Prevalence and variability in reporting of clinically actionable incidental findings on attenuation-correction CT scans in a veteran population.

BACKGROUND: Myocardial perfusion imaging (MPI) often employs attenuation-correction computed tomography (CTAC) to reduce attenuation artifacts and improve specificity. While there is no specific guideline on how they should be reported, incidental noncardiac findings identified on these scans may be clinically significant. The prevalence of these findings in veterans is not currently known. In addition, variability in reporting these findings may depend on the interpreting physician's specialty. METHODS: To guide future decision-making, CTACs in veterans referred for MPI were prospectively evaluated in a quality-control project for a set of prespecified actionable incidental findings by cardiologists and a radiologist. RESULTS: On the 771 scans performed over eight months, 285 incidental noncardiac findings were identified by the interpreting cardiologists and 378 were identified by the interpreting radiologist. Pulmonary nodules were the most common occurring in 20% of studies read by the radiologist. Interreader agreements between cardiologists and the radiologist were poor for pulmonary nodules ≥ 10 mm and hiatal hernias; fair for pulmonary nodules < 10 mm, extracardiac masses, and aortic aneurysms; and moderate for pleural plaques. CONCLUSION: Incidental noncardiac findings on CTACs are common in our veteran population. Overall interobserver agreement in identifying these findings between cardiologists and radiologists is fair. Specific guidelines are needed on how CTACs should be read and reported.

CaMKII in the cardiovascular system: sensing redox states.

The multifunctional Ca(2+)- and calmodulin-dependent protein kinase II (CaMKII) is now recognized to play a central role in pathological events in the cardiovascular system. CaMKII has diverse downstream targets that promote vascular disease, heart failure, and arrhythmias, so improved understanding of CaMKII signaling has the potential to lead to new therapies for cardiovascular disease. CaMKII is a multimeric serine-threonine kinase that is initially activated by binding calcified calmodulin (Ca(2+)/CaM). Under conditions of sustained exposure to elevated Ca(2+)/CaM, CaMKII transitions into a Ca(2+)/CaM-autonomous enzyme by two distinct but parallel processes. Autophosphorylation of threonine-287 in the CaMKII regulatory domain "traps" CaMKII into an open configuration even after Ca(2+)/CaM unbinding. More recently, our group identified a pair of methionines (281/282) in the CaMKII regulatory domain that undergo a partially reversible oxidation which, like autophosphorylation, prevents CaMKII from inactivating after Ca(2+)/CaM unbinding. Here we review roles of CaMKII in cardiovascular disease with an eye to understanding how CaMKII may act as a transduction signal to connect pro-oxidant conditions into specific downstream pathological effects that are relevant to rare and common forms of cardiovascular disease.

CaMKII determines mitochondrial stress responses in heart.

Myocardial cell death is initiated by excessive mitochondrial Ca(2+) entry causing Ca(2+) overload, mitochondrial permeability transition pore (mPTP) opening and dissipation of the mitochondrial inner membrane potential (ΔΨm). However, the signalling pathways that control mitochondrial Ca(2+) entry through the inner membrane mitochondrial Ca(2+) uniporter (MCU) are not known. The multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is activated in ischaemia reperfusion, myocardial infarction and neurohumoral injury, common causes of myocardial death and heart failure; these findings suggest that CaMKII could couple disease stress to mitochondrial injury. Here we show that CaMKII promotes mPTP opening and myocardial death by increasing MCU current (I(MCU)). Mitochondrial-targeted CaMKII inhibitory protein or cyclosporin A, an mPTP antagonist with clinical efficacy in ischaemia reperfusion injury, equivalently prevent mPTP opening, ΔΨm deterioration and diminish mitochondrial disruption and programmed cell death in response to ischaemia reperfusion injury. Mice with myocardial and mitochondrial-targeted CaMKII inhibition have reduced I(MCU) and are resistant to ischaemia reperfusion injury, myocardial infarction and neurohumoral injury, suggesting that pathological actions of CaMKII are substantially mediated by increasing I(MCU). Our findings identify CaMKII activity as a central mechanism for mitochondrial Ca(2+) entry in myocardial cell death, and indicate that mitochondrial-targeted CaMKII inhibition could prevent or reduce myocardial death and heart failure in response to common experimental forms of pathophysiological stress.

Aldosterone and cardiovascular disease: the heart of the matter.

Aldosterone contributes to the endocrine basis of heart failure, and studies on cardiac aldosterone signaling have reinforced its value as a therapeutic target. Recent focus has shifted to new roles of aldosterone that appear to depend on coexisting pathologic stimuli, cell type, and disease etiology. This review evaluates recent advances in mechanisms underlying aldosterone-induced cardiac disease and highlights the interplay between aldosterone and Ca(2+)/calmodulin dependent protein kinase II, whose hyperactivity during heart failure contributes to disease progression. Increasing evidence implicates aldosterone in diastolic dysfunction, and there is a need to develop more targeted therapeutics such as aldosterone synthase inhibitors and molecularly specific antioxidants. Despite accumulating knowledge, many questions still persist and will likely dictate areas of future research.

Oxidation of CaMKII determines the cardiotoxic effects of aldosterone.

Excessive activation of the ß-adrenergic, angiotensin II (Ang II) and aldosterone signaling pathways promotes mortality after myocardial infarction, and antagonists targeting these pathways are core therapies for treating this condition. Catecholamines and Ang II activate the multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), the inhibition of which prevents isoproterenol-mediated and Ang II-mediated cardiomyopathy. Here we show that aldosterone exerts direct toxic actions on myocardium by oxidative activation of CaMKII, causing cardiac rupture and increased mortality in mice after myocardial infarction. Aldosterone induces CaMKII oxidation by recruiting NADPH oxidase, and this oxidized and activated CaMKII promotes matrix metalloproteinase 9 (MMP9) expression in cardiomyocytes. Myocardial CaMKII inhibition, overexpression of methionine sulfoxide reductase A (an enzyme that reduces oxidized CaMKII) or NADPH oxidase deficiency prevented aldosterone-enhanced cardiac rupture after myocardial infarction. These findings show that oxidized myocardial CaMKII mediates the cardiotoxic effects of aldosterone on the cardiac matrix and establish CaMKII as a nodal signal for the neurohumoral pathways associated with poor outcomes after myocardial infarction.

Oxidized CaMKII causes cardiac sinus node dysfunction in mice.

Sinus node dysfunction (SND) is a major public health problem that is associated with sudden cardiac death and requires surgical implantation of artificial pacemakers. However, little is known about the molecular and cellular mechanisms that cause SND. Most SND occurs in the setting of heart failure and hypertension, conditions that are marked by elevated circulating angiotensin II (Ang II) and increased oxidant stress. Here, we show that oxidized calmodulin kinase II (ox-CaMKII) is a biomarker for SND in patients and dogs and a disease determinant in mice. In wild-type mice, Ang II infusion caused sinoatrial nodal (SAN) cell oxidation by activating NADPH oxidase, leading to increased ox-CaMKII, SAN cell apoptosis, and SND. p47-/- mice lacking functional NADPH oxidase and mice with myocardial or SAN-targeted CaMKII inhibition were highly resistant to SAN apoptosis and SND, suggesting that ox-CaMKII-triggered SAN cell death contributed to SND. We developed a computational model of the sinoatrial node that showed that a loss of SAN cells below a critical threshold caused SND by preventing normal impulse formation and propagation. These data provide novel molecular and mechanistic information to understand SND and suggest that targeted CaMKII inhibition may be useful for preventing SND in high-risk patients.