Homocysteine, a Risk Factor for Cardiovascular Disease

Fasting hyperhomocysteinemia is an independent risk factor for coronary artery disease, stroke, peripheral vascular atherosclerosis, and for arterial and venous thromboembolism. The risk for cardiovascular disease with homocysteine is similar to conventional risk factors. The interaction of hyperhomocysteinemia with hypertension and smoking is strong and the combined effect is more than multiplicative. The combined effect of homocysteine and cholesterol is additive. Homocysteine produces atherosclerosis, thromboembolism, and vascular endothelial cell injury. Vascular dysfunction produced by homocysteine may be due to endothelial cell damage. Homocysteinemia-induced atherosclerosis is probably due to various factors including endothelial cell injury, inability to sustain S-nitroso-homocysteine formation because of imbalance between production of nitric oxide by dysfunctional endothelium and homocysteine, smooth muscle cell proliferation, and thromboembolism. There is strong evidence that endothelial cell injury is associated with oxidative stress produced by homocysteine. Hyperhomocysteinemia is associated with numerous conditions, including coronary disease, stroke, peripheral vascular disease (carotid artery and cerebrovascular atherosclerosis), venous thrombosis, renal disease, diabetes mellitus, and organ transplant. Folic acid, vitamin B12 and B6 have been shown to be beneficial in reducing plasma homocysteine levels. Folic acid is specifically very effective, safe and inexpensive.

QT dispersion and risk factors for sudden cardiac death in patients with hypertrophic cardiomyopathy

This study examines the relation of QT dispersion (QTd) on a surface electrocardiogram (ECG) to clinical features and established risk factors of sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HC). One hundred fifty-six consecutive patients with HC (91 men, mean age 41+/-15 years, range 7 to 79) and 72 normal subjects (41 men, mean age 39+/-9 years, range 20 to 60) were studied. Standard 12-lead ECGs were recorded from each subject using a MAC VU electrocardiograph. Patients with nonsinus rhythm, atrioventricular conduction block, QRS duration > 120 ms, age < 15 years, and low amplitude T waves were excluded from the analysis (n=51). Another 22 patients who were receiving amiodarone and/or sotalol therapy were also excluded. QT interval and QTd were measured using automated analysis in the remaining 83 patients (46 men, age 40+/-14 years, range 16 to 76). QT interval (406+/-38 ms), QTc interval (432+/-27 ms), and QTd (43+/-25 ms) were significantly greater in patients with HC than in normal controls (386+/-31 ms, 404+/-16 ms, 26+/-16 ms, respectively) (p <0.0001). QTd was significantly greater in patients with HC with chest pain compared with asymptomatic or mildly symptomatic patients (50+/-28 ms vs 37+/-20 ms, p=0.02). Increased QTd was found in patients with dyspnea New York Heart Association functional classes II/III than in those with dyspnea New York Heart Association functional class I (50+/-27 ms vs 38+/-22 ms, p=0.04). QTd was weakly correlated with maximum left ventricular wall thickness (r=0.228, p=0.038). No significant association was found between QTd and any risk factors for SCD. Thus, patients with HC have increased QTd. The QTd correlates with symptomatic status. Assessment of QTd might provide complementary clinical characterization of patients with HC but its relation to SCD remains uncertain.

Formula method for stimulus setting in bilateral electroconvulsive therapy: relevance of age

Seizure thresholds were determined by titration in consecutive electroconvulsive therapy (ECT) patients at the first (n = 146) and sixth (N = 83) ECT sessions. Equations to predict the threshold at the first and sixth ECT were computed from these data using a stepwise linear regression model. These equations were tested prospectively at the first ECT (n = 48) and sixth ECT (n = 26) sessions. Stimulus dose derived from the corresponding equations yielded adequate seizure (successful) in 82% and 84% of patients, respectively. Predictions based on age alone (disregarding two other significant variables--illness severity and inion-nasion distance) were estimated at these two ECT sessions. This would not appreciably compromise the success rate. The "formula" method using age alone may therefore be used in routine clinical practice.

T wave complexity in patients with hypertrophic cardiomyopathy

The complexity of the T wave assessed by principal component analysis (PCA) has been proposed to reflect abnormal repolarization, which may be arrhythmogenic. To determine whether PCA can differentiate patients with hypertrophic cardiomyopathy (HCM) from normal subjects and whether PCA is of prognostic importance in HCM, 112 patients with HCM (41 +/- 14 years, 64 males) and 72 healthy subjects (39 +/- 9 years, 41 males) were studied. Patients with sinus node dysfunction, AV conduction block, flat T waves, QRS > 140 ms, and those < 15 years were excluded from this study. Standard 12-lead ECGs were recorded digitally using the MAC-VU system (Marquette Medical Systems). PCA parameters were computed using the QT Guard software package by Marquette. PCA ratio was significantly greater in HCM patients than in normal controls (23.9% +/- 12.4% vs 16.1% +/- 7.6%, P < 0.0001) and was correlated with QT-end dispersion (r = 0.24, P = 0.01) and QT peak (Q point to T peak) dispersion (r = 0.35, P < 0.0001). HCM patients with syncope (n = 23) had increased PCA ratios compared with those without syncope (29.1% +/- 11.5% vs 22.5% +/- 12.3%, P = 0.01). PCA ratio was similar in patients with and without nonsustained ventricular tachycardia on Holter (25.9% +/- 11.4% vs 22.7% +/- 12.1%, P = 0.2), as well as in patients treated with amiodarone or sotalol versus those not on therapy. In conclusion, assessment of the complexity of the T wave by PCA differentiates HCM patients from normal subjects. PCA ratio correlated with QT dispersion and an increased PCA ratio was associated with a history of syncope in HCM.

Initiating sequences in exercise induced idiopathic ventricular tachycardia of left bundle branch-like morphology

Initiating sequences for VT may infer the underlying arrhythmogenic mechanisms. This study examines the initiating sequences of exercise induced idiopathic VT of left bundle branch block-like (LBBB-like) morphology and makes an attempt to relate these to clinical aspects and the mechanisms of arrhythmia. Thirty-two patients (mean age 33.4 +/- 13.2 years; 18 men) with exercise induced VT in the absence of structural cardiac abnormality on history, clinical examination, and noninvasive and invasive investigations were divided into two groups on the basis of the initiating sequence of VT on exercise. Group I consisted of patients with long-short sequence of RR intervals prior to the onset of VT (initiating/preinitiating cycle length ratio < or = 0.78). Group II consisted of patients without changes in cycle length prior to VT. Group I mechanism would suggest delayed afterdepolarizations (DADs) or reentry whereas group II mechanism triggered activity due to early afterdepolarizations. Fourteen patients (group I) had long-short sequence and 18 patients (group II) were without cycle length changes prior to VT initiated during exercise. VT axis was inferior in all 18 patients in group II but only in 9 patients in group I (P = 0.02). In these predefined patient groups, sustained monomorphic VT could not be initiated by programmed stimulation in any patient in group I, whereas four patients in group II had inducible VT. Patients in group II also had higher incidence of sustained VT on ambulatory monitoring (P < 0.05). The two groups did not differ in other respects. This study demonstrates the existence of at least two possible mechanisms of initiation of exercise induced idiopathic VT of LBBB-like morphology. VT initiated without cycle length changes is more common, more likely to have an inferior axis suggesting an outflow tract origin, and is probably related to triggered activity secondary to DADs. VT initiated with a long-short sequence is more often nonsustained and may have a superior axis suggesting an origin from the body or septal region of the ventricle. The two groups, therefore, exhibit differences in electrophysiological characteristics that may aid classification and therapy of this arrhythmia.

Oxygen Free Radicals and Endotoxic Shock: Effect of Flaxseed

BACKGROUND: Cardiac dysfunction and tissue injury during endotoxemia may be caused by increased levels of oxygen free radicals. METHODS AND RESULTS: We therefore investigated the effects of endotoxic shock on cardiac function and contractility, plasma creatine kinase (CK) activity and lactate concentration, oxyradical-producing activity of polymorphonuclear leukocytes (PMNL-CL) and white blood corpuscles, antioxidant reserve (cardiac chemiluminescence [LV-CL]), antioxidant enzyme activity (superoxide dismutase, catalase, glutathione peroxidase), cardiac malondialdehyde (MDA) concentration, a lipid peroxidation product, and hemodynamics in the absence or presence of flaxseed treatment in anesthetized dogs. Flaxseed contains lignans that have antioxidant activites and inhibit platelet-activating factor (PAF). The dogs were assigned to three groups: group I, sham control; group II, endotoxin (ET) treated (5 mg/kg intravenously); group III, ET + flaxseed (2 gm/kg/day orally) for 6 days. ET produced a decrease in cardiac function and contractility and antioxidant enzyme levels, and an increase in cardiac MDA and LV-CL, PMNL-CL, and plasma CK and lactate. Pretreatment with flaxseed attenuated the ET-induced cardiac dysfunction and cellular damage. Protection was incomplete for cardiovascular function, plasma CK, and lactate. CONCLUSIONS: These results suggest that oxyradicals and/or PAF may be involved in the deterioration of cardiovascular function and cellular integrity during ET shock and that antioxidant and anti-PAF agents may be effective in the treatment of ET shock.

Clinical predictors of seizure threshold in bilateral ect

Research on determinants of ECT seizure threshold is inadequate. In view of differences in ECT populations and confounding factors, there is a need for examining this in our population. Consecutive consenting inpatients (N=100), referred for bilateral (BL) ECT by treating psychiatrists at National Institute of Mental Health and Neuro Sciences Hospital, Bangalore, formed the sample for the study. Thiopentone, succinylcholine and atropine were used for modification. Seizure threshold (dependent variable) was determined by titration method at the first ECT. The independent variables were age, gender, diagnosis, illness severity (Clinical Global Impression; CGI), concurrent drugs, head circumference (HC) and inion-nasion distance (IND). Age, IND and CGI severity predicted seizure threshold in forward, stepwise, linear regression model.

Probing the phosphoinositide binding site of the clathrin assembly protein AP-2 with photoaffinity labels

The relative binding specificities of the subunitsof bovine assembly protein AP-2 for the phosphatidylinositol polyphosphates (PtdInsPn) and inositol polyphosphates (InsPn) were determined by photoaffinitylabeling. Three types of benzophenone-containing photoprobes were employed: (i) the water-solubleP-1- or P-2-tethered p-benzoyldihydrocinnamoyl-InsPn (BZDC-InsPn) analogs, (ii) P-1-linked phosphotriester PtdInsPn analogs that sampled the interface between the water and lipid phases, and (iii) sn-1-O-acyl-linked PtdInsPn analogs that interacted with proteins penetrating the bilayer. The InsPn and PtdInsPn probes bind with highest selectivity and affinity to the two alpha subunit isoforms, with certain probes and conditions resulting in strong labeling of the 50-kDa mu subunit. Three main conclusions were reached: (i) head group recognition predominated over acyl chain recognition, (ii) the PtdInsPn binding site of alpha-AP-2 prefers more highly phosphorylated species, and (iii) the protein-acyl chain interactions showed high capacity but low selectivity.

Fumarate modulates bacterial flagellar rotation by lowering the free energy difference between the clockwise and counterclockwise states of the motor

Switching flagellar rotation from one direction to another is an essential part of bacterial chemotaxis. Fumarate has been shown to possess the capacity to restore to flagella of cytoplasm-free, CheY-containing bacterial envelopes the ability to switch directions and to increase the probability of reversal in intact cells. Neither the target of fumarate action nor the mechanism of function is known. To distinguish between the two potential targets of fumarate, the response regulator CheY and the flagellar switch-motor complex, we compared flagellar rotation between isogenic strains that lacked CheY and had either low or high levels of fumarate. The difference in the fumarate levels was due to a deletion of the genes encoding the enzymes that synthesize and metabolize fumarate; succinate dehydrogenase and fumarase, respectively. The strains were in a gutted background (i.e. a background deleted for the cytoplasmic chemotaxis proteins and some of the receptors), and switching was achieved by carrying out the measurements at 2.5 degreesC, where it has been demonstrated that gutted cells switch spontaneously. The flagellar rotation of the strain with the highest level of fumarate was the most clockwise-biased and had the highest reversal frequency, indicating that fumarate is effective even in the absence of CheY. Fumarate reduced the free energy difference of the counterclockwise-to-clockwise transition and had no appreciable effect on the activation energy of this transition. Similar observations were made at room temperature, provided that intracellular CheY was present. In a wild-type background, both mutants made rings on semi-solid agar typical of normal chemotaxis. Taken together, the results suggest that the target of fumarate is the switch-motor complex, that fumarate acts by increasing the probability of the clockwise state, and that a fumarate level as low as that found in succinate dehydrogenase mutants is sufficient for normal chemotaxis.

Increased oxidative stress in rat liver and pancreas during progression of streptozotocin-induced diabetes

1. Oxygen free radicals have been suggested to be a contributory factor in complications of diabetes mellitus. There are many reports indicating the changes in parameters of oxidative stress in diabetes mellitus. In this study we aimed to identify whether oxidative stress occurs in the liver and pancreas in the initial stages of development of diabetes. 2. We therefore investigated the lipid peroxide level (thiobarbituric acid-reactive substances, TBARS) and activities of antioxidant enzymes [superoxide dismutase (SOD), catalase and glutathione peroxidase] in liver and pancreas of control and streptozotocin-induced diabetic rats at various stages of development of diabetes. 3. Male Sprague-Dawley rats were divided into two groups: group I, control (n = 42) and group II, diabetic (n = 42). Each group was further subdivided into seven groups consisting of six rats each. Rats in these subgroups were studied at weekly intervals (0 to 6 weeks). Plasma glucose levels, TBARS levels and activities of antioxidant enzymes were measured in liver and pancreas at various time intervals. 4. There was a significant (P < 0.05) and progressive increase in TBARS levels of liver and pancreas in the diabetic group. Total SOD and Cu-Zn-SOD activity increased (P < 0.05) with progression of diabetes while Mn-SOD activity showed no significant change in either tissue. Catalase and glutathione peroxidase activities increased significantly (P < 0.05) in liver and pancreas. 5. Immunohistochemical study of pancreatic islet revealed a decrease in the expression of insulin with progression of diabetes. However, glucagon and somatostatin showed an increase in immunoreactivity and a difference in their distribution pattern. 6. The findings of the present study suggest that oxidative stress starts at early onset of diabetes mellitus and increases progressively. In conclusion, the structural damage to these tissues or complications of diabetes mellitus may be due to oxidative stress.

Acute post-ECT cardiovascular response: a comparison of threshold right unilateral and bilateral ECT

The effect of electrode placement on cardiovascular responses was studied. Rate pressure product and diastolic blood pressure before anesthesia and 30 s after electroconvulsive therapy (ECT) seizure were recorded. Recordings were made at the first (threshold ECT) session in 124 bilateral ECT (BLECT) and 95 unilateral ECT (ULECT) consenting patients. Postictal rate pressure product (RPP) was significantly higher after BLECT than ULECT. Mean increase in RPP from pre- to postictal phase was 31% in the former. The corresponding change with ULECT (20%) was significantly smaller. In the stepwise, multiple regression model, pre-ECT RPP, age, and stimulus laterality significantly contributed to postictal RPP. No cardiovascular complications occurred in any of the 219 ECT sessions.

Sudden death in hypertrophic cardiomyopathy: potential importance of altered autonomic control of vasculature

Current evidence suggests that alterations in the autonomic function and abnormal vascular control play a significant role either as independent triggers themselves or as modifiers of ischaemia and tolerance to to arrhythmias. A combination of several factors--that is, arrhythmia, hypotension, altered autonomic function including vascular control, and ischaemia are therefore likely to act as triggers for sudden death. The relative contribution of each of these factors needs further detailed study.

Dipyridamole stress thallium-201 perfusion abnormalities in patients with hypertrophic cardiomyopathy. Relationship to clinical presentation and outcome

AIMS

Thallium-201 perfusion abnormalities are common in patients with hypertrophic cardiomyopathy and may be associated with an adverse prognosis in the young. The aim of this study was to prospectively determine the relationship between thallium-201 defects during dipyridamole stress to clinical presentation and outcome in a large consecutive series of patients with hypertrophic cardiomyopathy.

METHODS/RESULTS

Thallium-201 single photon computed tomography was performed in 216 patients with hypertrophic cardiomyopathy during dipyridamole stress (0.5 mg. kg-1). Fixed perfusion defects occurred in 25%, and reversible defects in 22%. A combination of defects was present in 7%. Fixed defects were associated with: a history of syncope (17 of 46 with, vs 36 of 170 without syncope, P = 0.03); larger left ventricular end-diastolic (46.9 +/- 7.4 mm vs 43.3 +/- 6.4 mm; P = 0.001) and end-systolic dimension (30.2 +/- 8.4 mm vs 24.5 +/- 5.9 mm, P < 0.0001); increased left atrial diameter (46.1 +/- 8.1 mm vs 40.5 +/- 7.7 mm, P < 0.0001); lower fractional shortening (35.9 +/- 10.4% vs 43.8 +/- 8.6%, P < 0.0001): and lower maximal exercise oxygen consumption (24.2 +/- 8.1 ml. min-1. kg-1 vs 29.4 +/- 8.8 ml. min-1. kg-1, P < 0.0003). Reversible defects did not correlate with symptomatic status, but were associated with: larger left atrial dimensions (44.5 +/- 8.1 mm vs 41.0 +/- 8.0 mm; P = 0.009) and greater maximal left ventricular wall thickness (24.0 +/- 7.0 mm vs 20.6 +/- 7.0 mm, P = 0.003). The mean follow up time was 41 +/- 21 months, range 0.6-124. There was no association between any thallium-201 abnormality and disease related death in young or adult patients.

CONCLUSION

The present study shows that fixed thallium-201 perfusion defects detected during dipyridamole stress in patients with hypertrophic cardiomyopathy are associated with syncope, larger left ventricular cavity dimensions and reduced exercise capacity. Although the event rate was relatively small, there was no evidence for an association between thallium-201 defects and survival.

Comparison of the three strategies of verbal scoring of the Glasgow Coma Scale in patients with stroke

Presence of aphasia in patients with stroke poses a problem in the use of the full form (eye-motor-verbal) Glasgow Coma Scale (GCS). Stroke investigators and clinicians have used three different strategies to deal with the untestable verbal subscale, i.e. eliminating the verbal subscale; pseudoscoring with 'one', and median value substitution; but the predictive accuracy of the strategies has not been compared. To compare the predictive accuracy of the three strategies for acute mortality in stroke, we prospectively applied the GCS to 275 consecutive patients with acute stroke and recorded their survival status before discharge from hospital. 95 (33.8%) patients died. 32 (12%) patients had untestable verbal score. Receiver-Operator-Characteristic curves for predicting mortality were constructed with the GCS sum score and with the multivariate logistic models, and areas under the curves were measured to compare the predictive accuracy. They were all found to be similar (0.87-0.88 sq unit). Specifically, the GCS with eye and motor subscale had 87% accuracy compared to 88% for the model with eye, motor and verbal scale. We conclude that the short-form (eye-motor) GCS is as good a predictor of early mortality (within 2 weeks) as the full form (eye-motor-verbal) GCS in patients with stroke.

Reduction of hypercholesterolemic atherosclerosis by CDC-flaxseed with very low alpha-linolenic acid

Flaxseed (Type I flaxseed) with 51-55% alpha-linolenic acid in its oil and richest source of plant lignans, has been shown to reduce hypercholesterolemic atherosclerosis by 46% without lowering serum lipids. Antiatherogenic activity was claimed to be due to its alpha-linolenic acid and/or lignan content. If alpha-linolenic acid component of flaxseed is responsible for antiatherogenic activity, then, CDC-flaxseed (Type II flaxseed) which has similar oil and lignan content but has very little (2-3% of the total oil) alpha-linolenic acid would have no antiatherogenic effect. An investigation, therefore, was made of Type II flaxseed on high cholesterol diet-induced atherosclerosis and serum lipids [total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C)] in rabbits. Rabbits were assigned to four groups: Group I, Control; Group II, Type II flaxseed diet (7.5 g/kg orally daily); Group III, 1% cholesterol diet; Group IV, 1% cholesterol diet supplemented with Type II flaxseed (7.5 g/kg orally daily). Blood samples were collected before (0 time) and after 4 and 8 weeks of experimental diets for measurement of serum lipids. Aorta was removed at the end of 8 weeks for assessment of atherosclerotic plaques. Serum TC, LDL-C, TC/HDL-C, and LDL-C/HDL-C were lower in Group IV as compared to Group III by 14 and 31%, 17 and 32%, 28 and 34% and 24 and 32%, respectively, at 4 and 8 weeks. HDL-C was not affected by Type II flaxseed in hypercholesterolemic rabbit. TG and VLDL-C were markedly increased in Group IV as compared to Group III. Type II flaxseed reduced the development of atherosclerosis by 69%. Histological changes in the atherosclerotic regions were qualitatively similar in Groups III and IV. Results indicate that reduction in hypercholesterolemic atherosclerosis by Type II flaxseed is due to a decrease in serum TC and LDL-C. In conclusion, antiatherogenic activity of Type II flaxseed is not due to alpha-linolenic acid.

Prospective prognostic assessment of blood pressure response during exercise in patients with hypertrophic cardiomyopathy

BACKGROUND

Previous studies revealed that an abnormal blood pressure response (ABPR) during exercise was common in young hypertrophic cardiomyopathy (HCM) patients and was associated with a family history of premature sudden cardiac death (SCD). This study was performed prospectively to assess the prognostic significance of blood pressure response during exercise in young patients with HCM.

METHODS AND RESULTS

Maximum symptom-limited treadmill exercise testing with continuous blood pressure monitoring was performed in 161 consecutive patients 8 to 40 years old (27+/-9). A normal blood pressure response, defined as an increase in the systolic pressure of at least 20 mm Hg from rest to peak exercise in the absence of a fall of >20 mm Hg from peak pressure, was seen in 101 (63%). In 60 (37%), the blood pressure response was abnormal. There was no significant difference in patients with normal blood pressure response and ABPR in terms of age, sex, follow-up, or recognized risk factors for SCD. During the follow-up period (mean, 44+/-20 months), SCD occurred in 12 patients: 3 (3%) in the normal blood pressure response group versus 9 (15%) in the ABPR group (P<.009). ABPR had a sensitivity of 75%, a specificity of 66%, a negative predictive value of 97%, and a positive predictive value of 15% for the prediction of SCD. There was no significant difference in the incidence of other recognized risk factors between patients with SCD and the survivors.

CONCLUSIONS

A normal exercise blood pressure response identifies low-risk young patients with HCM. An ABPR identifies the high-risk cohort; the low positive predictive accuracy, however, indicates that further risk stratification is warranted.

Cardiac depression and cellular injury in hemorrhagic shock and reinfusion: role of free radicals

We investigated the effect of hemorrhagic shock and reinfusion on the cardiac function and contractility, plasma CK and CK-MB activity and lactate concentration, oxyradical-producing activity of polymorphonuclear leukocytes (PMNL-CL), cardiac chemiluminescence (LV-CL), antioxidant enzyme activity [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-PX)] and malondialdehyde (MDA) concentration in anesthetized dogs to determine the role of oxyradicals in cardiac depression and cellular injury in hemorrhagic shock and reinfusion. The dogs were assigned into three groups: I (sham), 4 h duration; II (S + R), 2 h of shock followed by reinfusion for 2 h; III (SOD + S + R), as II but pretreated with PEG-SOD. Hemorrhagic shock was produced by withdrawal of blood to maintain the mean arterial pressure at 50 +/- 5 mm Hg. Cardiac function and contractility were depressed during hemorrhagic shock. Plasma CK, CK-MB and lactate increased during shock. Following reinfusion after 2 h of shock hemodynamic parameters and plasma lactate tended to return towards control values. Plasma CK and CK-MB, PMNL-CL and cardiac MDA, total-, Mn- and CuZn-SOD activity increased while LV-CL decreased. In spite of the increase in the antioxidant reserve, there was oxidative damage. Pretreatment with SOD attenuated the deleterious effects of shock and reinfusion on the cardiovascular function, plasma CK, and CK-MB, PMNL-CL, cardiac MDA, SOD, and LV-CL. Protection was incomplete for cardiovascular function and plasma CK and CK-MB. These results suggest that oxyradicals may partly be involved in the deterioration of cardiovascular function and cellular injury during hemorrhagic shock and reinfusion.