Page 449 - Textbook of Pathology, 6th Edition

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Figure 16.19 Old myocardial infarct. The infarcted area shows
ingrowth of inflammatory granulation tissue.

4. Fourth to sixth week: With further removal of necrotic
tissue, there is increase in collagenous connective tissue,
decreased vascularity and fewer pigmented macrophages, CHAPTER 16
lymphocytes and plasma cells. Thus, at the end of 6 weeks,
a contracted fibrocollagenic scar with diminished
vascularity is formed. The pigmented macrophages may
persist for a long duration in the scar, sometimes for years.
A summary of the sequence of gross and microscopic
changes in myocardial infarction of varying duration is
presented in Table 16.4. The Heart

SALVAGE IN EARLY INFARCTS AND REPERFUSION
INJURY. In vast majority of cases of acute MI, occlusive
coronary artery thrombosis has been demonstrated
superimposed on fibrofatty plaque. The ischaemic injury
to myocardium is reversible if perfusion is restored within
the first 30 minutes of onset of infarction failing which
irreversible ischaemic necrosis of myocardium sets in. The
salvage in early infarcts can be achieved by the following
interventions:
1. Institution of thrombolytic therapy with thrombolytic
agents such as streptokinase and tissue plasminogen
activator (door-to-needle time <30 minutes).
2. Percutaneous transluminal coronary angioplasty (PTCA).
3. Coronary artery stenting.
4. Coronary artery bypass surgery.
However, attempt at reperfusion is fraught with the
Figure 16.18 Sequence of light microscopic changes in myocardial risk of ischaemic reperfusion injury (Chapter 3). Further
infarction.(For details, consult the text).
myonecrosis during reperfusion occurs due to rapid influx
of calcium ions and generation of toxic oxygen free
3. Third week: Necrosed muscle fibres from larger radicals.
infarcts continue to be removed and replaced by ingrowth Grossly, the myocardial infarct following reperfusion
of newly formed collagen fibres. Pigmented macrophages injury appears haemorrhagic rather than pale.
as well as lymphocytes and plasma cells are prominent Microscopically, myofibres show contraction band necrosis
while eosinophils gradually disappear. which are transverse and thick eosinophilic bands.