Whole blood platelet aggregation is not affected by cigarette smoking but is sex-related

1. In normal subjects, 18-49 years old, the effects of the smoking habit (greater than 10 cigarettes/day) and the act of smoking two cigarettes over 10 min were studied on whole blood platelet aggregation (in vitro impedance method). 2. Acute smoking (n = 10) did not affect platelet aggregation to ADP, collagen or to platelet activating factor (PAF) nor thromboxane B2 production during aggregation. There was no difference between smokers (n = 13) and non-smokers (n = 10). However, aggregation to all aggregants was greater in females (n = 11) than males (n = 12) (ADP and collagen, P less than 0.001; PAF, P less than 0.01; ANOVA). 3. Although others have obtained diverse results studying platelet-rich plasma, the absence of an effect of cigarette smoking on whole blood platelet aggregation is consistent with many of those observations. Greater in vitro aggregability in females than males is consistent with the few studies of platelet-rich plasma. It seems unlikely that the role of cigarette smoking as a risk factor for ischaemic heart disease is related to a direct effect on platelet aggregability.

Hypoxemia after gastric bypass surgery for morbid obesity

Fifty-six patients who underwent Roux-en-Y gastrojejunostomy for morbid obesity had arterial blood gas analysis before surgery and during the first five postoperative days. Preoperatively, seven subjects were hypoxemic and three were hypercapneic. Twenty-four hours after gastric bypass, 75% of the patients had an arterial oxygen pressure (Pao2) less than 60 mm Hg. Compared with preoperative measurements, blood gas values on the first postoperative day showed a 13.7-mm Hg decrease in the mean arterial Pao2 and a 5.0-mm Hg increase in the mean arterial carbon dioxide pressure. Arterial Pao2 determinations on the third, fourth, and fifth postoperative days returned toward, but remained significantly less than, paired values obtained before surgery. Patients with hypoxemia after gastrojejunostomy were significantly older and had significantly lower preoperative arterial Pao2 measurements than patients who were not hypoxemic after surgery. Weight, body mass index, and preoperative spirometric measurements did not distinguish between those patients who did and did not become hypoxemic postoperatively. We conclude that hypoxemia commonly follows gastric bypass for morbid obesity, and thus we recommend that all patients undergoing this procedure be treated with supplemental oxygen for at least the first three postoperative days.

Effect of beta-adrenergic blockade on the results of exercise testing related to the extent of coronary artery disease

Maximal treadmill testing was carried out in 50 patients with angiographically documented coronary artery disease (CAD) in the presence and absence of beta-adrenoceptor blockade. The results were related to the extent of CAD and interpreted relative to the clinical value of exercise testing. Maximal heart rate and systolic blood pressure were significantly lower during treatment with beta-blocking drugs. The average exercise duration was 1.3 +/- 1.9 minutes greater (+/- standard deviation), regardless of coronary anatomy. Of the 20 subjects with 3-vessel or left main CAD (severe CAD), 8 patients completed 3 stages (9 minutes) of exercise during treatment; only 4 did so without treatment. Angina was significantly more often the limiting symptom with severe CAD, and this association was abolished by beta blockade; 1 of 20 with severe CAD completed 3 stages of exercise and was not limited by angina without beta-blocking treatment, whereas 7 had these features during beta-blockade therapy. Maximal ST-segment depression was not related to the extent of CAD with or without therapy. Beta blockade suppressed the occurrence of ST depression, or delayed its appearance by an average of 2.0 +/- 2.3 minutes and reduced its severity by 0.5 +/- 0.9 mm. All tests in which ST depression was completely suppressed were associated with inadequate heart rate response, regarded as diagnostically inconclusive rather than negative. However, during beta-blocking treatment, 14 tests (28%) were inconclusive, which, in routine practice, would have necessitated repeat testing.(ABSTRACT TRUNCATED AT 250 WORDS)

The measurement of plasma thromboxane B2 and the effect of smoking

Plasma thromboxane B2 (TxB2) was measured by radioimmunoassay using an iodinated ligand following extraction and further purification by thin layer chromatography. Venous blood was sampled into a syringe containing the cyclooxygenase inhibitor meclofenamate. Normal levels, 15 pg/ml (s.d. = 8, n = 21), were lower than usually reported and measured values increased several fold over 20 min sampling from an indwelling needle. With appropriate sampling there was a statistically insignificant increase in plasma TxB2 after subjects smoked two cigarettes (n = 11). An average decrease occurred in a control group (n = 10) and the difference between groups was of borderline significance (P less than 0.05). Smoking did not change TxB2 production associated with platelet aggregation induced in vitro by collagen, whereas plasma adrenaline increased significantly. The results emphasize the importance of the technique of sampling and assay in the measurement of plasma TxB2.

A comparison of intravenous and intracoronary streptokinase in acute myocardial infarction

A randomised study of intravenous and intracoronary streptokinase therapy was carried out in 20 subjects with acute myocardial infarction and angiographically confirmed complete obstruction of the associated coronary artery. Two dose levels of therapy were used. Although more recanalisations occurred with intracoronary than intravenous therapy at the low dose levels, overall there was not a significant difference between the two groups; one million IU intravenously over 20 minutes recanalised four of five arteries. While seven of nine recanalisations with intracoronary therapy occurred within an hour, only two of five with intravenous therapy did so. Hence prolonged angiographic observation is necessary to document recanalisation with intravenous therapy adequately. Nevertheless, the time disadvantage of large dose intravenous therapy is not great and it may yet prove as effective as, and more practical than, intracoronary therapy.

Cigarette smoking and ventricular arrhythmia in coronary heart disease

With use of 24-hour ambulatory electrocardiographic monitoring, the effect of 1 hour of cigarette smoking on cardiac rhythm in 73 patients with coronary heart disease was studied. Fifteen subjects had no arrhythmia; 37 subjects had fewer than 2 atrial or ventricular premature complexes (APCs or VPCs)/hour, with APCs possibly related to smoking in 2 and VPCs related to smoking in 1. Nineteen subjects had more than 2 VPCs/hour (range 4 to 368) and had 16 +/- 29 VPCs/hour (+/- standard deviation) less during than before smoking (p less than 0.05), associated with an increase in heart rate of 4.6 +/- 6.8 beats/min (p less than 0.01). In none of the 9 subjects with unifocal VPCs did multiform beats develop during or after smoking, whereas 3 of 10 subjects with multiform VPCs had only unifocal beats during and immediately after smoking. In 1 of these 19 subjects, frequent APCs developed during smoking. One other subject had frequent APCs unaffected by smoking and another had sinoatrial block, which disappeared during smoking on 1 of 3 monitorings. In conclusion, no sustained or high-grade ventricular arrhythmia was provoked by smoking; although APCs may have been related to smoking in a few persons, the frequency and complexity of VPCs tended to be reduced in these subjects with coronary artery disease.

Increased protein synthesis and degradation in the dog heart during thyroxine administration

Mongrel dogs were injected with 1-thyroxine (0.5 mg/kg body weight) for 7 or 14 days and fractional synthesis rates of total, sarcoplasmic and myofibrillar protein were measured in the left ventricle using continuous intravenous infusion of [14C]tyrosine. The synthesis rate of total protein was increased from 7.2% to 9.2% per day and 10.9% per day after 7 and 14 days respectively. The normally lower synthesis rate of myofibrillar protein was stimulated proportionately more than that of sarcoplasmic protein, increasing from 6.0% to 11.7% per day over 14 days, while that of sarcoplasmic protein increased from 10.3% to 13.1% per day. There was a significant increase in left ventricular RNA concentration and decrease in collagen, concentration. Left ventricular weight/body weight was 17% greater than normal after 7 days but the lack of further change in the second week suggests that, after the early development of hypertrophy, protein degradation was also increased, along with the markedly increased synthesis rate.

beta-Adrenoceptors in the hypertrophied right ventricle of the dog with pulmonary stenosis

1. Right ventricular hypertrophy was produced in dogs by banding of the pulmonary artery for 28 days (n = 7) and results were compared with those in sham-operated dogs (n = 5). 2. Myocardial noradrenaline and adrenaline levels were depressed in both the hypertrophied right ventricle and the non-hypertrophied left ventricle and plasma levels were increased compared to the control dogs. 3. Myocardial beta-adrenoceptors were assessed in membrane preparations of both ventricles by 3H-dihydroalprenolol binding. No change in binding site concentration (pmol/mg membrane protein) or in binding affinity was found in either the hypertrophied right ventricle or in the left ventricle. 4. Divergent results of studies on beta-adrenoceptors in ventricular hypertrophy are difficult to reconcile.

Collagen synthesis and content in right ventricular hypertrophy in the dog

The fractional synthesis rate of collagen (the percent of total ventricular collagen synthesized in one day) was measured in the hearts of normal dogs and those with pulmonary artery stenosis using a continuous 6-h intravenous infusion of [14C]proline. The fractional synthesis rate in normal ventricles was slow, 0.56%/day, and it increased eightfold to 4.8%/day in the hypertrophying right ventricle after 5 days. After 12 and 28 days the synthesis rate was still significantly greater than in the control left ventricle, being 2.6 and 1.3%/day, respectively. However, the synthesis rate of noncollagen protein was significantly greater than normal at 5 days only. The collagen content (expressed as a mass fraction) of the right ventricle decreased over the first 12 days of hypertrophy but by 28 days was restored to the normal right ventricular value of 9.6 mg/g wet wt tissue. The total amount of collagen in the hypertrophied ventricle calculated from the synthesis rates was in accord with that measured chemically. In normal dogs the collage content of the right ventricle was greater than that of the left, and the epicardium contributed substantially to the total collagen in the ventricular walls.

Randomized controlled trial of vasodilator therapy after myocardial infarction

Hemodynamic changes and mortality and morbidity were compared in a randomized controlled trial of sodium nitroprusside after acute myocardial infarction. Fifty patients with a mean pulmonary capillary wedge pressure of more than 20 mm Hg within 24 hours of acute infarction were randomly assigned to one of two groups: 25 patients treated with nitroprusside and 25 treated with furosemide. Nitroprusside rapidly produced a sustained decrease in systemic vascular resistance and increase in cardiac index (thermodilution). After 1 hour the cardiac index had increased 16 +/- 3 (mean +/- standard error of the mean) percent (p less than 0.001) compared with a decrease of 7 +/- 3 percent with administration of furosemide (p less than 0.01). Differences in systemic vascular resistance and cardiac index in the two groups persisted throughout the 48 hour treatment period (p less than 0.001). Pulmonary capillary wedge pressure decreased rapidly with nitroprusside and slowly with furosemide so that, although it was significantly lower in the former group overall (p less than 0.001), by 48 hours the values were not different. Although beneficial acute hemodynamic effects of nitroprusside were demonstrated, there was no difference in mortality or in morbidity assessed clinically, by chest X-ray film, echocardiogram or graded treadmill stress testing after 6 months or 1 year.

The influence of heart rate on digoxin-induced inhibition of myocardial Na+-K+-ATPase activity in the dog

1. Groups of sedated dogs were studied at spontaneous heart rates (HR), 55-100/min, or at paced HR 200/min, with or without intravenous digoxin administration. After 60 min, active rubidium uptake (86 Rb+) of ventricular samples was determined in vitro. 2. Untreated fast and slow HR groups had similar uptakes. Following digoxin, 0.08 mg/kg, uptake was less at fast than slow HR (63.8, s.e.m. = 4.5 v. 87.5, s.e.m. = 5.0 pmol/mg LV/15 min, P less than 0.01). After 0.125 mg/kg, values were again lower in the fast HR group in which five of seven developed ventricular tachycardia. 3. Heart rate does not alter in vitro activity of myocardial Na+-K+-ATPase but does influence inhibition of the enzyme resulting from digoxin administration.

Cardiac beta-adrenoreceptors in the thyroxine-treated dog

1. Myocardial beta-adrenoreceptors, assessed in membrane preparations of left ventricle by 3H-dihydroalprenolol binding, were compared in dogs following thyroxine administration (n = 6), aorto-caval fistula (n = 12), and in normal dogs (n = 7). 2. Left ventricular hypertrophy occurred in response to both aorto-caval fistula and thyroxine treatment. Yield of myocardial membrane between the different groups was not significantly different. 3. Binding site concentration (pmol/mg membrane protein) in dogs with aorto-caval fistulae was similar to that in normal dogs and was not significantly influenced by the presence or absence of cardiac failure, degree of hypertrophy or duration of fistula. 4. Thyroxine-treated dogs had an increased concentration of binding sites (c. 1.8-fold) compared with both fistula and normal groups, while binding affinities were similar in all groups. 5. The data suggest that beta-adrenoreceptor concentrations in myocardium increase as a direct result of thyroid hormone action rather than as a result of secondary haemodynamic changes or ventricular hypertrophy.

Age dependence of myocardial Na+-K+-ATPase activity and digitalis intoxication in the dog and guinea pig

Infants and young animals tolerate higher doses of digitalis glycosides, relative to body weight, than adults. One possible explanation for this could be an age-dependent difference in the myocardial digitalis receptor, the Na+-K+-ATPase. Two functions of this enzyme were studied in adult, 1- and 6-week-old dogs and guinea pigs: in vitro myocardial uptake of rubidium (86Rb) and binding of ouabain. In guinea pigs, rubidium uptake (pmol Rb/mg LV per 15 min) was: 1 week old: 100.9 +/- 7.1 (mean +/- SE); 6 week: 79.8 +/- 6.7 adult: 55.2 +/- 7.9; (1 week: 6 week: P less than 0.025; 1 week: adult, P less than 0.001; 6 week: adult, P less than 0.025). Similarly in dogs, rubidium uptake was significantly greater at 1 week than at 6 weeks (208 +/- 13 vs. 144 +/- 9; P less than 0.001) and the latter greater than in adults (111 +/- 4) (P less than 0.005). Other groups of anesthetized adult and 6-week-old dogs were given digoxin, 0.3 mg/kg, iv. The young dogs took significantly longer to become cardiotoxic (17.3 +/- 3.4 min vs. 9.3 +/- 1.4 min; P less than 0.025), while their myocardial digoxin uptake was at least as great. Rubidium uptake showed an average decrease of 56% after digoxin but residual uptakes were not different in the two groups. Data for ouabain binding showed similar differences between the various groups of dogs studied. Increased myocardial Na+-K+-ATPase activity, reflected in greater active cation transport and specific enzyme binding, has been demonstrated in young animals and may be partly responsible for their greater tolerance to digitalis glycosides.

Exercise testing and thallium-201 myocardial imaging in relation to coronary artery disease in patients with severe aortic valve disease

Thirty-three patients with aortic valve disease, fifteen with regurgitation, eleven with stenosis and seven with mixed disease, undergoing assessment for valve replacement which included adequate coronary angiography, were studied. A symptom limited graded treadmill exercise test was undertaken with administration of 40-70 MBq of 201Tl. Myocardial imaging was started within 15 minutes and repeated after four hours using a 37 PM tube Searle gamma camera. Myocardial images were read independently by three observed. Of the 33 sets of images, 21 were -ve, 5 +ve, 2 I (Indeterminate) and 5 D (Difference of opinion). Eight of the 33 patients had significant coronary artery disease (CAD) and of these three were scored +ve (all triple vessel). Two patients without CAD were scored +ve. Eight subjects developed angina during exercise testing, of whom four had CAD, and four with CAD did no develop angina. Historically, 13 of the 33 subjects had typical angina, six having CAD; an additional eight had other significant chest pain, two having CAD. In these subjects with severe aortic valve disease, exercise testing and myocardial imaging with 201 TI was of little value in detecting CAD. All patients with CAD gave a history of significant chest pain.

Prazosin in the treatment of severe chronic congestive cardiac failure

The acute haemodynamic effects of prazosin 5 mg were investigated in 11 patients with severe chronic congestive cardiac failure. Six patients had their antifailure therapy discontinued while five continued on their usual medication. Two patients were exercised before and after prozosin. Following the drug, pulmonary capilary wedge pressure diminished 7 +/- 2(SE) mmHg (P < 0.005) and cardiac index increased 17 +/- 6% (P < 0.02). Mean arterial pressure fell in all subjects (- 9 +/- 2 mmHg; P < 0.001) and systemic vascular resistance was reduced in all but one (- 19 +/- 5%; P < 0.005). There was no significant change in heart rate. Four of the five subjects whose regular medications were continued were evaluated by clinical examination, chest X-ray, echocardiogram and treadmill stress test, before and after four weeks of prazosin therapy, one subject having died in this time. Two improved, one deteriorated and one remained unchanged. Thus, chronic prazosin therapy benefited individual patients but did not consistently provide long term improvement.

Comparison of vasodilator drug prazosin with digoxin in aortic regurgitation

Intravenous administration of the vasodilator sodium nitroprusside has beneficial haemodynamic effects in subjects with severe aortic regurgitation while acute digitalisation can produce unwanted effects associated with an increase in systemic vascular resistance. This study compares the haemodynamic effects of the vasodilator prazosin and digoxin in eight patients with isolated severe aortic regurgitation. Prazosin 5 mg orally resulted in a 12 +/- 3 (SE) per cent increase in cardiac index (thermodilution), maintained over four to six hours, while digoxin 0.75 mg intravenously did not change the cardiac index. Prazosin reduced mean arterial pressure by 9 +/- 3 mmHg and systemic vascular resistance by 18 +/- 4 per cent while digoxin resulted in a 6 +/- 2 per cent increase in the latter. Mean pulmonary capillary wedge pressure fell 3 mmHg with prazosin. In this group of patients with severe aortic regurgitation but without severe cardiac failure, the changes with either drug, studied in doses conventionally used, were small but those with prazosin were directionally more desirable than those resulting from digoxin.

Protein synthesis during right-ventricular hypertrophy after pulmonary-artery stenosis in the dog

The rate of protein synthesis in the heart of normal dogs and those with pulmonary-artery stenosis was measured by a continuous intravenous infusion of [14C]tyrosine. The protein-synthesis rate of both ventricles was the same in normal dogs and averaged 7.5% per day. The right ventricle hypertrophied rapidly after the acute imposition of pulmonary-artery stenosis, the wet weight increasing by 84% after 24 days, with the rate of increase being most rapid over the first 5 days. The left ventricle remained largely unaffected and served as an internal control. During hypertrophy there was an increased incorporation of [14C]tyrosine into protein without a significant change in the specific radioactivity of free tyrosine in the ventricles. After 5 days of stenosis the synthesis rate of the total mixed proteins of the right ventricle had increased to 13.6% per day, compared with 6.2% in the control left ventricle. This increase in synthesis was reflected in both the myofibrillar and sarcoplasmic proteins. After 5 days the protein-synthesis rate decreased, but still remained significantly elevated above that in the control left ventricle by 24 days of stenosis.

Myocardial ouabain content and susceptibility to ouabain cardiotoxicity associated with circulatory volume overload in the dog

The influence of circulatory volume overload on the myocardial uptake of ouabain and on cardiotoxicity was studied in the unanaesthetised dog with aorto-caval fistula. One hour after tritiated ouabain (0-02 mg/kg IV) both ventricles and atria contained more ouabain than did those of normal dogs (left ventricle (LV), 166+/-23 (SD) ng/g vs. 97+/-19 ng/g, P less than 0-001) while concentrations in skeletal muscle, liver, kidney and plasma were not different in the two groups. In other experiments ouabain was infused to cardiotoxicity (7-5 microgram/kg followed by 3 microgram/kg/min). Cardiotoxicity occurred earlier in dogs with fistula than in normals (16-5+/-2-7 min vs. 24-1+/-2-4 min, P less than 0-001). Ouabain concentrations in myocardium were not different (LV, 434+/-58 ng/g, vs. 442+/-42 ng/g) while concentrations in liver and kidney were less in those with fistula (181+/-35 ng/g vs. 278+/-69 ng/g, P less than 0-001; 1422+/-189 ng/g vs. 2747+/-479 ng/g, P less than 0-001). Average content of skeletal muscle was also less, in proportion to administered dose. The increment in myicardial ouabain content associated with aorto-caval fistula appears to be physiologically active and hence is presumably specifically bound to the digitalis receptor. The observations in this model suggest the possibility of augmented cardiac glycoside uptake in some clinical cardiac diseases.

Acceptability of a Whey-Based Quiescently Frozen Novelty

In one experiment, an observer panel of young people aged 6 to 14 years indicated no difference in preference for quiescently frozen novelties formulated with water or ones containing untreated cottage cheese whey as the entire formulation liquid. In another experiment, nine whey-based, orange flavored, novelties were evaluated by a panel of seven female and eight male children aged 10 to 12 years at triplicate sessions 2 to 4 days apart. Samples were coded differently at each session. Untreated cottage cheese whey supplied at the formulation liquid. Sucrose: dextrose (3.6:1) at total concentrations of 17, 23, or 29% and pH values of 3.2, 3.5, or 3.8 were evaluated on a 10-point degree of certainty scale from "like" to "do not like." Theory of signal detection (TSD) analysis shows that products with 23% total sweetener at pH 3.2 or 3.5 were rated equally acceptable. These products were rated significantly more preferable than the others. There were no significant differences in ratings made at each session or between individual panel members.

Influence of myocardial mechanical activity and coronary blood flow on myocardial digoxin uptake

The myocardial content of digoxin 60 min after intravenous administration in open-chest dogs correlated with heart rate controlled in individual dogs between 64 and 215 beats/min. In other dogs, increasing right ventricular mechanical work by constriction of the pulmonary artery resulted in greater right ventricular digoxin uptake. Increase in myocardial blood flow per se could not explain these findings since, in further dogs, increasing regional myocardial blood flow by adenosine infusion did not much affect digoxin uptake. Active uptake of cardiac glycosides is probably influenced by myocardial mechanical and metabolic activity.

Increase in myocardial digoxin content associated with circulatory volume overload in the dog

1. Tritiated (12alpha-3H) digoxin (0-05 mg/kg body weight) was administered intravenously to conscious dogs with circulatory volume overload induced by previous creation of aorto-caval fistulae. Dogs were killed after 5 min, 1, or 4 h, and the myocardium sampled. Digoxin was extracted and counted and results compared to those in normal dogs. 2. At each time, myocardial digoxin concentration of all cardiac chambers in test dogs was greater than normal. Plasma digoxin concentration measured 5 min after administration was greater in dogs with fistulae but the subsequent levels were not different. 3. Anaesthetized and open-chest dogs with fistulae studied 5 min after digoxin administration had greater myocardial concentrations than similarly studied normal dogs. Although myocardial concentrations of digoxin were higher in anaesthetized than in conscious dogs the group with fistulae had higher values than did the normal group, as was the case for unanaesthetized dogs. 4. The basis for the effect of fistula is probably multifactorial. Diminised peripheral blood flow and peripheral digoxin delivery and uptake, resulting initially in higher digoxin levels in plasma perfusing the myocardium, may play a role. Increased myocardial mechanical and metabolic activity almost certainly are important. Cardiac hypertrophy, cardiac failure per se and plasma electrolyte changes are probably not. 5. The results are consistent with previously demonstrated reduced digitalis tolerance in the dog with circulatory volume overload.