Terry D. Bauch

Age-related cardiac muscle sarcopenia: Combining experimental and mathematical modeling to identify mechanisms

Age-related skeletal muscle sarcopenia has been extensively studied and smooth muscle sarcopenia has been recently described, but age-related cardiac sarcopenia has not been previously examined. Therefore, we evaluated adult (7.5+/-0.5 months; n = 27) and senescent (31.8+/-0.4 months; n = 26) C57BL/6J mice for cardiac sarcopenia using physiological, histological, and biochemical assessments. Mice do not develop hypertension, even into senescence, which allowed us to decouple vascular effects and monitor cardiac-dependent variables. We then developed a mathematical model to describe the relationship between age-related changes in cardiac muscle structure and function. Our results showed that, compared to adult mice, senescent mice demonstrated increased left ventricular (LV) end diastolic dimension, decreased wall thickness, and decreased ejection fraction, indicating dilation and reduced contractile performance. Myocyte numbers decreased, and interstitial fibrosis was punctated but doubled in the senescent mice, indicating reparative fibrosis. Electrocardiogram analysis showed that PR interval and QRS interval increased and R amplitude decreased in the senescent mice, indicating prolonged conduction times consistent with increased fibrosis. Intracellular lipid accumulation was accompanied by a decrease in glycogen stores in the senescent mice. Mathematical simulation indicated that changes in LV dimension, collagen deposition, wall stress, and wall stiffness precede LV dysfunction. We conclude that age-related cardiac sarcopenia occurs in mice and that LV remodeling due to increased end diastolic pressure could be an underlying mechanism for age-related LV dysfunction.

Fluoroscopic localization of the femoral head as a landmark for common femoral artery cannulation

We sought to determine the reliability of frequently used landmarks for femoral arterial access in patients undergoing cardiac catheterization. The common femoral artery (CFA) is the most frequently used arterial access in cardiac catheterization. Arterial sheath placement into the CFA has been shown to decrease vascular complications. Some authors recommend locating the inferior border of the femoral head using fluoroscopy due to the relationship of the femoral head and the bifurcation of the CFA. We performed a descriptive study in a prospective design of 158 patients undergoing catheterization from the femoral approach. A femoral angiogram was performed, and the CFA bifurcation location was recorded in relation to the inguinal ligament, middle and inferior border of the femoral head, and the inguinal skin crease. The CFA bifurcation was distal to the inguinal ligament, middle femoral head, and inferior femoral head in most patients with mean distances (cm ± SD) of 7.5 ± 1.7, 2.9 ± 1.5, and 0.8 ± 1.2, respectively. The inguinal skin crease was below the bifurcation in 78% of patients (−1.8 ± 1.6 cm). The CFA overlies the femoral head in 92% of cases. The femoral head has a consistent relationship to the CFA, and localization using fluoroscopy is a useful landmark.

Rapid Correction of Hypokalemia in a Patient with an Implantable Cardioverter-Defibrillator and Recurrent Ventricular Tachycardia

We present the case of a 74-year-old man with non-ischemic dilatated cardiomyopathy and an implantable cardioverter-defibrillator presenting with a serum potassium of 2.6 mmol/L, recurrent unstable ventricular tachycardia, and multiple defibrillations. Administration of a rapid bolus of 20 mEq KCL solution via central venous access, followed by an additional total of 80 mEq (orally and intravenously [i.v.]) over the next 2 h, resulted in immediate resolution of his recurrent unstable dysrhythmia without toxic side effects. Guidelines for rapid correction of hypokalemia quote a maximum safe administration of 20 mEq i.v./h. In addition to discussing the clinical relevance and physiologic interactions of the variables leading to this patients presentation, we discuss the successful termination of his sustained recurrent ventricular dysrhythmia by rapid potassium repletion above currently recommended rates. The patient we present is representative of a growing population, given medical and technological advances over the years. Potassium boluses may be reasonable in such circumstances, particularly in patients with ICDs.

Remote digital echocardiography for the identification of cardiac valvular disease

The Pacific Island Health Care Project cares for 250-500 patients from the US-associated Pacific Islands. Unique to the Pacific Basin is a high incidence of acute rheumatic fever, a condition that not uncommonly results in valvular heart disease. Identification of patients with severe valvular heart disease may qualify them for care in the military medical system under this project. Echocardiography has become an essential diagnostic tool for the cardiologist in identifying heart valve problems. Brooke Army Medical Center (BAMC) has established a digital echocardiography network to serve the Great Plains Region. Currently, echocardiograms are digitized at remote sites, transferred to BAMC for evaluation and stored in DICOM standard format on optical disk. The digital network system provides improved care for patients, reduces patient transport costs, permits local follow-up and reduces health care costs. New digital technologies currently under evaluation at our institution will provide smaller, less costly, portable digital imaging systems and make digital echocardiography imaging networks feasible for remote health care facilities. Combining this technology with the new era of digital imaging will allow portable echoes to be used as an extension of the stethoscope. Evaluating heart function and valvular disease in a local health facility will decrease the need for transportation of the patient to a larger facility for diagnosis or follow-up evaluation.

Rest and exercise hemodynamic and metabolic findings in active duty soldiers referred for cardiac catheterization to exclude heart disease: Insights from past invasive cardiopulmonary exercise testing using multisensor high fidelity catheters

This study describes results of iCPET from the past, which used submaximal stress and multisensor high‐fidelity catheters to exclude heart disease in a unique population of young adults.