Case Analysis

Although this patient does not fit the classical definition of sudden cardiac death (sudden collapse without symptoms, or death within one hour of symptom onset), essentially this is a sudden death case. He had acute respiratory distress of only a few hours duration. In retrospect, his complaints the day prior to admission were almost certainly related to the events that led to his death. When he presented to the hospital he had a low blood pressure (even if he was adequately treated for his longstanding hypertension, 100/64 mmHg is hypotensive), tachycardia, and tachypnea. This suggests significant acute compromise of his cardiopulmonary system. He then developed severe, acute chest pain radiating to his upper back. Together with a widened mediastinum on chest X-ray, the physicians evaluating him in the emergency department suspected an aortic dissection. A CT scan of the thorax with contrast was ordered which confirmed the diagnosis. Although this was the appropriate diagnostic modality to evaluate a suspected aortic dissection, the interpretation of the scan was inaccurate, thereby providing a false positive result. Soon thereafter, he deteriorated and developed shock and cardiac arrest. He died in a short period of time despite resuscitative measures. In retrospect, the inaccurate diagnosis of aortic dissection, and the treatment that may or may not have been instituted as a result of the diagnosis, did not play a role in his death. Before addressing the actual disease process that led to this patient's demise, it is worthwhile to address whether the suspicion of aortic dissection was reasonable.

Dissection of the aorta has multiple etiologies. One group of entities is the congenital or inherited abnormalities of the aortic connective tissue, most commonly represented by Marfan's syndrome. The latter is an autosomal dominant disease, with high penetrance, that results from a mutation in the fibrillin-1 gene on chromosome 15. Although the penetrance is high, the phenotypic features of Marfan's syndrome are variable, related to the greater than 50 different mutations of the fibrillin gene. Fibrillin is a 1015 nm microfibrillar protein component of elastic tissue. Abnormal fibrillin affects connective tissue throughout the body, thereby leading to elongated skeleton, subluxation of the lens, annuloectasia of the aortic valve ring, and fibromyxomatous cardiac valve degeneration, among other conditions. Classically, Marfan associated aortic dissection occurs in the 2nd to the 4th decades of life. In contrast, non-Marfan's dissection is a disease of unknown etiology, often associated with hypertension, and occurring most often in individuals in the through the decades. There is no known hereditary predisposition, and no mutations of connective tissue have been identified. However, it is noteworthy that aortic tissue from Marfan's syndrome and non-Marfan's dissections has an increased friability and increased ease in separating the tissue layers (e.g. split the media). This suggests that even non-Marfan's syndrome dissections are secondary to some type of connective tissue defect.

Although the patient had hypertension by history, the likelihood of a spontaneous dissection leading to his cardiovascular collapse is significantly less likely due to his age. More specifically, someone 77 years old, with recognized atherosclerotic cardiovascular disease (a myocardial infarction 10 years before admission), is virtually precluded from developing dissection. This broad statement is predicated on the fact that such a patient is almost certain to have aortic atherosclerosis; and, this condition, even if moderately severe, leads to intimal and medial plaque formation. The atherosclerotic plaque destroys the normal lamellar structure of the media, and replaces it with scar and plaque material. Intact elastic lamellae are a necessary requirement for dissection, as the dissecting channel of blood splits apart the layers comprising the media. Although localized plaque hemorrhage and focal dissection may occur in an atherosclerotic aorta, spread of the dissection is stopped when the channel of blood reaches an adjacent scarred region. In a similar way, aortitis with scarring (e.g. syphilitic aortitis) precludes dissection. Rupture of an atherosclerotic aneurysm is far more likely in a patient in his 8th decade, than a ruptured aortic dissection. Thus, on clinical and pathological grounds, the consideration of aortic dissection as a possible diagnosis in this patient should not have been high on the differential diagnosis list.

The rapid downhill course of this patient with cardiogenic shock and pulmonary edema is explained by the postmortem findings of acute coronary occlusion, acute posterolateral wall myocardial infarction, and a ruptured papillary muscle. Statistically, the two most likely causes of cardiogenic shock in this age group would be a massive myocardial infarction with extensive damage of the myocardium, and a myocardial infarction with tissue disruption (e.g. acquired ventricular septal defect or papillary muscle rupture). With tissue disruption, the infarction may be relatively small, yet have disproportionate effects on ventricular function. In the current case, that is precisely what occurred, with a rupture of the posterolateral papillary muscle. This event accounted for the acute mitral regurgitation (new holosystolic 3/6 murmur) followed by rapid development of cardiogenic shock, and respiratory distress due to pulmonary edema. It is not clear why the clinical staff considered the diagnosis of acute aortic dissection with this constellation of findings. An aortic dissection, even if it led to aortic valve insufficiency due to annular disruption, would be associated with a diastolic murmur. Furthermore, aortic dissection is only rarely associated with cardiogenic shock, and pulmonary edema. It is most often associated with sudden death due to rupture and pericardial tamponade. If it extends retrograde towards the aortic annulus, it can dissect or occlude a main coronary artery at the ostium, and under those circumstances it could cause massive myocardial injury and cardiogenic shock.

Rupture of the myocardium can affect 3 main sites: free left ventricular wall, interventricular septum, and papillary muscle. Ruptures tend to occur more frequently in patients in their 6th to 7th decades, in a background of hypertension, and often with no prior history of myocardial infarction. Ruptures of the free wall lead to rapid death with pericardial tamponade. Either the interventricular septum or papillary muscle rupture can lead to cardiogenic shock. The latter, can affect the entire papillary muscle body (the so-called 'belly'), any of the separate muscular heads (there are often as many as six separate heads), or at the myotendon junction where it can lead to disruption of a primary chorda tendineae. With complete disruption of the entire papillary muscle, massive mitral valve regurgitation and overwhelming pulmonary edema ensues rapidly, often leading to death before surgical intervention. Rupture of a single head or of a chord may permit surgical repair. In such conditions, either replacement of the entire mitral valve with prosthesis, or more recently, chordal plication or repair in order to salvage the native valve, may be attempted.

In this case, the rupture of the papillary muscle was not diagnosed, but even if it had been, it is unlikely that there would have been sufficient time to permit surgical intervention. An echocardiogram, if it had been performed rather than a CT scan, would have revealed segmental left ventricular wall motion abnormalities, and either papillary muscle dysfunction or rupture with a freely moving papillary muscle fragment in the ventricular chamber. In addition, severe mitral valve regurgitation would have been detected. Papillary muscle rupture, as is true with other forms of ventricular rupture associated with myocardial infarction, frequently occurs between the first to 4th day after infarct inception. True to form, the infarction in this case was approximately 2 days old, based on the presence of well-defined coagulative necrosis and a heavy infiltration of neutrophils.

Suggested Readings

1. Nienaber CA, Von Kodolitsch Y. Therapeutic management of patients with Marfan syndrome: focus on cardiovascular involvement. Cardiol Rev. 1999; 7:332-41.

2. Libby P, Sukhova G, Lee RT, Liao JK Molecular biology of atherosclerosis. Int J Cardiol. 1997; 62 (Suppl 2):S23-9.

3. Leopold JA, Loscalzo J. Clinical importance of understanding vascular biology Cardiol Rev. 2000; 8:115-23.

4. Samman B, Korr KS, Katz AS, Parisi AF. Pitfalls in the diagnosis and management of papillary muscle rupture: a study of four cases and review of the literature. Clin Cardiol. 1995; 18:591-6.

5. Reeder GS. Identification and treatment of complications of myocardial infarction. Mayo Clin Proc. 1995; 70:880-4.

6. Buda AJ. The role of echocardiography in the evaluation of mechanical complications of acute myocardial infarction. Circulation. 1991; 84 (3 Suppl):I109-21.

7. Prieto A, Eisenberg J, Thakur RK. Nonarrhythmic complications of acute myocardial infarction. Emerg Med Clin North Am. 2001; 19: 397-415.

8. Robinson TF, Geraci MA, Sonneblick EH, Factor SM. Coiled perimysial fibers of papillary muscle in rat heart; morphology, distribution, and changes in configuration. Circ Res 1988; 63:577-92.

Figure 4. Infarcted papillary muscle with rupture (arrow)
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