Absence of adverse outcomes after magnetic resonance imaging early after stent placement for acute myocardial infarction: a preliminary study

Coronary imaging with cardiovascular magnetic resonance: current state of the art

Cardiovascular magnetic resonance allows noninvasive and radiation-free visualization of both the coronary arteries and veins, with the advantage of an integrated assessment of cardiac function, viability, perfusion, and anatomy. This combined approach provides valuable integrated information for patients with coronary artery disease and patients undergoing cardiac resynchronization therapy. Moreover, magnetic resonance offers the possibility of coronary vessel wall imaging, therefore assessing the anatomy and pathology of the normal and diseased coronary vessels noninvasively. Coronary magnetic resonance angiography is challenging because of cardiac and respiratory motion and the small size and tortuous path of the coronary vessels. Several technical solutions have been developed to optimize the acquisition protocol to the specific clinical question. The aims of this review are to provide an update on current technical improvements in coronary magnetic resonance angiography, including how to optimize the acquisition protocols, and to give an overview of its current clinical application.

The role of cardiac magnetic resonance in the evaluation of patients presenting with suspected or confirmed acute coronary syndrome

Cardiac magnetic resonance imaging (CMR) has an important emerging role in the evaluation and management of patients who present with symptoms concerning for acute coronary syndrome (ACS). This paper discusses the role of CMR in the emergency department setting, where CMR can aid in the early and accurate diagnosis of non-ST elevation ACS in low and intermediate risk patients. For those with confirmed myocardial infarction (MI), CMR provides comprehensive prognostic information and can readily diagnose structural complications related to MI. Furthermore, the pattern of late gadolinium enhancement (LGE) seen on CMR can help determine the etiology of cardiac injury in the subset of patients presenting with ACS who do not have obstructive coronary artery disease by angiography.

Coronary Magnetic Resonance Imaging

This article highlights the technical challenges and general imaging strategies for coronary MRI. This is followed by a review of the clinical results for the assessment of anomalous CAD, coronary artery aneurysms, native vessel integrity, and coronary artery bypass graft disease using the more commonly applied MRI methods. It concludes with a brief discussion of the advantages/disadvantages and clinical results comparing coronary MRI with multidetector CT (MDCT) coronary angiography.

Acute myocardial infarction: safety of cardiac MR imaging after percutaneous revascularization with stents

PURPOSE

To retrospectively determine the safety of cardiac magnetic resonance (MR) imaging performed early (<14 days) after coronary stent implantation in patients with acute myocardial infarction (AMI).

MATERIALS AND METHODS

This HIPPA-compliant study was approved by the institutional review board; the informed consent requirement was waived. Consecutive patients with AMI who underwent cardiac MR imaging (study group) shortly after stent implantation (median, 3 days) were compared with control subjects who did not undergo MR imaging and were matched for clinical factors and angiographic extent of coronary disease. A 1.5-T MR imager was used to evaluate cine function, perfusion, and viability. Rates of death, nonfatal myocardial infarction, or revascularization 30 days and 6 months after stent implantation were compared with chi(2) analysis.

RESULTS

The study group consisted of 66 patients (median age, 56 years; 17 women) with 97 stents, 38 (39%) of which were drug eluting. The control group included 124 patients (median age, 58 years; 23% women) with 197 stents, 21 (10.7%) of which were drug eluting. There was no significant (P = .13) difference in the combined end point of death, nonfatal myocardial infarction, or revascularization between the study (2.0% [95% confidence interval: 0.0%, 4.5%]) and control (6.5% [95% confidence interval: 1.6%, 11.3%]) groups at 30-day follow-up. The event-free survival rate at 6-month follow-up was 91% in the study group and 83.7% in the control group (P = .18). Considering the end points separately, there was no difference in the event rate at 30-day or 6-month follow-up between groups. No adverse cardiovascular events occurred in patients with drug-eluting stents who underwent MR imaging.

CONCLUSION

Cardiac MR imaging performed shortly after AMI and percutaneous revascularization with bare metal or drug-eluting stents appears safe. The risk of adverse cardiovascular events is low and similar to that in patients who do not undergo MR imaging.

Coronary magnetic resonance imaging: current state-of-the-art

Over the past decade, coronary magnetic resonance imaging has been transformed from a scientific curiosity to a clinically useful imaging tool for patients with known or suspected anomalous coronary arteries or coronary artery aneurysms and for assessment of coronary artery bypass graft patency. Coronary magnetic resonance imaging also appears to be of clinical value for assessment of native vessel integrity in selected patients, especially those patients with suspected left main/multivessel disease. Among patients referred for X-ray angiography, a normal coronary magnetic resonance imaging strongly suggests the absence of severe multivessel disease. Technical and methodological advances in motion suppression, along with increasing clinical experience will no doubt facilitate improved visualization of the distal and branch vessel.

Long-term safety of cardiac magnetic resonance imaging performed in the first few days after bare-metal stent implantation

PURPOSE

To investigate the long-term safety of cardiac magnetic resonance imaging (CMR) performed one to seven days after coronary artery stent (bare metal) implantation.

MATERIALS AND METHODS

We analyzed 119 consecutive patients with acute myocardial infarction (MI) who underwent emergency coronary stent implantation with a bare-metal stent. CMR using a 1.5T scanner was performed on 51 patients (42.9%) at a mean of 2.7+/-3.1 days after stent implantation (CMR+ group), and the remaining 68 patients (57.1%) served as controls (CMR- group). The patients were followed up to six months for major adverse cardiac events.

RESULTS

The average stent size was 3.3+/-0.5x18.4+/-6.7 mm, and 86% of the stents were made of 316L stainless steel. There were no significant differences between the CMR+ and CMR- groups in terms of infarct features, angiographic findings, or stent characteristics. Over a mean follow-up of 4.4+/-2.1 months, 12 patients (10.1%) had 16 events (13.4%). Two patients had adverse events after early MRI scan (4.3%), a rate that is lower than the event rate in the patients who did not undergo MRI (16%, P=0.04), and one of the two events was clearly not MRI related.

CONCLUSION

CMR on a 1.5T scanner can be safely performed within one to seven days after coronary bare-metal stent implantation and is not associated with an increased risk of adverse clinical cardiac outcomes. In the light of accumulating data, the guidelines by stent manufacturers should be revised.

Very early cardiac magnetic resonance imaging for quantification of myocardial tissue perfusion in patients receiving tirofiban before percutaneous coronary intervention for ST-elevation myocardial infarction

BACKGROUND

Assessment of myocardial blood flow is important for identification and monitoring of microvascular effects of glycoprotein IIb/IIIa inhibitors. Magnetic resonance imaging is a novel noninvasive method providing complementary information on myocardial blood flow and cardiac function.

METHODS AND RESULTS

Patients (n = 53) admitted within 12 (mean, 5.8) hours after onset of symptoms were randomized to tirofiban or standard therapy before primary percutaneous coronary intervention (PCI) with stenting. Myocardial blood flow was graded by measurement of corrected Thrombolysis in Myocardial Infarction frame counts and by semiquantitative analysis of signal intensity curves from first-pass contrast-enhanced magnetic resonance perfusion. Pretreatment with tirofiban proved safe and resulted in a significantly lower corrected Thrombolysis in Myocardial Infarction frame counts (21 vs 34, P = .008) indicating improved myocardial blood flow. Magnetic resonance imaging revealed higher normalized peak signal intensities (2.19 vs 1.63, P = .046) and a trend to steeper upslopes (0.79 vs 0.48, P = .1). Cardiac left ventricular wall motion analysis resulted in a significantly lower number of myocardial segments with abnormal wall thickening (6.4 vs 8.5, P = .025).

CONCLUSIONS

Pretreatment with tirofiban appears safe and improves myocardial flow after primary PCI with stenting. Magnetic resonance imaging proved useful as a complementary method for noninvasive assessment of myocardial blood flow and cardiac function in patients with ST-segment elevation myocardial infarction undergoing primary PCI.

Cardiovascular magnetic resonance imaging

Recent advancements in magnetic resonance imaging hardware and software permit the assessment of cardiovascular structure and function at rest and during exercise or pharmacology-induced cardiac stress. With these developments, knowledge of cardiovascular imaging protocols in the magnetic resonance imaging environment is critical for nursing personnel. The purpose of this article is to review information pertinent to working in a magnetic resonance imaging environment and to describe the requirements of nursing personnel performing cardiovascular magnetic resonance imaging examinations.

Detection of acutely impaired microvascular reperfusion after infarct angioplasty with magnetic resonance imaging

BACKGROUND

Despite the reopening of the infarct-related artery (IRA) with infarct angioplasty, complete microvascular reperfusion does not always ensue.

METHODS AND RESULTS

We performed cardiovascular MRI (CMR) in 20 acute myocardial infarction (AMI) patients within 24 hours of successful infarct angioplasty and 10 control patients without obstructive coronary artery disease on a clinical 1.5-T CMR scanner. Three-month follow-up CMR in AMI patients evaluated the impact of abnormal reperfusion on recovery of function. Infarction was localized by delayed contrast hyperenhancement and impaired systolic thickening. Microvascular perfusion was assessed at rest by first-pass perfusion CMR after a bolus of gadolinium-DTPA by use of the time to 50% maximum myocardial enhancement. Whereas contrast wash-in was homogeneous in control patients, AMI patients exhibited delays in the hypokinetic region subtended by the IRA compared with remote segments in 19 of 20 patients, with a mean contrast delay of 0.9+/-0.1 seconds (95% CI, 0.6 to 1.2 seconds). At follow-up, the mean recovery of systolic thickening was lower in segments with a contrast delay of 2 seconds or more (10+/-7% versus 39+/-4%, P<0.001). A contrast delay > or =2 seconds and infarction >75% transmurally were independent predictors of impaired left ventricular systolic thickening at 3 months (P=0.002 for severe contrast delay, P=0.048 for >75% for transmural infarction).

CONCLUSIONS

CMR detects impaired microvascular reperfusion in AMI patients despite successful infarct angioplasty, which when severe is associated with a lack of recovery of wall motion.

Clinical safety of magnetic resonanceimaging early after coronary artery stent placement

OBJECTIVES

Our aim was to examine the rate of adverse cardiac events in patients undergoing magnetic resonance imaging (MRI) <8 weeks after coronary stent placement.

BACKGROUND

The risk of coronary stent thrombosis from dislodgement due to MRI early after stent placement is not well defined. Manufacturers recommend postponing MRI studies until eight weeks after coronary stent placement.

METHODS

We analyzed the Mayo Clinic Rochester Percutaneous Coronary Intervention Database and examined records of 111 patients who underwent MRI <8 weeks after coronary stent placement treated with aspirin and a thienopyridine. Occurrence of death, myocardial infarction (MI), and repeat revascularization within 30 days of MRI were recorded.

RESULTS

Magnetic resonance imaging (1.5 tesla) was performed within a median of 18 days (range, 0 to 54 days) after coronary stent placement. Four noncardiac deaths occurred, and three patients had repeat revascularization procedures. Stent thrombosis did not occur (95% confidence interval, 0% to 3.3%).

CONCLUSIONS

Magnetic resonance imaging <8 weeks after coronary stent placement appears to be safe, and the risk of cardiac death or MI due to stent thrombosis is low. Postponing MRI does not appear to be necessary.

Coronary MR angiography clinical applications and potential for imaging coronary artery disease

Over the past decade, CMRA has emerged as a unique clinical imaging tool with applications in selected populations. Patients with suspected coronary artery anomalies and patients with Kawasaki disease and coronary aneurysms are among those for whom CMRA has demonstrated clinical usefulness. For assessment of patients with atherosclerotic CAD, CMRA is useful for detection of patency of bypass grafts. At centers with appropriate expertise and resources, CMRA also appears to be of value for exclusion of severe proximal multivessel CAD in selected patients. Data from multicenter trials will continue to define the clinical role of CMRA, particularly as it relates to assessment of CAD. Future developments and enhancements of CMRA promise better lumen and coronary artery wall imaging. This may become the new target in noninvasive evaluation of CAD.