Elucidation of a tripartite mechanism underlying the improvement in cardiac tolerance to ischemia by coenzyme Q10 pretreatment

Coenzyme Q10, which is involved in mitochondrial adenosine triphosphate production, is also a powerful antioxidant. We hypothesize that coenzyme Q10 pretreatment protects myocardium from ischemia reperfusion injury both by its ability to increase aerobic energy production and by protecting creatine kinase from oxidative inactivation during reperfusion. Isolated hearts (six per group) from rats pretreated with either coenzyme Q10, 20 mg/kg intramuscularly and 10 mg/kg intraperitoneally (treatment) or vehicle only (control) 24 and 2 hours before the experiment were subjected to 15 minutes of equilibration, 25 minutes of ischemia, and 40 minutes of reperfusion. Developed pressure, contractility, compliance, myocardial oxygen consumption, and myocardial aerobic efficiency were measured. Phosphorus 31 nuclear magnetic resonance (31P-NMR) spectroscopy was used to determine adenosine triphosphate and phosphocreatine concentrations as a percentage of a methylene diphosphonic acid standard. Hearts were assayed for myocardial coenzyme Q10 and myocardial creatine kinase activity at end equilibration and at reperfusion. Treated hearts showed higher myocardial coenzyme Q10 levels (133 +/- 5 micrograms/gm ventricle versus 117 +/- 4 micrograms/gm ventricle, p < 0.05). Developed pressure at end reperfusion was 62% +/- 2% of equilibration in treatment group versus 37% +/- 2% in control group, p < 0.005. Preischemic myocardial aerobic efficiency was preserved during reperfusion in treatment group (0.84 +/- 0.08 mm Hg/(microliter O2/min/gm ventricle) vs 1.00 +/- 0.08 mm Hg/(microliter O2/min/gm ventricle) at equilibration, p = not significant), whereas in the control group it fell to 0.62 +/- 0.07 mm Hg/(microliter O2/min/gm ventricle, p < 0.05 vs equilibration and vs the treatment group at reperfusion. Treated hearts showed higher adenosine triphosphate and phosphocreatine levels during both equilibration (adenosine triphosphate 49% +/- 2% for the treatment group vs 33% +/- 3% in the control group, p < 0.005; phosphocreatine 49% +/- 3% in the treatment group vs 35% +/- 3% in the control group, p < 0.005) and reperfusion (adenosine triphosphate 18% +/- 3% in the treatment group vs 11% +/- 2% in the control group, CTRL p < 0.05; phosphocreatine 45% +/- 2% in the treatment group vs 23% +/- 3% in the control group, p < 0.005). Creatine kinase activity in treated hearts at end reperfusion was 74% +/- 3% of equilibration activity vs 65% +/- 2% in the control group, p < 0.05). Coenzyme Q10 pretreatment improves myocardial function after ischemia and reperfusion. This results from a tripartite effect: (1) higher concentration of adenosine triphosphate and phosphocreatine, initially and during reperfusion, (2) improved myocardial aerobic efficiency during reperfusion, and (3) protection of creatine kinase from oxidative inactivation during reperfusion.

The sternalis muscle: an unusual normal finding seen on mammography

OBJECTIVE

We studied the appearance of the sternalis muscle on mammography and on CT and MR imaging. To our knowledge, this is the first description of this normal anatomic variant. An approach is provided that permits differentiation of the sternalis from significant pathology.

SUBJECTS AND METHODS

Between January 1992 and December 1994, four women of an estimated 32,000 who had mammograms at the Massachusetts General Hospital had an unusual, irregular structure visible medially on the craniocaudal projection that posed a diagnostic dilemma. The records and imaging studies of these women and two others from the Deaconess Hospital breast imaging program were reviewed to determine the etiology of the findings seen by mammography and to establish a diagnostic approach.

RESULTS

Surgery in one patient and cross-sectional imaging in the other five established that the structure was the sternalis muscle. Although it may be bilateral, the sternalis muscle was visible only unilaterally on the mammograms of these six women. The appearance of the muscle ranged from an irregularly rounded density at the sternal edge of the film to flame-shaped and almost completely surrounded by fat. CT and MR imaging are diagnostic when they show the longitudinal extent of the muscle, which lies anterior to the medial margin of the pectoralis major muscle.

CONCLUSION

The sternalis muscle is an unusual variant of the chest wall musculature. It may be visible as a rounded or irregular density on the craniocaudal mammogram along the sternal edge of the film. With improved mammographic positioning it will be seen more frequently. The muscle has a variety of appearances that should be familiar to the radiologist to avoid confusion with a malignant lesion. The etiology can be confirmed and cancer excluded by CT or MR imaging.

Nitric oxide as a positive inotropic agent in isolated rat hearts

The purpose of this study was to examine the inotropic effects of nitroprusside (NP), a direct nitric oxide (NO) donor, in isolated rat hearts. Langendorff-perfused hearts (n = 5), paced at 6 Hz, were subjected to 15 min of equilibration (EQ) followed by infusion of NP, producing a coronary artery concentration of 1 x 10(-5) M. Coronary flow, left ventricular developed pressure (DP), end-diastolic pressure, and contractility and compliance (+/- dP/dt) were monitored throughout the experiment by a computerized data acquisition system. Myocardial oxygen consumption (MVO2) was measured at the end of EQ and after 2 1/2 min of NP infusion. Myocardial efficiency was calculated as the quotient of DP divided by MVO2. Values are expressed as the mean +/- SEM. Paired t tests were used to calculate statistical significance. Values for parameters monitored at end EQ and at 2 1/2 min NP infusion showed that there was a 93% increase in coronary flow, 18, 17, and 16% increases in developed pressure, contractility, and compliance, respectively, no significant change in end-diastolic pressure, a 49% increase in myocardial oxygen consumption, and a 21% decline in myocardial efficiency (P < 0.05 for all differences). We conclude that in the isolated rat heart, NO behaves as a positive inotrope.

The cumulative nature of pyruvate's dual mechanism for myocardial protection

Pyruvate (PYR) supplementation protects myocardium from ischemia reperfusion injury. This study was designed to characterize and quantify the mechanism underlying this protection: specifically whether this ability resides in PYR's metabolic effect or in its antioxidant effect. Isolated perfused rat hearts (n = 6/group) were subjected to 15 min of equilibration (EQ), 25 min of ischemia, and 10 min of reperfusion (RP). Glucose was the sole metabolic substrate (Control) or was supplemented with PYR (5 mM) during (a) EQ only (PYREQ group), (b) RP only (PYRRP group), or (c) EQ and RP (PYREQ-RP group). Left ventricular developed pressure (DP) and +/- dP/dt were recorded throughout the experiment. ATP concentrations and intracellular pH were determined by 31P NMR spectroscopy. Myocardial creatinine kinase (CK) activity was assayed at end EQ and end RP. In vitro, purified CK was assayed and, after exposure to H2O2 (200 microM) and increasing concentrations of PYR (0-6 mM) for 10 min, reassayed to determine the antioxidant effect of PYR. In all cases PYR improved recovery of mechanical function at end RP (DP: Control, 11 +/- 1%; PRYRP, 23 +/- 6%; PYREQ, 34 +/- 8%; PRYEQ&RP, 53 +/- 7%; P < 0.05 between all groups and Control). Ischemic contracture was delayed in hearts that received PYR during EQ (PYREQ and PYREQ&RP: 17.8 +/- 0.2 vs 12.5 +/- 0.3 min, P < 0.001). PYR during EQ (PYREQ and PYREQ&RP) led to higher end ischemic ATP levels (32 +/- 4% vs 14 +/- 3%, P < 0.001) and a more acidic end ischemic pH (5.92 +/- 0.02 vs 5.98 +/- 0.03 in Control and PYRRP, P < 0.05). PYREQ&RP showed the highest end reperfusion ATP levels (55 +/- 7% vs 38 +/- 4%, P < 0.05 vs other groups).(ABSTRACT TRUNCATED AT 250 WORDS)

The phosphocreatine overshoot occurs independent of myocardial work

Although the exact mechanism(s) responsible for the phosphocreatine/ATP overshoot have not been completely elucidated, our data demonstrate that the overshoot does not stem from reduced myocardial work, and consequently, reduced utilization of phosphocreatine (PCr). Additionally, we highlight a basic difference in the physiologic responses of skeletal and cardial muscle to work demands. By understanding the bioenergetic derangements which accompany reperfusion injury, one may hope to better salvage post-ischemic myocardium.

Superior vena cava syndrome caused by aneurysm of the innominate artery

Isolated aneurysms or ruptures of the innominate artery are rare causes of the superior vena cava syndrome. We report on a patient who suffered an isolated acute expansion and rupture of an innominate artery aneurysm that precipitated a dramatic superior vena cava syndrome. Immediate repair using modern surgical techniques, cardiopulmonary bypass, profound hypothermia, circulatory arrest, and a Dacron graft rapidly cured the patient of this deadly syndrome.

Detection of pooled secretions above endotracheal-tube cuffs: value of plain radiographs in sheep cadavers and patients

OBJECTIVE

Mechanical ventilation is thought to increase the risk of nosocomial pneumonia by permitting leakage of bacteria-laden gastro-oropharyngeal secretions into the upper airways. The goal of this study was (a) to validate radiographic signs of pooled secretions above endotracheal-tube cuffs (supracuff liquid) in an animal model and (b) to determine whether suctionable pooled supracuff liquid can be identified on bedside radiographs of intubated patients.

MATERIALS AND METHODS

Diagnostic criteria for supracuff liquid were initially validated by three radiologists interpreting 162 randomized radiographs made in an intubated sheep cadaver. The primary criteria included (a) replacement of the normal supracuff lucency with liquid opacity and (b) the formation of a sharp interface between the lucency of the upper edge of the cuff below and the liquid above. Graded infusions of 0, 3, 8, 13, and 23 ml of saline were made in triplicate into the space above the cuff, and radiographs were evaluated for the presence or absence of saline. The validated diagnostic criteria were used by two radiologists to estimate the frequency with which pooled liquid was seen on portable chest radiographs of 47 patients undergoing elective short-term postanesthetic mechanical ventilation.

RESULTS

In the sheep-cadaver model, the diagnostic criteria for supracuff liquid allowed successful differentiation between no liquid, a small amount of liquid (3-8 ml), and a large amount of liquid (13-23 ml; c2, p < .0001). In a clinical study, radiographic signs of supracuff liquid were identified in 57% of 47 patients. In a small subset of patients (n = 18), the estimated liquid volume (mean +/- SEM) was calculated to be 7.8 +/- 1.1 ml (range = 2.1-18.4 ml).

CONCLUSIONS

Radiography is a sensitive means of identifying small volumes of supracuff liquid above the inflated cuffs of endotracheal tubes. Potentially contaminating liquid pooled above the cuff of an endotracheal tube can be identified in about half of patients undergoing short-term mechanical ventilation. Our results suggest the suction of the supracuff space may be a reasonable prophylactic maneuver against nosocomial pneumonia. A much larger study is suggested to investigate the actual relation between pooled supracuff liquid and the development of nosocomial pneumonia.

Protection of the patent internal mammary artery by-pass graft from subsequent sternotomy

OBJECTIVE

We describe a technique to protect the patent internal mammary artery graft from injury by repeat sternotomy.

INTERVENTIONS

The internal mammary artery is dissected as far proximally as possible. The left pleural space is opened widely thus allowing the left lung to protrude through the pleural defect once mechanical ventilation is resumed. The left lung is then interposed between the internal mammary graft and the sternum. The internal mammary artery is thereby protected from adherence to the sternum and injury upon resternotomy.

RESULTS

In two patients in whom this technique was employed repeat sternotomy was easily performed without injury to the internal mammary artery.

CONCLUSIONS

This simple technique effectively protects the patent internal mammary artery bypass graft from injury at subsequent sternotomy.

Ischemic preconditioning preserves end-ischemic ATP, enhancing functional recovery and coronary flow during reperfusion

The mechanisms by which ischemic preconditioning (IPC) protects against reperfusion (RP) injury are unknown. The purpose of this study was to relate IPC to postischemic mechanical function, vascular reactivity, and bioenergetics. Isolated perfused rat hearts were randomized to two groups. Control (CTRL) hearts underwent 25 min of global, 37 degrees C ischemia and 40 min RP. IPC hearts underwent 2.5 min ischemia and 10 min RP followed by 25 min ischemia and 40 min RP (RP40). Left ventricular developed pressure (DP) and coronary flow were continuously measured. 31P NMR spectra determined phosphocreatine and ATP concentrations in parallel hearts every 5 min. Results are means +/- SEM; n = 6/group. Significance was assumed for P < 0.05 by paired (within groups) and unpaired (between groups) t test. CTRL heart DP recovered to 35 +/- 4% of preischemic (PI) DP by RP40 (P < 0.001), while IPC heart DP reached 99 +/- 4% (P = NS vs PI; P < 0.001 vs CTRL). CTRL coronary flow recovered to only 75 +/- 3% of PI (P < 0.001) by RP40. IPC coronary flow exceeded baseline during RP (RP40 = 118 +/- 3%, P < 0.001 vs CTRL; P < 0.05 vs PI). After 25 min ischemia, CTRL heart ATP fell to 40 +/- 4% of PI (P < 0.001) while the IPC group fell to only 60 +/- 4% (P < 0.05 IPC vs CTRL; P < 0.001 vs PI). IPC preserves more end-ischemic ATP compared to CTRL hearts with a resultant improvement in mechanical function during reperfusion. Only preconditioned hearts preserve the adaptive mechanism(s) responsible for postischemic vasodilatation.(ABSTRACT TRUNCATED AT 250 WORDS)

A simple device to assist in needle positioning procedures

At breast biopsy, use of a simple disk that fits into the hub of the needle can facilitate accurate placement of the needle with conventional lesion localization techniques. This disk forms a surface onto which the shadows of the localization crosshairs project so that the operator can advance the needle and maintain its alignment in the direction of the mammography beam by using the field light. The insert has been used successfully in more than 100 procedures.