David Alyono

Alterations of myocardial blood flow associated with experimental canine left ventricular hypertrophy secondary to valvular aortic stenosis.

Experimental renovascular hypertension or supravalvular aortic constriction results in left ventricular hypertrophy and impaired minimum coronary vascular resistance. However, these experimental models expose the coronary arteries to increased intra-arterial pressure, so that hypertensive vascular changes might be responsible for the impaired minimum coronary resistance. This study was performed to test the hypothesis that left ventricular hypertrophy in the absence of increased coronary pressure results in abnormalities of myocardial perfusion. Aortic valve stenosis was produced by plication of the noncoronary aortic cusp of 11 dogs at 6–8 weeks of age. Studies were carried out when the animals reached adulthood; mean left ventricular:body weight ratio was 7.1 ± 0.4 as compared to 4.4 ± 0.3 g/kg in 11 normal dogs (P < 0.01). Under quiet resting conditions, myocardial blood flow measured with microspheres was significantly greater than normal in dogs with aortic stenosis. However, during maximum coronary vasodilation with adenosine, mean left ventricular blood flow in dogs with hypertrophy (3.29 ± 0.39) was substantially less than in normal dogs (6.19 ± 0.54 ml/min per g; P < 0.01), whereas minimum coronary resistance was increased from 14.1 ± 1.7 in normal dogs to 23.7 ± 5.4 mmHg ± min±g/ml (P < 0.01). To examine the response of myocardial perfusion to cardiac stress, blood flow was measured during pacing at 200 and 250 beats/min. Compared with normal dogs, animals with hypertrophy had a subnormal increase in myocardial blood flow during tachycardia; this perfusion deficit was most marked in the subendocardium. These data demonstrate that left ventricular hypertrophy alone, without increased coronary artery pressure, is associated with impaired minimum coronary vascular resistance and with abnormalities of myocardial blood flow during pacing stress.

Value of quantitative cell count and amylase activity of peritoneal lavage fluid.

From January 1974 through July 1979, 1,588 patients underwent diagnostic peritoneal lavage. The test had an accuracy of 98.6%, sensitivity of 94.3%, and specificity of 99.8%. It was true positive in 21.9%, false positive in 0.1%, false negative in 1.3%, and true negative in 76.6%. Fifty-nine patients from the true-positive group had grossly equivocal tests, but had positive lavage results based on quantitative cell count. Thus without cell count the test would have a sensitivity of 78.3%, accuracy of 94.8%, and specificity of 99.8. Eight patients had positive lavage based on WBC count but negative RBC count; all of these patients had bowel injuries. Measurement of lavage fluid amylase resulted in minimal or no improvement in the accuracy (0.06%), sensitivity (0.3%), or specificity (0.0%). Five of six patients with positive amylase levels but grossly negative tests had concomitant positive WBC count. The added cost of the amylase measurement is estimated to be

Saphenous vein graft reconstruction of an unclippable giant basilar artery aneurysm performed with the patient under deep hypothermic circulatory arrest: technical case report.

154,472. Peritoneal lavage has high accuracy, sensitivity, and specificity. Cell counts significantly improve sensitivity. Patients with a grossly equivocal test but with a positive cell count should undergo laparotomy. The lavage-fluid amylase measurement is costly and is of insignificantly yield.

Myocardial blood flow during exercise in dogs with left ventricular hypertrophy produced by aortic banding and perinephritic hypertension.

OBJECTIVE AND IMPORTANCE Effective treatment for unclippable giant vertebrobasilar aneurysms remains unclear. We present the first reported case of a giant vertebrobasilar aneurysm being successfully treated with trapping of the aneurysm and internal carotid artery to basilar artery bypass with a saphenous vein graft that was performed with the patient under hypothermic circulatory arrest. CLINICAL PRESENTATION A 15-year-old female patient with a history of probable subarachnoid hemorrhage and chronic headaches presented with a relatively acute exacerbation of her headache, nausea, vomiting, and weakness. Imaging studies revealed a 4 x 4 x 3-cm vertebrobasilar aneurysm, supplied by an angiographically dominant right vertebral artery and causing significant brain stem compression. INTERVENTION Initially, a petrosal approach with a hearing-preserving partial labyrinthectomy was used to perform a right external carotid artery to posterior cerebral artery bypass with saphenous vein. Delayed occlusion of the right vertebral artery with an intraluminal balloon was planned; however, intraoperative angiography revealed poor graft flow, presumably because of the small size of the posterior cerebral artery. Postoperative graft occlusion was anticipated. During this same time interval, the patient deteriorated neurologically. Brain imaging failed to reveal evidence of cerebral infarction. The patient underwent subsequent surgery. After a total petrosectomy, the aneurysm was trapped, an aneurysmectomy was performed, and, with the patient under deep hypothermic circulatory arrest, a new interposition saphenous vein graft was inserted between the internal carotid and basilar arteries. Excellent flow was observed angiographically. At her 4-month follow-up examination, the patient had improved to near baseline. CONCLUSION We present a technically challenging but safe and definitive treatment option for an unclippable giant vertebrobasilar aneurysm. Using cranial base approaches and hypothermic circulatory arrest techniques, aneurysmal trapping and successful bypass grafting directly into the basilar artery was performed.

Magnesium deficiency prolongs myocardial stunning in an open-chest swine model

This study tested the hypothesis that for similar degrees of left ventricular hypertrophy, subendocardial blood flow would be facilitated by the increased diastolic coronary perfusion pressure associated with arterial hypertension, as compared with hypertrophy produced by banding the ascending aorta. Left ventricular hypertrophy was produced with perinephritic hypertension in seven adult dogs and by banding the ascending aorta in nine adult dogs. Left ventricular/body weight ratios were 6.15 +/- 0.59 g/kg in the hypertensive animals and 6.87 +/- 0.47 g/kg in dogs with aortic banding, as compared with 4.23 +/- 0.23 g/kg in seven normal dogs (p less than .01). Studies were performed at rest and during two stages of treadmill exercise to achieve heart rates of 195 and 260 beats/min. Diastolic aortic pressure was increased in animals with hypertension but not in dogs with aortic banding. Systolic ejection period was prolonged in dogs with aortic banding but not in hypertensive dogs. Mean blood flow per gram of myocardium measured with microspheres was similar at rest and during light exercise in all three groups of animals, whereas during heavy exercise blood flow was significantly greater than normal in both groups with hypertrophy. In normal dogs subendocardial/subepicardial (endo/epi) flow ratios did not change significantly during exercise. In both groups with hypertrophy, endo/epi ratios were normal at rest but decreased significantly during exercise. During heavy exercise the endo/epi ratio decreased to 0.73 +/- 0.08 in dogs with aortic banding as compared with 1.07 +/- 0.12 in hypertensive dogs (p less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Management of AIDS-Related Pneumothorax

The effect of magnesium deficiency on postischemic myocardial dysfunction (myocardial stunning) in an open-chest swine model was studied. Twelve swine were assigned either to low magnesium diet or control diet. Myocardial stunning was assessed by measuring regional wall thickening by epicardial Doppler before and after brief occlusion (8 min) of the left anterior descending coronary artery. Serum magnesium levels decreased significantly in the experimental group only. Glutathione levels were 42.6% lower in the magnesium deficient swine than in controls. Stunning time was significantly prolonged from 32.8 +/- 3.1 min in the control group to 43.8 +/- 4.6 min in the hypomagnesemic swine. In conclusion, magnesium deficiency is associated with prolonged recovery from myocardial stunning.

Defining end systole for end-systolic pressure-volume ratio.

BACKGROUND Pneumothorax (PTX) occurs in 5% of patients with acquired immunodeficiency syndrome (AIDS) infected with Pneumocystis carinii pneumonia, and up to 50% of those will die during hospitalization. The treatment strategies for managing AIDS-related PTXs are often complex and ineffective at treating the PTX, and they can prolong hospitalization. METHODS We reviewed our experience with 36 male patients with AIDS treated for 44 PTXs over a 2.5-year period to determine if a particular therapeutic approach could allow for an earlier recovery and effective treatment of the PTX. All patients had current or prior history of Pneumocystis carinii pneumonia infection, and the CD4+ T-lymphocyte counts were less than 100/microL in 100%. RESULTS Twenty-seven patients with 31 PTXs were discharged from the hospital. Of these 31 PTXs, 21 had resolved at the time of the patients discharge from the hospital, and the other 10 PTXs were converted from Pleurevac (Deknatel, Inc, Fall River, MA) drainage to a Heimlich valve for persistent bronchopleural fistula after more than 15 days of conventional treatment. The PTXs were effectively managed by tube thoracostomy alone in 18/44 PTXs (41%), tube thoracostomy plus sclerosing therapy in 2/8 PTXs (25%), and thoracotomy with blebectomy and pleurodesis in 1/3 PTXs (33%). Nine of 11 of the procedure-related PTXs responded to tube thoracostomy alone; the other 2 PTXs were converted from Pleurevac drainage to a Heimlich valve and allowed for patient discharge from the hospital in less than 10 days. Nine patients with 13 PTXs died during hospitalization. Four of these 9 patients (44%) had bilateral PTXs, and 8/9 (89%) were being treated by tube thoracostomy with Pleurevac suction for persistent bronchopleural fistula in the intensive care unit at the time of death. The 8 patients treated for 10 PTXs with a Heimlich valve had effective management of the PTX, had no morbidity associated with the Heimlich valve and no in-hospital mortality, and were discharged from the hospital to home or a hospice setting. CONCLUSIONS The management of AIDS-related PTXs is complex and often associated with a destructive pulmonary process and other systemic disease conditions related to AIDS that result in ineffective resolution of the PTX, a prolonged hospitalization, and a high mortality. In our experience, there is a lesser role for managing the PTXs with sclerosing therapy or thoracotomy. Patients with advanced AIDS complicated by PTXs with bronchopleural fistula can be converted from a Pleurevac drainage system to a Heimlich valve with no apparent morbidity or mortality, and managed as an outpatient, thereby potentially shortening hospitalization and facilitating an earlier discharge from an acute care setting.

Long Term Model for Evaluation of Myocardial Metabolic Recovery following Global Ischemia

The end-systolic pressure-volume (ESPV) ratio (Emax) has recently been accepted as a valid cardiac contractility index. However, in vivo, it is difficult to define end systole (ES) precisely. This study was designed to analyze the effects of eight different ES definitions on Emax. Nine chronically instrumented dogs were studied prior to and during the sequential infusions of phenylephrine (0.2 mg/min), epinephrine (2.0 micrograms/min), and dobutamine (10 micrograms/kg/min). Left ventricular (LV) dimensions and pressure were measured with sonomicrometers and micromanometer. ES was defined at peak LV pressure (PLVP), end-ejection, dp/dt min, 10, 20, 30 msec before dp/dt min, minimum volume before dp/dt min, and left-upper-corner of pressure volume loop (LUC). Although ESPV relationship from each definition was linear (mean r 0.89 +/- 0.3, range 0.76 to 0.99) and sensitive to inotropic changes, the Emaxs were not all the same. The r was highest with LUC (mean 0.94 +/- .02, range 0.90 to 0.99) and lowest with PLVP (mean 0.85 +/- 0.03, range 0.76 to 0.92). Emax from PLVP was least sensitive to epinephrine and dobutamine infusions. Thus, in order to compare different values of Emax, the definition of ES must be precise and consistent. Although all the above eight definitions of ES appeared to produce reasonable ESPV relationship, PLVP appeared to be the worst while LUC appeared to be the best ES definition for determining Emax.

Platelet membrane glycoproteins and microvesicles in blood from postoperative salvage: a study in cardiac bypass patients

Myocardial ATP levels remain depressed following significant periods of ischemia (Isc) despite reperfusion (Rpf). Neither the rate of in vivo ATP return following global Isc nor the factors which influence recovery have been defined. In order to determine the time course to complete the return of ATP levels and evaluate methods of enhancing recovery of ATP levels, we have devised a chronic canine model of global Isc. In this model serial ventricular biopsies can be taken in the awake animal over several days without reoperation which allows an investigation of the recovery of the myocardium following a uniform global insult to be performed. Recovery of ATP levels has been shown to depend, at least in part, on the availability of precursors and the activity of the ATP regenerating enzymes. Because complete recovery of ATP levels takes days, short term (hours) models have limitations. Previous attempts at enhancing ATP recovery following Isc have been only partially successful because either the degree of depression was not great or the period of observation was short, resulting in incomplete return. To identify the best precursor choice, we previously measured the activity of the AMP regenerating enzymes, adenosine kinase (AdK) (adenosine----AMP) and adenine phosphoribosyl transferase (APRT) (adenine----AMP). Because APRT activity was 20 fold higher than AdK with similar Km values for substrates, it appeared that adenine (A) is preferred to adenosine for AMP regeneration in the dogs myocardium. The formation of 5-phosphoribosyl 1-pyrophosphate (PRPP) may also be rate limiting and, therefore, the effect of ribose (R) on ATP recovery was also evaluated. Recovery of ATP levels was assessed in three groups: (1) normal saline (NS), (2) A (20 mM) in normal saline (A/NS) or (3) A with R (80 mM) in normal saline (A/R) were infused (1.0 ml/min) into the right atrium of dogs for 48 hours following Isc. In all groups, ATP levels fell to between 46-60% of pre-Isc levels during Isc. In the NS dogs, ATP levels continued to fall slightly to 46% pre-Isc levels during the first four hours of Rpf after Isc. By 24 hours no appreciable recovery had occurred and the measured ATP was only 51% of the pre-Isc value. Even by seven days, ATP had not returned fully, and by extrapolation, complete recovery required 9.9 +/- 1.4 days. Treated dogs showed, however, that ATP recovery could be significantly enhanced.(ABSTRACT TRUNCATED AT 400 WORDS)

Global left ventricular contractility in three models of hypertrophy evaluated with Emax

BACKGROUND: Transfusion of blood collected by intraoperative and postoperative salvage systems has been linked to the development of thrombocytopenia and disseminated intravascular coagulation. Although functional defects have been reported in platelets from unwashed salvaged blood, platelet membrane glycoprotein (GP) composition, a potentially important determinant of function and survival, has not been studied.