Effect of inosine in the normal and reperfused rat heart

Inosine is a positive inotropic agent and dilates coronary blood vessels. During ischemia, inosine infusion increases blood flow, resulting in decreased myocardial damage. We wished (a) to determine inosine's effect in isolated rat hearts and (b) to determine if inosine attenuates myocardial dysfunction after transient global ischemia. Developed left ventricular pressure (LVP), LV dP/dt, and coronary perfusion pressure were monitored in hearts receiving Krebs-Henseleit buffer (KHB) (n = 10) or KHB + 2 mM inosine (n = 4). KHB + 2 mM inosine significantly reduced coronary perfusion pressure by 21% but had no effect on developed LVP or LV dP/dt. Hearts receiving KHB (n = 6) or KHB + 2 mM inosine (n = 5) were subjected to 15-min global ischemia followed by 30-min reperfusion with KHB. Recovery of LVP, LV dP/dt, the incidence of arrhythmias, and the time to peak recovery of developed LVP was not different between groups. In two additional hearts, KHB + 2 mM inosine administered during reperfusion had no effect on developed LVP, LV dP/dt, or coronary perfusion pressure. Thus, unlike other preparations, inosine pretreatment did not significantly affect the time course of postischemic functional recovery of rat myocardium.

Signal-averaged electrocardiography. Promising tool for predicting sudden cardiac death

Signal-averaged electrocardiography has shown great promise as an adjunct in identifying patients at risk for sudden cardiac death. Clearly, much research remains to be done. Methods and criteria must be standardized so studies can be compared and the most effective ways in which to use this technology can be determined.

The value to the anesthesia-surgical care team of the preoperative cardiac consultation

A retrospective analysis of 202 consultations for preoperative cardiology evaluation was conducted. The most common problems generating the consultation were: (1) abnormal electrocardiogram, 45 patients; (2) chest pain, 36 patients; (3) history of myocardial infarction, 27 patients; (4) dysrhythmia, 25 patients; and (5) hypertension, 23 patients. The most common diagnoses by the consultants were: (1) arteriosclerotic heart disease, 46 patients; (2) angina, 20 patients; and (3) hypertension, 40 patients. Mitral valve prolapse was the most common valvular disease (18 patients). Of the consultation requests, 108 asked for an evaluation; 79 asked for a "clearance"; 9 did not specifically ask for anything; and 6 asked a highly specific question. Most consultations provided a diagnosis (96%), addressed the problem (80%), and provided logical recommendations (96%). A minority of the consultations "cleared" a patient (28%), provided for follow-up care (41%), or suggested intraoperative monitoring techniques (41%). Out of the 189 patients who eventually had surgery, 137 patients had no change in their preoperative therapy, while 52 patients had a change in preoperative therapy. There was no difference in the incidence of complications between these two groups. An important finding was that 15% of the study group (31 patients) had disease processes (hypertension and angina) that were newly diagnosed by the consultant or felt to be not adequately treated before the consultation. It is concluded that few requesting anesthesiologists and surgeons ask for clarification of a specific problem, while most responses from the cardiology consultants provided necessary information. In addition, the preoperative cardiac consultation was found to identify medical conditions requiring long-term care and follow-up.

Errors in the determination of left ventricular functional parameters

Gated blood-pool scans of the left ventricle are routinely employed for determination of the left ventricular ejection fraction. Recently, attempts have been made to evaluate other left ventricular functional parameters. These values include peak emptying rate (PER), time to peak emptying rate (TPER), peak filling rate (PFR), and time to peak filling rate (TPFR). In studying these parameters clinically, we identified many software errors and assumptions that impact on these values. These errors may also affect the determination of left ventricular ejection fraction (EF). We conclude that before any serious investigation of left ventricular functional parameters is undertaken, a detailed evaluation and standardization of the acquisition and edge detection algorithms must be performed.

Reversal of recalcitrant cardiac allograft rejection with methotrexate

Refractory cardiac transplant rejection is a major therapeutic dilemma. The effectiveness of methotrexate (MTX) in autoimmune diseases prompted us to explore its efficacy in 10 cardiac transplant recipients, aged 20-53 years (39 +/- 13 years; mean +/- SD), with biopsy evidence of drug-refractory cardiac allograft rejection. Nine cardiac transplant recipients were maintained on triple antirejection therapy (cyclosporine, azathioprine, and prednisone), and the remaining recipient was maintained on cyclosporine and prednisone. Rejection episodes treated with MTX occurred 20-422 days (165 +/- 137 days) after transplantation and were the sixth episode of rejection for one recipient, the third for four recipients, the second for four recipients, and the first for one recipient. Before MTX administration, cardiac allograft rejection persisted despite intensified immunosuppression including OKT3 antibody. MTX, given intravenously, orally, or by both routes at a dose of 10-175 mg (85 +/- 62 mg), reversed rejection in nine of 10 recipients (90%) within 7-63 days (26 +/- 18 days). Elevated pulmonary artery wedge pressures were reduced to normal levels after MTX therapy (15.2 +/- 3.5 before vs. 10.6 +/- 3.0 mm Hg after; p less than 0.05). Leukopenia occurred in five cardiac transplant recipients after treatment with MTX. Adverse reactions to MTX resolved after MTX therapy was discontinued in all but one recipient. This recipient received one of the larger MTX doses (150 mg) and developed fatal Pseudomonas pneumonia. Twelve moderate rejection episodes recurred in nine recipients, seven episodes of which were successfully re-treated with MTX. Two of these seven recipients have now been rejection-free for 15 months. Of five recurrent episodes of cardiac transplant rejection not treated with MTX, two could not be reversed and were fatal. MTX may be a valuable drug for reversing refractory cardiac allograft rejection. Before MTX therapy gains wider use, however, a clearer understanding of its enhanced ability to suppress the bone marrow is needed.

Effects of the free radical scavenger DMTU and mannitol on the oxygen paradox in perfused rat hearts

The oxygen paradox refers to the abrupt release of cytoplasmic enzymes and severe cellular disruption that occurs following reoxygenation of anoxic perfused hearts. In this study, the ability of a series of oxygen-derived free radical inhibitors and scavenging agents to protect isolated perfused rat hearts from the oxygen-induced enzyme release following 30 or 60 mins of anoxic perfusion (oxygen paradox) and cumene hydroperoxide-induced injury was evaluated. Malondialdehyde (MDA) release, an indicator of lipid peroxidation, and creatine kinase (CK) release, an indicator of cellular injury, were monitored. We evaluated five agents previously reported to scavenge or inhibit the formation of oxygen free radicals. The putative hydroxyl radical scavengers dimethylthiourea (DMTU) and mannitol; catalase, an agent protective against peroxide injury; allopurinol, an inhibitor of xanthine oxidase; and albumin, a non-specific protein control, were evaluated. Coronary flow rates and myocardial temperature were continuously monitored to ensure uniform perfusion conditions. The MDA assay was carefully monitored by constructing standard curves on each experimental day. Addition of 20 microM cumene hydroperoxide to oxygenated perfused hearts caused peroxidative cell injury as evidenced by significant MDA and CK release in the coronary effluent. DMTU and catalase provided near complete protection from cumene hydroperoxide-induced cell injury but did not reduce CK release from hearts subjected to either the mild (30-min) or the severe (60-min) oxygen paradox (reoxygenation-induced injury). Allopurinol caused a significant reduction in MDA release but not CK release from oxygen paradox-injured hearts. Allopurinol and albumin had no significant effect on MDA release from cumene-hydroperoxide-injured hearts. Catalase (300 U/ml) caused a mild but not statistically significant reduction in MDA release from cumene hydroperoxide injury but did not provide protection from the oxygen paradox at either injury level. Mannitol (120 mM), in contrast to DMTU, was ineffective in reducing cumene-induced injury but showed a significant protective effect against oxygen paradox-induced damage. It is concluded that the ability of mannitol to reduce reoxygenation-induced CK release in the oxygen paradox may be due to its osmotic activity and consequent ability to prevent cellular swelling rather than its activity as an oxygen-free radical scavenger.

Decreased alpha 2-adrenergic receptors on platelet membranes from diabetic patients with autonomic neuropathy and orthostatic hypotension

Platelet adrenergic receptors were studied in normal subjects and diabetic patients with autonomic neuropathy to determine the relationship between adrenoreceptor status and orthostatic hypotension. The binding of [3H]clonidine and [3H]yohimbine to platelet membranes was measured in diabetic patients with autonomic neuropathy and orthostatic hypotension (n = 12) and without orthostatic hypotension (n = 11), diabetic patients without autonomic neuropathy (n = 12), and normal subjects (n = 9). Mean basal and standing plasma norepinephrine levels were not different in the four groups, and there was no relationship between orthostasis and norepinephrine responses. The diabetic patients with orthostatic hypotension had a significantly greater fall in mean blood pressure [31 +/- 2.8 (+/- SE) mm Hg] than any of the other three groups. Diabetic patients with diabetic autonomic neuropathy and orthostatic hypotension had a 30-40% decrease in number of platelet alpha 2-adrenergic receptors, as demonstrated by [3H]clonidine and [3H]yohimbine binding. The maximum number of binding sites for clonidine was 34 +/- 2.8 (+/- SE) fmol/mg protein in normal subjects, 27.4 +/- 3.4 in diabetic patients with neuropathy, 26 +/- 2.5 in diabetic patients with autonomic neuropathy without orthostatic hypotension, and 20.4 +/- 3.8 fmol/mg protein in diabetic patients with autonomic neuropathy with orthostatic hypotension (P less than 0.001). The maximum number of binding sites for yohimbine was 112 +/- 12.6 in normal subjects, 127 +/- 10 in diabetic patients without orthostatic hypotension, and 87 +/- 12.4 fmol/mg protein in patients with diabetic autonomic neuropathy with orthostatic hypotension (P less than 0.001). Reduced platelet alpha 2-receptors are associated with postural hypotension in diabetic autonomic neuropathy. If applicable to the postjunctional alpha 2-adrenergic receptor on sympathetic neurons, reduced vascular responses to changes in posture would be expected despite normal or enhanced norepinephrine secretion.

Impaired hypoxic ventilatory drive in diabetic patients with autonomic neuropathy

The mortality of diabetic patients with autonomic neuropathy (DAN) is higher than that in those without autonomic neuropathy (DM). To test the hypothesis that this may be due to respiratory rather than cardiac dysfunction, we evaluated ventilatory responses to isocapnic-hypoxic and hyperoxic-hypercapnic conditions in 14 diabetic patients (8 DAN and 6 DM) and compared the results with those in 8 normal subjects. In all groups tested there was a significant linear correlation between end-tidal CO2 and minute ventilation and between end-tidal CO2 and mouth occlusion pressure (p100), as an index of the drive to breathe. There were no significant differences between the slopes and intercepts in the groups tested. A significant linear correlation was found between the O2 saturation and both minute ventilation and p100. There were no significant differences in the relationship between minute ventilation and O2 saturation, but the slopes and the intercepts of the regression lines of p100 vs. O2 saturation were significantly different in the DAN compared with those in normal subjects and DM. Additionally, five of eight patients with DAN lost their ventilatory drive and ventilatory responses to hypoxemia compared with only one of six DM. These findings suggest that a disorder in the ventilatory response to hypoxemia exists in some DAN.

Arrhythmias documented by 24-hour continuous ambulatory electrocardiographic monitoring in young women without apparent heart disease

Results are reported of 24-hour ambulatory ECG recordings in 50 young women without apparent heart disease. During waking periods, maximum (sinus) rates ranged from 122 to 189 beats/min (bpm) (153 +/- 14 mean +/- SD) and minimum rates from 40 to 73 bpm (56 +/- 7). During sleeping periods, maximum and minimum rates ranged from 71 to 128 bpm (105 +/- 13) and from 37 to 59 bpm (48 +/- 6), respectively. Thirty-two subjects (64%) had atrial premature beats, with only one subject (2%) having greater than 100 beats/24 hrs. Twenty-seven subjects (54%) had ventricular premature beats, with only three subjects (6%) having greater than 50 beats/24 hrs. One subject (2%) had one three-beat episode of ventricular tachycardia. Two subjects (4%) had transient type I second-degree atrioventricular block.