Head-to-head comparison of multiple cardiovascular magnetic resonance techniques for the detection and quantification of intramyocardial haemorrhage in patients with ST-elevation myocardial infarction

Deciphering the Enigma of Intramyocardial Hemorrhage Following Reperfusion Therapy in Acute ST-Segment Elevation Myocardial Infarction: A Comprehensive Exploration from Mechanisms to Therapeutic Strategies

Acute ST-segment elevation myocardial infarction (STEMI) is a formidable challenge in cardiovascular medicine, demanding advanced reperfusion strategies such as emergency percutaneous coronary intervention. While successful revascularization is pivotal, the persistent "no-reflow" phenomenon remains a clinical hurdle, often intertwined with microvascular dysfunction. Within this intricate scenario, the emergence of intramyocardial hemorrhage (IMH) has garnered attention as a significant contributor. This review offers a detailed exploration of the multifaceted relationship between IMH and the "no-reflow" phenomenon, delving into the mechanisms governing IMH occurrence, state-of-the-art diagnostic modalities, predictive factors, clinical implications, and the evolving landscape of preventive and therapeutic strategies. The nuanced examination aims to deepen our comprehension of IMH, providing a foundation for the identification of innovative therapeutic avenues and enhanced clinical outcomes for STEMI patients.

Myocardial infarction size as an independent predictor of intramyocardial haemorrhage in acute reperfused myocardial ischaemic rats

Background

In previous studies, haemorrhage occurred only with large infarct sizes, and studies found a moderate correlation between the extent of necrosis and haemorrhage, but the extent of infarction size in these studies was limited. This study aimed to find the correlations between intramyocardial haemorrhage (IMH), myocardial infarction (MI), and myocardial oedema (ME) from small to large sizes of MI in a 7.0-T MR scanner.

Methods

Different sizes of myocardial infarction were induced by occluding different sections of the proximal left anterior descending coronary artery (1–3 mm under the left auricle). T2*-mapping, T2-mapping and late gadolinium enhancement (LGE) sequences were performed on a 7.0 T MR system at Days 2 and 7. T2*- and T2-maps were calculated using custom-made software. All areas were expressed as a percentage of the entire myocardial tissue of the left ventricle. The rats were divided into two groups based on the T2* results and pathological findings; MI with IMH was referred to as the + IMH group, while MI without IMH was referred to as the –IMH group.

Results

The final experimental sample consisted of 25 rats in the + IMH group and 10 rats in the –IMH group. For the + IMH group on Day 2, there was a significant positive correlation between IMH size and MI size (r = 0.677, P < 0.01) and a positive correlation between IMH size and ME size (r = 0.552, P < 0.01). On Day 7, there was a significant positive correlation between IMH size and MI size (r = 0.711, P < 0.01), while no correlation was found between IMH size and ME size (r = 0.429, P = 0.097). The MI sizes of the + IMH group were larger than those of the –IMH group (P < 0.01).

Conclusions

Infarction size prior to reperfusion is a critical factor in determining IMH size in rats.

Left atrial adaptation in ischemic heart disease: insights from a cardiovascular magnetic resonance study

Left atrium (LA) plays a key role in the overall cardiac performance. However, it remains unclear how LA adapts, in terms of function and volumes, to left ventricular dysfunction in the acute and post-acute phases of myocardial infarction. LA volumes and function were evaluated in patients in the acute phase of ST-segment elevation myocardial infarction (acute-STEMI group) and in the post-acute phase after STEMI (post-acute STEMI group). Ten age and sex-matched healthy controls served as control group. In all subjects LA was assessed by a compressed-sensing cine pulse sequence and by a 3D non-model-based reconstruction. LV infarct size and microvascular obstruction were determined on late-gadolinium-enhancement data and LV myocardial oedema and myocardial haemorrhage were measured on T2-mapping data. Indexed LA maximum and minimum volumes did not differ between the acute (n = 50) and post-acute (n = 47) STEMI groups. LA active emptying fraction (LAAEF) was higher in the acute-STEMI as compared with the post-acute STEMI groups (0.63 ± 0.23 vs 0.37 ± 0.24, p < 0.0001). Conversely, LA passive emptying fraction (LAPEF) was lower in the acute-STEMI compared with post-acute-STEMI (0.34 ± 0.15 vs 0.65 ± 0.15, p < 0.0001) patients. In the acute-STEMI group, LAAEF was positively and LAPEF negatively correlated with LV myocardial tissue damage (r = 0.523 p = 0.0001; r = - 0.451 p = 0.0013). Negative and positive correlations were also found between LAAEF and LAPEF and time after STEMI (r = - 0.559 p = 0.0013 and r = 0.589 p = 0.0006, respectively). LA increases its active contractile function in the acute phase of STEMI to support LV filling. The extent (but not the type) of LV damage determines LA adaptions which normalizes over time.

T2 mapping in myocardial disease: a comprehensive review

Cardiovascular magnetic resonance (CMR) is considered the gold standard imaging modality for myocardial tissue characterization. Elevated transverse relaxation time (T2) is specific for increased myocardial water content, increased free water, and is used as an index of myocardial edema. The strengths of quantitative T2 mapping lie in the accurate characterization of myocardial edema, and the early detection of reversible myocardial disease without the use of contrast agents or ionizing radiation. Quantitative T2 mapping overcomes the limitations of T2-weighted imaging for reliable assessment of diffuse myocardial edema and can be used to diagnose, stage, and monitor myocardial injury. Strong evidence supports the clinical use of T2 mapping in acute myocardial infarction, myocarditis, heart transplant rejection, and dilated cardiomyopathy. Accumulating data support the utility of T2 mapping for the assessment of other cardiomyopathies, rheumatologic conditions with cardiac involvement, and monitoring for cancer therapy-related cardiac injury. Importantly, elevated T2 relaxation time may be the first sign of myocardial injury in many diseases and oftentimes precedes symptoms, changes in ejection fraction, and irreversible myocardial remodeling. This comprehensive review discusses the technical considerations and clinical roles of myocardial T2 mapping with an emphasis on expanding the impact of this unique, noninvasive tissue parameter.