1073 Short term safety and efficacy of manganese chloride cardiovascular magnetic resonance imaging in humans

Introduction

Manganese chloride (MnCl₂) rapidly releases free Mn²⁺ in the blood allowing for its active intracellular uptake by myocytes thus making it a potentially ideal candidate for perfusion and viability studies of the myocardium. However, MnCl₂ toxicity might reduce the clinical effectiveness of the substance as a contrast agent. Therefore, we designed this study to investigate for the first time in humans the safety and efficacy of a rapid infusion of MnCl₂ for cardiovascular magnetic resonance (CMR) imaging.

Methods

Fifteen normal volunteers underwent a CMR exam on a commercial 1.5 T scanner. Before the infusion, evaluation of cardiac function was performed with a short axis mid-ventricular slice being chosen for the signal intensity studies. Images of this slice were obtained using a 2D and 3D gradient-echo inversion recovery (GRE-IR) sequence, a phase-sensitive IR sequence and a single breath-hold segmented IR prepared steady-state precession acquisition for T₁ calculations. MnCl₂ was infused in three minutes at a total dose of 5 μMol/kg. Immediately after the infusion, at 15 and 30 minutes new images were obtained and cardiac function was re-evaluated.

Results

There was a significant decrease in T₁ values compared to baseline, sustained up to 30 minutes after the MnCl₂ infusion (Table 1). The 2D GRE-IR sequence showed the greatest relative increase in signal intensity compared to the other sequences (Figure 1). There was a slight increase in systolic pressure and heart rate after three and four minutes of the infusion with normalization of these parameters thereafter. Patients showed good tolerance to MnCl₂ with no major adverse events, despite all patients reporting transient facial flush.

Figure 1

2D GRE-IR image at pre-injection (A), 0 minutes after (B), 15 minutes (C) and 30 minutes (D).

Table 1

Conclusion

In the short term, MnCl₂ appears safe for human use. It effectively decreases myocardium T₁, maintaining this effect for a relatively long period of time and allowing for the development of new imaging strategies in CMR.