of the patients, respectively. Clinical findings correlated to the echocardiographic appearances: The clinical signs of tamponade were present in a much higher proportion of patients who had circumferential effusions compared with those with localized effusions. Russo et al3 noted the absence of anterior pericardial effusion (6 of 10 patients) and tethering of the anterior right ventricular wall, and found compression of the left ventricle in 4 of 10 patients. Various combinations of collapsed chambers were present in the other patients, but none had concomitant right atrial and ventricular compression. With so many atypical features, it comes as no surprise that there is often a delay in diagnosing and treating the conditions of these patients. In a retrospective study of 50 (mainly postoperative) patients, Larose et al6 found that patients presented at a mean of 6 days after the onset of symptoms, then spent on average a day before an echocardiogram was re-
Journal of the American Society of Echocardiography Volume 14 Number 12
quested, and another 1 to 2 days before drainage was achieved. In almost half of the patients, the diagnosis of tamponade was not considered initially. Right ventricular and/or atrial collapse caused by pericardial hematoma and leading to low-output syndrome was reported by Beppu et al7 in a study that used transesophageal echocardiography. They noted that patients had a prominent y wave on the right atrial pressure trace, consistent with an element of constriction. In our first patient, the pericardial hematoma was located retrosternally and slightly to the right.This is a very difficult area to examine with transthoracic echocardiography, particularly in a postoperative patient. A subcostal view may sometimes image this area, but in our experience, it is rarely feasible in the early postoperative period. In our patient, the subxyphoid area was quite tender, as there were still fresh scars from the epicardial pacing wires.As it was clinically obvious that his right atrial pressure was elevated (his jugular venous pressure was raised), we believed that imaging with a complimentary modality was more important than attempting a full noninvasive hemodynamic study. Transesophageal echocardiography was considered after the initial negative transthoracic study, but we believed that more anatomic information would become available from a CT sequence and, at that stage, the patient was still hemodynamically stable. The development of a localized pericardial effusion was facilitated by the fact that at reoperation the pericardium had been dissected off the right side of the heart but not off the left side, thus creating a virtual cavity where blood had accumulated. The sequence of events was probably postoperative intrapericardial bleeding initially, which stopped spontaneously, but then recurred with an excessively elevated INR. In the second patient, the location of the effusion predominantly around the base of the heart and retrosternally also precluded its identification with
Ionescu, Wilde, and Karsch 1223
transthoracic echocardiography.The transesophageal echocardiogram, however, was diagnostic and established unequivocally the indication for surgical reexploration. In the surgical intensive therapy unit setting, transesophageal echocardiography rather than CT imaging is the investigation of choice for unexplained hemodynamic instability. Postoperative tamponade has protean and often atypical clinical features, and echocardiography can assist the diagnosis, but only if performed by operators wholly familiar with the full spectrum of postoperative complications and echographic appearances. A very low threshold for requesting complimentary imaging studies is essential for prompt diagnosis, and the selection of the diagnostic test depends on the urgency of the clinical presentation and on the local institutional protocols.
REFERENCES 1. Fowler NO. Cardiac tamponade: a clinical or echocardiographic diagnosis? Circulation 1993;87:1738-41. 2. Tsang TS, Oh JK, Seward JB. Diagnosis and management of cardiac tamponade in the era of echocardiography. Clin Cardiol 1999;22:446-52. 3. Russo AM, O’Connor WH, Waxman HL. Atypical presentations and echocardiographic findings in patients with cardiac tamponade occurring early and late after cardiac surgery. Chest 1993;104:71-8. 4. Pepi M, Muratori M, Barbier P, Doria E, Arena V, Berti M, et al. Pericardial effusion after cardiac surgery: incidence, site, size and hemodynamic consequences. Br Heart J 1994;72: 327-31. 5. Chuttani K, Tischler MD, Pandian NG, Lee RT, Mohanty PK. Diagnosis of cardiac tamponade after cardiac surgery: relations of clinical, echocardiographic and hemodynamic signs. Am Heart J 1994;127:913-8. 6. Larose E, Ducharme A, Mercier LA, Pelletier G, Harel F, Tardiff JC. Prolonged distress and clinical deterioration before pericardial drainage in patients with cardiac tamponade. Can J Cardiol 2000;16:331-6. 7. Beppu S, Tanaka N, Nakatani S, Ikegami K, Kumon K, Miyatake K. Pericardial clot after open heart surgery: its specific localization and hemodynamics. Eur Heart J 1993;14:230-4.