Quantitative clinical assessment of chronic anterior myocardial infarction with delayed enhancement magnetic resonance imaging and QRS scoring.

BACKGROUND: Both the regional and global myocardial extent of chronic myocardial infarction (MI) are important prognostic factors for length and quality of life and also crucial for the choice of therapy in patients with ischemic heart disease. Our aim was to develop and validate techniques for comparison between regional and global size of remote anterior MI in the left ventricle quantified with both magnetic resonance imaging (MRI) and electrocardiogram (ECG). METHODS: Delayed-enhancement (DE) MRI was used as a clinical "gold standard" for MI size to evaluate the extent of MI estimated with the commonly available standard 12-lead ECG. A method for comparing global and regional quantifications of MI with DE-MRI and ECG was developed. The Selvester QRS-scoring system was used for estimating MI size electrocardiographically. RESULTS: Twenty-five patients with chronic single anterior MI, documented with DE-MRI, were studied. The best agreement for mean % MI per regional segment of the left ventricle was found in the middle third (26% vs 27%), whereas the most significant discrepancy was found in the apex (56% vs 30%). The global MI size of the left ventricle averaged 21 +/- 9% with DE-MRI and 22% +/- 12% with ECG, with a correlation of r = 0.40 (P <.05). CONCLUSIONS: The current Selvester QRS scoring system performs well for quantifying anterior MI in the mid-regions of the left ventricle. The diagnostic performance of the Selvester QRS-scoring system for quantifying MI in the other regions, particularly the left ventricular apex, can potentially be improved, with DE-MRI as the gold standard.

Modified INOvent for delivery of inhaled nitric oxide during cardiac MRI.

BACKGROUND: The aim of this study was to assess the feasibility of delivering NO through a modified system to allow clearance of the magnetic field and thus compatibility with cardiac magnetic resonance (CMR). Nitric oxide (NO) is an inhalational, selective pulmonary vasodilator with a wide range of applications in a variety of disease states, including diseases that affect the right ventricle. Accurate assessment of dynamic changes in right ventricular function necessitates CMR; however, delivery of NO is only possible using equipment that is not magnetic resonance imaging (MRI) compatible (INOvent delivery system, Ohmeda, Inc., Madison, WI, USA). METHODS: The INOvent delivery system was modified by using 35 ft. of standard oxygen tubing to allow NO delivery through an electrical conduit and into the MRI suite. The concentrations of oxygen (O(2)), nitrogen dioxide (a harmful byproduct, NO(2)) and NO were measured in triplicate using the built-in electrochemical analyzer on the INOvent. After confirmation of safety, the system was used to administer drug to a patient x, and dynamic MRI measurements were performed. RESULTS: When the standard INOvent was set to administer 40 ppm of NO, the mean/standard deviation of gas delivered was as follows: NO: 42/0 ppm; NO(2): 0.3/0.1 ppm; and O(2): 93/0 ppm. In comparison, the gas delivery of the modified INOvent was follows: NO: 41/0 ppm; NO(2): 0.5/0 ppm; and O(2): 93.7/0.6 ppm. During administration to an index patient with severe pulmonic insufficiency (PI), a measurable reduction in PI was observed by CMR. CONCLUSIONS: Nitric oxide can be administered through 35 ft. of standard oxygen tubing without significantly affecting dose delivery. This technique has potential application in patients with right-sided structural heart disease for determination of dynamic physiological changes.