728-1 Determination of Stenosis Length by Magnetic Resonance Coronary Angiography

Magnetic resonance coronary angiography (MRA) can identify significant stenoses (>50%) as regions with reduced signal intensity due to disturbed intraluminal flow. To determine whether MRA stenosis length reflects true lesion length by x-ray angiography (XA). 12 patients (10 male and 2 female: age 65±8 years) underwent both MRA and XA with an average of 2.1±1.7 days between procedures. MRA was performed with the patient prone on an elliptical spine coil using a fat suppressed. TurboFlash, breath hold, segmented k-space sequence during late diastole. MRA defects were quantified off-line by manual tracing of digital images. XA stenoses were analyzed from 35 mm cine films using an electronic caliper which reported defect length, stenosis diameter and area. Matched MRA-XA stenoses included 5 in the left anterior descending (LAD), 8 right coronary artery (RCA) and 2 left circumflex (LCX). MRA and XA results were highly correlated (r=0.96). MRA reported a slightly longer stenoses length 9.65±2.0 mm versus 8.32±2.1 mm for XA (p<0.05 paired t-test). The ratio (MRA stenosis length/XA stenosis length) was not dependent on stenosis severity, absolute stenosis lumen diameter or area (MANOVA). Thus, in addition to detecting the presence of coronary lesions. MRA allows quantification of stenosis length

Reduced Sympathetic Innervation Underlies Adjacent Noninfarcted Region Dysfunction During Left Ventricular Remodeling

AbstractObjectives. We examined the association of sympathetic denervation and reduced blood flow with mechanical dysfunction in adjacent noninfarcted regions late after myocardial infarction (MI).Background. Using a well characterized ovine model of left ventricular (LV) remodeling after transmural anteroapical MI, we previously showed that histologically normal adjacent noninfarcted regions demonstrate mechanical dysfunction.Methods. Ten sheep underwent coronary ligation. Magnetic resonance imaging was performed before and 8 weeks after infarction for measurement of LV mass, volumes, ejection fraction and regional intramyocardial circumferential shortening (%S). Iodine-123 metaiodobenzylguanidine (I-123 MIBG) and fluorescent microspheres before and after administration of adenosine were infused before death for measurement of sympathetic innervation, blood flow and blood flow reserve from matched postmortem regions.Results. From baseline to 8 weeks after infarction, LV end-diastolic volume increased from (mean ± SD) 1.5 ± 0.3 to 2.6 ± 0.5 ml/kg (p < 0.001), and LV mass increased from 2.0 ± 0.3 to 2.6 ± 0.5 g/kg (p = 0.001). Regionally, the decline in subendocardial %S was greater in adjacent (19 ± 5% to 8 ± 5%) than in remote noninfarcted regions (20 ± 6% to 19 ± 6%, p < 0.002). No difference in regional blood flow or blood flow reserve was found between adjacent and remote regions, whereas I-123 MIBG uptake was lower in adjacent than in remote myocardium (1.09 ± 0.30 vs. 1.31 ± 0.40 nmol/g, p < 0.003). Topographically, from apex to base at 8 weeks after infarction, %S correlated closely with I-123 MIBG uptake (r = 0.93, p = 0.003).Conclusions. In mechanically dysfunctional noninfarcted regions adjacent to chronic transmural myocardial infarction in the remodeled left ventricle, blood flow and blood flow reserve are preserved, yet sympathetic innervation is reduced. Chronic sympathetic denervation in adjacent noninfarcted regions, in association with regional mechanical dysfunction, may contribute to LV remodeling after infarction

Contractile reserve and contrast uptake pattern by magnetic resonance imaging and functional recovery after reperfused myocardial infarction

AbstractOBJECTIVESWe hypothesized that contrast-enhanced and dobutamine tagged magnetic resonance imaging (MRI) could investigate microvascular integrity and contractile reserve of reperfused myocardial infarction (MI) in one examination.BACKGROUNDIn reperfused MI, microvascular integrity and contractile reserve are important determinants of functional recovery.METHODSTwenty-three patients with a reperfused first MI were studied. On day 3 ± 1 after MI, patients underwent tagged MRI at baseline and during infusion of 5 and 10 μg/kg/min of dobutamine followed by contrast-enhanced MRI (first pass and delayed imaging) after a bolus infusion of gadolinium-diethylenetriaminepenta-acetic acid. Tagged MRI was performed 9 ± 1 weeks later (follow-up). Eighty-four transmural regions with hyperenhancement on delayed contrast-enhanced images were defined as COMB (first pass hypoenhancement) or HYPER (normal first pass signal enhancement). Percent circumferential segment shortening was measured within the subendocardium and subepicardum of each region of HYPER or COMB at baseline, peak dobutamine and follow-up.RESULTSShortening improved in COMB regions from 4 ± 1% at baseline to 10 ± 1% at peak dobutamine and 10 ± 1% at follow-up, respectively (p < 0.0003 vs. baseline for both). The HYPER regions likewise improved from 10 ± 1% at baseline to 16 ± 1% and 17 ± 1%, respectively (p < 0.0004 vs. baseline for both). Function within COMB regions was less than that of HYPER at baseline, peak dobutamine and follow-up (p < 0.0003 for all).CONCLUSIONSDobutamine magnetic resonance tagging and contrast enhanced MRI are complementary in assessing functional recovery after reperfused MI. Regions of delayed contrast hyperenhancement demonstrate both contractile reserve and late functional recovery. However, if these regions demonstrate first pass contrast hypoenhancement, they are associated with greater myocardial damage

Global human influence maps reveal clear opportunities in conserving Earth's remaining intact terrestrial ecosystems

Leading up to the 2020 Convention on Biological Diversity there is momentum around setting bold conservation targets. Yet it remains unclear how much of Earth's land area remains without significant human influence and where this land is located. We compare four recent global maps of human influences across Earth's land, Anthromes, Global Human Modification, Human Footprint, and Low Impact Areas, to answer these questions. Despite using various methodologies and data, these different spatial assessments independently estimate similar percentages of the Earth's terrestrial surface as having very low (20-34%) and low (48-56%) human influence. Three out of four spatial assessments agree on 46% of the non-permanent ice- or snow-covered land as having low human influence. However, much of the very low and low influence portions of the planet are comprised of cold (e.g., boreal forests, montane grasslands and tundra) or arid (e.g., deserts) landscapes. Only four biomes (boreal forests, deserts, temperate coniferous forests and tundra) have a majority of datasets agreeing that at least half of their area has very low human influence. More concerning, <1% of temperate grasslands, tropical coniferous forests and tropical dry forests have very low human influence across most datasets, and tropical grasslands, mangroves and montane grasslands also have <1% land identified as very low influence across all datasets. These findings suggest that about half of Earth's terrestrial surface has relatively low human influence and offers opportunities for proactive conservation actions to retain the last intact ecosystems on the planet. However, though the relative abundance of ecosystem areas with low human influence varies widely by biome, conserving these last intact areas should be a high priority before they are completely lost.See Methods in publication