Edema is a sign of early acute myocardial infarction on post-mortem magnetic resonance imaging

Abstract

The aim of this study was to investigate if acute myocardial infarction can be detected by post-mortem cardiac magnetic resonance (PMMR) at an earlier stage than by traditional autopsy, i.e., within less than 4 h after onset of ischemia; and if so, to determine the characteristics of PMMR findings in early acute infarcts. Twenty-one ex vivo porcine hearts with acute myocardial infarction underwent T2-weighted cardiac PMMR imaging within 3 h of onset of iatrogenic ischemia. PMMR imaging findings were compared to macroscopic findings. Myocardial edema induced by ischemia and reperfusion was visible on PMMR in all cases. Typical findings of early acute ischemic injury on PMMR consist of a central zone of intermediate signal intensity bordered by a rim of increased signal intensity. Myocardial edema can be detected on cardiac PMMR within the first 3 h after the onset of ischemia in porcine hearts. The size of myocardial edema reflects the area of ischemic injury in early acute (per-acute) myocardial infarction. This study provides evidence that cardiac PMMR is able to detect acute myocardial infarcts at an earlier stage than traditional autopsy and routine histology.

Essentials of forensic post-mortem MR imaging in adults

“…The literature provides strong evidence that T 2 weighted MR images are of paramount importance in post-mortem imaging: their ability to highlight fluid accumulations makes them an ideal diagnostic tool for a wide range of pathologies, including subcutaneous haematoma, bone contusion, organ laceration, internal haemorrhage and fluid collections, ischaemic injury of the heart, brain oedema, pericardial or pleural effusion and pulmonary oedema. 6,19,23,31,[39][40][41][42][43][44] In our experience, STIR sequences are most suitable for screening purposes because they emphasize the signal from tissues with long T 2 relaxation times 45 and fluid accumulations literally flash like light bulbs when scrolling through images on STIR sequences. Thus, we refer to this phenomenon as the "forensic sentinel sign" ( Figure 6).…”

“…The extent of ischaemia-induced oedema depends heavily on the occurrence of vascular reperfusion. 42,65 Combined ischaemia/reperfusion injury results in more extensive oedema (with both intracellular and interstitial fluid accumulation) than ischaemic injury without vascular reperfusion (where fluid accumulation is often limited to the intracellular space). 65 A recent study by Ruder et al 42 revealed that oedema from ischaemia/ reperfusion injury can be detected on PMMR within 3 h after the onset of vascular occlusion.…”

“…Therefore, we would like to offer the following advice to inexperienced investigators: if oedema is visible on cardiac PMMR, ischaemic injury is the first and most likely differential diagnosis. 31,42,45,[61][62][63][64][66][67][68] If oedema is not present, but PMMR features one or several small hypointense myocardial lesions, it is reasonable to include very early ischaemic injury into the differential diagnosis. 6,31,67,68 However, these findings are often very subtle, and their interpretation depends on the subjective judgment of the investigator.…”

Postmortem imaging as a complementary tool for the investigation of cardiac death

“…Jackowski et al [57][58][59][60] demonstrated that PMMR enables the detection of myocardial infarction in situ and the estimation of infarct age based on signal behaviour and quantitative T1, T2 and proton density values, better if temperature-corrected ( Figure 2). Oedema was suggested as a sign of early myocardial infarction in ex vivo porcine hearts [61]. In 2018, Wagensveld et al [62] found that the combination of MRI with heart biopsies had high sensitivity and specificity for the detection of acute and chronic myocardial infarction at postmortem examination.…”

Adult post-mortem imaging in traumatic and cardiorespiratory death and its relation to clinical radiological imaging

“…Early work was not autopsy controlled, 75 while later articles were less optimistic, 4 but, more recently, changes on T 2 weighted images have been shown in animal models and clinical studies. [76][77][78] Clinical MRI scanning tells us that there may be more complex contrast enhancement changes that may be seen, such as the delayed myocardial enhancement occurring in regions of myocardial infarction. 79 Whole body contrast angiography is possible, 80 and there is no reason that targeted techniques cannot be translated to MRI, except for cost and time.…”