Ann Thorac Surg 2006;82:1090-1091
© 2006 The Society of Thoracic Surgeons
Case report
Raised International Normalized Ratio: An Early Warning for a Late Cardiac Tamponade?
Ammad Shah, MD, MBA*,
Albert van den Brink, MD,
Bas de Mol, MD, PhD
Academic Medical Center, Amsterdam, the Netherlands
Accepted for publication January 6, 2006.
* Address correspondence to Dr Shah, Cardiothoracic Surgery Dept, Academic Medical Center, Meibergdreef 9, Amsterdam, 1105 AZ the Netherlands (Email: a.shah{at}amc.uva.nl).
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Abstract
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Seven consecutive cases of late cardiac tamponade after valvular surgery are reported; all were postoperatively treated with acenocoumarol and 6 had an international normalized ratio peak greater than 6.0 within 3 days preceding tamponade. It is suggested that during this excessive anticoagulation state a hemorrhagic event within the pericardial space precipitates the tamponade. In addition, it is proposed that all valve patients with a postoperative international normalized ratio peak greater than 5.0 within 6 weeks postoperatively should be considered for a transthoracic echocardiogram.
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Introduction
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Late cardiac tamponade (Fig 1) remains a serious complication of open heart surgery often resulting in emergency surgical intervention with the associated morbidity, and if not performed in time means certain death. We present 7 consecutive patients with late cardiac tamponade after heart surgery during a period of just greater than 4 months. Patient histories were scrutinized in detail for any clues to the possible causes with the view that any insight could assist in the improvement of preventive strategies.
In our study, we defined late tamponade to occur after 5 days, thus suitable with respect to our average admission of 5 to 7 days before transfer to the patient's referral hospital. Studies using the same definition produced tamponade incidence data between 0.2% to 2.6% [1–3]. There were no tamponades before 5 days postoperatively in our analysis group. We conducted a retrospective review of 245 consecutive open heart operations between July and November 2005 at the Amsterdam Medical Center. This included 125 coronary artery bypass grafts, 112 valvular reconstructions, and 8 other cardiac surgeries. Tamponade was confirmed by transthoracic echocardiographic or transesophageal echocardiographic procedures, or both.
We found 8 cases of late cardiac tamponade (3.3%) ranging from 5 to 42 days (mean, 18 days), which were confirmed by transthoracic echocardiography or transesophageal echocardiography, or both, after classic presenting symptoms. All patients received Acenocoumarol (Sintrom, Novartis) postoperatively and at the time of the tamponade with a target therapeutic international normalized ratio (INR) value of less than 4.0. One patient was removed from the study because the INR values were unknown for more than 1 week prior to the tamponade. There were 4 women and 3 men, and of these, 4 were older than 70 years and 3 were younger than 55 years. Strikingly all of these patients had been subjected to valvular surgery. In 6 of the 7 cases, the postoperative pericardial drain showed minimal production and was removed within 2 days after surgery. The drain of the remaining patient was removed at 4 days. This patient then had a tamponade develop 16 days later. Six of the 7 patients had an INR peak greater than 6.0 within 3 days preceding the tamponade, and 1 patient had temporary pacemaker wires removed 24 hours earlier at an INR of 4.88. On subxiphoidal drainage, 6 of the 7 patients had hemorrhagic pericardial fluid.
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Comment
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Scientific literature defines late as anything from 3 days to 15 days postoperatively. Currently there is no agreed international definition. This not only confuses the data on incidence but also confounds the pathophysiology underlying the cause.
Ultrasonographic studies by Meurin and colleagues [4] imply the possible existence of two mechanisms involved in the development of pericardial effusion after coronary artery bypass graft surgery and valvular surgery, each having a different propensity to progress to a tamponade. He observed that persisting pericardial effusion is more common after coronary artery bypass grafting than valvular surgery beyond 15 days postoperatively, whereas tamponades that develop thereafter occur 5 times more likely after valvular surgery than after coronary artery bypass grafting surgery. A number of studies have concluded that postoperative anticoagulation is a key factor, and in these studies it has been observed that excessive INR peaks precede a significant number of tamponades [5, 6]. In addition, there is evidence that the risk of hemorrhage rises exponentially greater than an INR level of 4.0 [6].
Our study indicates a strong link between supra-therapeutic INR values and tamponade. It is suspected that at the time of an INR peak, bleeding occurs within the pericardium, which then slowly reduces when the INR decreases to a therapeutic value. The movement of the heart is likely to lead to a longer bleeding episode than that expected in static tissue, continuing even during therapeutic INR values. This could then allow the development of sufficient pericardial effusion to cause a tamponade, particularly in valvular surgery due to its more invasive nature.
Supra-therapeutic INRs may be due to (1) tamponade patients being especially difficult to anticoagulate, (2) poor INR management, or (3) dietary and drug interactions with acenocoumarol [6]. The best approach may be to better manage the INR in spite of these unstabilizing factors. In particular, valve patients must be more carefully anticoagulated, and any signs of excessive INR peaks must be further investigated. There is enough evidence to initiate prospective studies in which valve patients with such a peak are screened with transthoracic echocardiography, and the progression of any pericardial effusion that is followed. Alternative dosage sequences could also be evaluated in the same manner to find a more suitable regimen for these patients. Bearing in mind that the risk of hemorrhage increases exponentially with INRs greater than 4.0, we propose that all valve patients with an INR peak greater than 5.0 for as many as 45 days postoperatively should be considered for a transthoracic echocardiography. We suggest this course of action even when classic tamponade symptoms are absent as an atypical presentation may be missed [7].
Our preventive strategy for inter-doctor variations is simply to allocate a single individual per department to manage the INR at the place of surgery and at the referral hospital. In addition, patient education with respect to diet and drug interactions with anticoagulation therapy is highly recommended. Providing a take-home tamponade symptom checklist may alert both the patient and the patient's doctor earlier, which would buy valuable time. We believe that the link between excessive INR and tamponade has been sufficiently established to require further attention to anticoagulation in the prevention of this potentially fatal complication.
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References
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- Meurin P, Weber H, Renaud N, et al. Evolution of the postoperative pericardial effusion after day 15the problem of the late tamponade. Chest 2004;125:2182-2187.[Abstract/Free Full Text]
- Malouf JF, Alam S, Gharzeddine W, Stefadouros MA. The role of anticoagulation in the development of pericardial effusion and late tamponade after cardiac surgery Eur Heart J 1993;14:1451-1457.[Abstract/Free Full Text]
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- 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(1):71-78.[Abstract/Free Full Text]
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Abstract
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