Convalescent stage coronary flow reserve and late myocardial morphologic outcomes in patients with first anterior acute myocardial infarction

Coronary microcirculatory dysfunction is associated with left ventricular dysfunction during follow-up after STEMI

BACKGROUND

Coronary microvascular resistance is increased after primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI), which may be related in part to changed left ventricular (LV) dynamics. Therefore we studied the coronary microcirculation in relation to systolic and diastolic LV function after STEMI.

METHODS

The study cohort consisted of 12 consecutive patients, all treated with primary PCI for a first anterior wall STEMI. At 4 months, we assessed pressure-volume loops. Subsequently, we measured intracoronary pressure and flow velocity and calculated coronary microvascular resistance. Infarct size and LV mass were assessed using magnetic resonance imaging.

RESULTS

Patients with an impaired systolic LV function due to a larger myocardial infarction showed a higher baseline average peak flow velocity (APV) than the other patients (26 ± 7 versus 17 ± 5 cm/s, p = 0.003, respectively), and showed an impaired variable microvascular resistance index (2.1 ± 1.0 versus 4.1 ± 1.3 mmHg cm(-1)∙s(-1), p = 0.003, respectively). Impaired diastolic relaxation time was inversely correlated with hyperaemic APV (r = -0.56, p = 0.003) and positively correlated with hyperaemic microvascular resistance (r = 0.48, p = 0.01). LV dilatation was associated with a reduced variable microvascular resistance index (r = 0.78, p = 0.006).

CONCLUSION

A larger anterior myocardial infarction results in impaired LV performance associated with reduced coronary microvascular resistance variability, in particular due to higher coronary blood flow at baseline in these compromised left ventricles.

Estimation of infarct size using transthoracic Doppler echocardiographic measurement of coronary flow reserve in infarct related and reference coronary artery

BACKGROUND

Patients in chronic phase of myocardial infarction (MI) have decreased coronary flow reserve (CFR) in infarct related artery (IRA) that is proportional to the extent of microvascular/myocardial damage. We proposed a novel model for the assessment of microvascular damage and infarct size using Doppler echocardiography evaluation of CFRs of the IRA (LAD) and reference artery (RCA).

METHODS

Our study included 34 consecutive patients (28 men, mean age 50 ± 11 years) with first anterior STEMI and single vessel disease successfully treated with primary PCI. All patients underwent SPECT MPI for the assessment of infarct size (expressed as a percentage of myocardium with fixed perfusion abnormalities) and CFR evaluation of LAD and RCA. CFR derived percentage of microvascular damage (CFR PMD) was calculated as: CFR PMD=(CFR RCA-CFR LAD)/(CFR RCA-1)×100 (%).

RESULTS

CFR PMD correlated significantly with all parameters evaluating the severity of myocardial damage including: peak CK activity (r=0.632, p<0.001), WMSI (r=0.857, p<0.001), ejection fraction (r=-0.820, p<0.001), left ventricular end diastolic (r=0.757, p<0.001) and end systolic volume (r=0.794, p<0.001). Most importantly, CFR PMD (22 ± 17%) correlated significantly with infarct size by SPECT MPI (21 ± 17%) (r=0.874, p<0.001).

CONCLUSIONS

CFR PMD derived from the proposed model was significantly related to echocardiographic and enzymatic parameters of infarct size, as well as to myocardial damage assessed by SPECT MPI in patients with successfully reperfused first anterior STEMI.

Adipose stromal vascular fraction cell construct sustains coronary microvascular function after acute myocardial infarction

A three-dimensional tissue construct was created using adipose-derived stromal vascular fraction (SVF) cells and evaluated as a microvascular protection treatment in a myocardial infarction (MI) model. This study evaluated coronary blood flow (BF) and global left ventricular function after MI with and without the SVF construct. Fischer-344 rats were separated into four groups: sham operation (sham), MI, MI Vicryl patch (no cells), and MI SVF construct (MI SVF). SVF cells were labeled with green fluorescent protein (GFP). Immediately postinfarct, constructs were implanted onto the epicardium at the site of ischemia. Four weeks postsurgery, the coronary BF reserve was significantly decreased by 67% in the MI group and 75% in the MI Vicryl group compared with the sham group. The coronary BF reserve of the sham and MI SVF groups in the area at risk was not significantly different (sham group: 83 ± 22% and MI SVF group: 57 ± 22%). Griffonia simplicifolia I and GFP-positive SVF immunostaining revealed engrafted SVF cells around microvessels in the infarct region 4 wk postimplant. Overall heart function, specifically ejection fraction, was significantly greater in MI SVF hearts compared with MI and MI Vicryl hearts (MI SVF: 66 ± 4%, MI: 37 ± 8%, and MI Vicryl: 29 ± 6%). In conclusion, adipose-derived SVF cells can be used to construct a novel therapeutic modality for treating microvascular instability and ischemia through implantation on the epicardial surface of the heart. The SVF construct implanted immediately after MI not only maintains heart function but also sustains microvascular perfusion and function in the infarct area by sustaining the coronary BF reserve.

Effect of human peripheral monocyte subsets on coronary flow reserve in infarct-related artery in patients with primary anterior acute myocardial infarction

1. In the present study, we investigated the relationships between relative levels of specific peripheral monocyte subsets and coronary flow velocity reserve (CFVR) during the subacute phase in patients with acute myocardial infarction (AMI). 2. The study was performed on 29 patients with primary anterior AMI who had been successfully treated using primary percutaneous coronary intervention. Two monocyte subsets (CD14(+)CD16(-) and CD14(+)CD16(+)) were measured by flow cytometry. Transthoracic Doppler echocardiography was used to measure CFVR on Days 4 and 7 after the onset of AMI onset. We defined DeltaCFVR as the difference in CFVR values between Days 4 and 7. The extent of myocardial salvage on Day 7 after AMI was evaluated by cardiovascular magnetic resonance (CMR) imaging as the difference between the area of myocardium at risk and the area of necrotic myocardium. 3. There was a significant negative correlation between DeltaCFVR and peak CD14(+)CD16(-) monocyte counts in AMI patients, whereas no significant association was found between CD14(+)CD16(+) monocyte counts and DeltaCFVR. There was a significant positive correlation between DeltaCFVR and the extent of myocardial salvage. 4. In conclusion, peak levels of CD14(+)CD16(-) monocytes following primary anterior AMI were closely related to the extent of microvascular injury.

Novel Doppler Technique to Assess Systemic Vascular Resistance The Snuffbox Technique

BACKGROUND

To explore an alternative to the systemic vascular resistance index (SVRI) for monitoring peripheral circulation in patients in the intensive care unit (ICU), the resistive index (RI) in the upper extremity arteries was measured by using surface Doppler ultrasound.

METHODS AND RESULTS

The correlation between RI and vascular resistance was assessed in vitro using a vessel phantom in a Donovan-type mock circulation system. In addition, 15 ICU patients who had undergone open-heart surgery were studied. Mean arterial pressure, central venous pressure and cardiac output were measured 30 times at 10 min intervals after patients returned to the ICU following surgery, and the SVRI was calculated from these parameters. At the same time points, 3 parts of the upper extremity arteries (brachial artery in the cubital fossa (BA), radial artery at the wrist (RA), and radial artery at the anatomical snuffbox (SB)) were scanned by Doppler ultrasound, and the resistance index (RI) for each artery region was calculated. In vitro, RI increased with higher vascular resistance, exhibiting a significant correlation (r = 0.982, p < 0.0001). In vivo, the average incidence angles at the BA and RA were larger than 60 degrees , while that at the SB was only 11.5+/-10.8 degrees. The overall correlation between SVRI and RI for all patients was not significant for the BA or RA, but was significant for the SB (p < 0.0001). In individual patients, the correlation of SVRI with RI at the BA or RA was significant in 3 patients only, whereas significant correlation for the SB was observed in all patients. Doppler waveform analysis at the SB revealed diastolic flow reversal with increased SVRI.

CONCLUSIONS

Measurement at the SB provides an ideal ultrasound incidence angle for the measurement of blood flow velocity. Hence, RI measured in this way may serve as an indicator of peripheral vascular resistance, and may be effective for the evaluation of peripheral circulatory disturbance.