Smoking Accelerates Atrioventricular Conduction in Humans Concordant with Increased Dopamine Release

Smoking is associated with cardiac arrhythmia, stroke, heart failure, and sudden cardiac arrest, all of which may derive from increased sympathetic influence on cardiac conduction system and altered ventricular repolarization. However, knowledge of the effects of smoking on supraventricular conduction, and the role of the sympathetic nervous system in them, remains incomplete. Participants with intermediate-high cardiovascular disease risk were measured for urinary catecholamines and cotinine, and 12-lead electrocardiograms (ECGs) were measured for atrial and atrioventricular conduction times, including P duration, PR interval, and PR segment (lead II), which were analyzed for associations with cotinine by generalized linear models. Statistical mediation analyses were then used to test whether any significant associations between cotinine and atrioventricular conduction were mediated by catecholamines. ECG endpoints and urinary metabolites were included from a total of 136 participants in sinus rhythm. Atrial and atrioventricular conduction did not significantly differ between smokers (n = 53) and non-smokers (n = 83). Unadjusted and model-adjusted linear regressions revealed cotinine significantly and inversely associated with PR interval and PR segment, but not P duration. Dopamine, norepinephrine, and epinephrine all inversely associated with PR interval, whereas only dopamine was also inversely associated with PR segment (p < 0.05). Dopamine and norepinephrine (but not epinephrine) also associated positively with cotinine. Dopamine mediated the relationship between cotinine and PR interval, as well as the relationship between cotinine and PR segment. Smoking is associated with accelerated atrioventricular conduction and elevated urinary dopamine and norepinephrine. Smoking may accelerate atrioventricular nodal conduction via increased dopamine production.

Inhalation of printer-emitted particles impairs cardiac conduction, hemodynamics, and autonomic regulation and induces arrhythmia and electrical remodeling in rats

BACKGROUND

Using engineered nanomaterial-based toners, laser printers generate aerosols with alarming levels of nanoparticles that bear high bioactivity and potential health risks. Yet, the cardiac impacts of printer-emitted particles (PEPs) are unknown. Inhalation of particulate matter (PM) promotes cardiovascular morbidity and mortality, and ultra-fine particulates (< 0.1 μm aerodynamic diameter) may bear toxicity unique from larger particles. Toxicological studies suggest that PM impairs left ventricular (LV) performance; however, such investigations have heretofore required animal restraint, anesthesia, or ex vivo preparations that can confound physiologic endpoints and/or prohibit LV mechanical assessments during exposure. To assess the acute and chronic effects of PEPs on cardiac physiology, male Sprague Dawley rats were exposed to PEPs (21 days, 5 h/day) while monitoring LV pressure (LVP) and electrocardiogram (ECG) via conscious telemetry, analyzing LVP and heart rate variability (HRV) in four-day increments from exposure days 1 to 21, as well as ECG and baroreflex sensitivity. At 2, 35, and 70 days after PEPs exposure ceased, rats received stress tests.

RESULTS

On day 21 of exposure, PEPs significantly (P < 0.05 vs. Air) increased LV end systolic pressure (LVESP, + 18 mmHg) and rate-pressure-product (+ 19%), and decreased HRV indicating sympathetic dominance (root means squared of successive differences [RMSSD], - 21%). Overall, PEPs decreased LV ejection time (- 9%), relaxation time (- 3%), tau (- 5%), RMSSD (- 21%), and P-wave duration (- 9%). PEPs increased QTc interval (+ 5%) and low:high frequency HRV (+ 24%; all P < 0.05 vs. Air), while tending to decrease baroreflex sensitivity and contractility index (- 15% and - 3%, P < 0.10 vs. Air). Relative to Air, at both 2 and 35 days after PEPs, ventricular arrhythmias increased, and at 70 days post-exposure LVESP increased. PEPs impaired ventricular repolarization at 2 and 35 days post-exposure, but only during stress tests. At 72 days post-exposure, PEPs increased urinary dopamine 5-fold and protein expression of ventricular repolarizing channels, Kv1.5, Kv4.2, and Kv7.1, by 50%.

CONCLUSIONS

Our findings suggest exposure to PEPs increases cardiovascular risk by augmenting sympathetic influence, impairing ventricular performance and repolarization, and inducing hypertension and arrhythmia. PEPs may present significant health risks through adverse cardiovascular effects, especially in occupational settings, among susceptible individuals, and with long-term exposure.

Magnesium supplementation: Pharmacokinetics in cardiac surgery patients with normal renal function

BACKGROUND

Intravenous magnesium is routinely administered in intensive care units (ICU) to treat arrhythmias after cardiothoracic surgery. There are no data on the pharmacokinetics of continuous magnesium infusion therapy.

OBJECTIVE

To investigate the pharmacokinetics of continuous magnesium infusion, focusing on serum and urinary magnesium concentration, volume of distribution and half-life.

METHODS

We administered a 10 mmol bolus of magnesium-sulfate followed by a continuous infusion of 3 mmol/h for 12 h in twenty cardiac surgery patients. We obtained blood and urine samples prior to magnesium administration and after one, six, and 12 h.

RESULTS

Median magnesium levels increased from 1.09 (IQR 1.00-1.23) mmol/L to 1.59 (1.45-1.76) mmol/L after 60 min (p < .001), followed by 1.53 (1.48-1.71) and 1.59 (1.48-1.76) mmol/L after 6 and 12 h. Urinary magnesium concentration increased from 9.2 (5.0-13.9) mmol/L to 17 (13.6-21.6) mmol/L after 60 min (p < .001). Cumulative urinary magnesium excretion was 28 mmol (60.9% of the dose given). The volume of distribution was 0.25 (0.22-0.30) L/kg. There were no episodes of severe hypermagnesemia (≥3 mmol/L).

CONCLUSION

Combined bolus and continuous magnesium infusion therapy leads to a significant and stable increase in magnesium serum concentration despite increased renal excretion and redistribution.

The dose-response decrease in heart rate variability: any association with the metabolites of polycyclic aromatic hydrocarbons in coke oven workers?

Background

Air pollution has been associated with an increased risk of cardiopulmonary mortality and decreased heart rate variability (HRV). However, it is unclear whether coke oven emissions (COEs) and polycyclic aromatic hydrocarbons (PAHs) are associated with HRV.

Objectives

Our goal in the present study was to investigate the association of exposure to COEs and the urinary metabolite profiles of PAHs with HRV of coke oven workers.

Methods

We measured benzene soluble matter, carbon monoxide, sulfur dioxide, particulate matters, and PAHs at different workplaces of a coke oven plant. We determined 10 urinary PAH metabolites and HRV indices of 1333 workers using gas chromatography–mass spectrometry and a 3-channel digital Holter monitor, respectively.

Results

Our results showed that there was a significant COEs-related dose-dependent decrease in HRV, and an inverse relationship between the quartiles of urinary 2-hydroxynaphthalene and five HRV indices (p_trend<0.01 for all). After adjustment for potential confounders, elevation per interquartile range (IQR) (1.81 µg/mmol creatinine) of urinary 2-hydroxynaphthalene was associated with a 5.46% (95% CI, 2.50–8.32) decrease in standard deviation of NN intervals (SDNN). As workers worked more years, SDNN gradually declined in the same quartiles of 2-hydroxynaphthalene levels (p_trend = 1.40×10⁻⁴), especially in workers with the highest levels of 2-hydroxynaphthalene.

Conclusions

Occupational exposure to COEs is associated with a dose-response decrease in HRV. In particular, increased exposure to 2-hydroxynaphthalene is associated with significantly decreased HRV. Increase of working years and exposure levels has resulted in a gradual decline of HRV.

Ventricular arrhythmias late after myocardial infarction are related to hypomagnesemia and magnesium loss: preliminary trial of corrective therapy

It has been well established that in acute myocardial infarction (MI) many patients display low serum magnesium (Mg). This is associated with complex ventricular arrhythmias. The question arises whether predischarge arrhythmias occurring late after MI might also be related to Mg imbalance. In 118 patients subjected to heart rhythm 24 h Holter monitoring in the second or third week after MI, we investigated (1) the relationship between serum Mg, urinary Mg loss, and ventricular arrhythmias, and (2) the effect of Mg supplementation on heart rhythm disturbances. In patients with undisturbed rhythm or monomorphic ventricular ectopic beats (VEB) (Lown 0-2; n = 84), mean serum Mg level (mg% +/- SD) was 1.83 +/- 0.21, whereas in patients with multifocal VEB, pairs, or nonsustained ventricular tachycardia (VT) (Lown 3-4; n = 34) serum Mg was decreased to 1.68 +/- 0.27 (p < 0.01). Serum Mg normal range in our laboratory is 1.7-2.6 mg%. The lowest serum Mg reaching 1.55 +/- 0.27 was found in nonsustained VT (Lown 4 b) subgroup (n = 14). Urinary Mg loss measured in 81 patients was more pronounced in those with Lown 3-4 arrhythmias (n = 26) than with Lown 0-2 (n = 55). The daily values were 73 +/- 22 and 54.4 +/- 26 mg, respectively (p < 0.001). Thirteen patients with complex arrhythmias and low serum Mg received Mg supplementation (MgSO4, 8 g in 500 ml 5% glucose intravenously during 24 h). This resulted in restoration of almost undisturbed rhythm in 10 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Heart rates, cardiac arrhythmia, lactate levels and catecholamine excretions in CHD patients during cross-country skiing

We examined cross-country skiing-related strain in 10 less experienced postinfarction patients, performing a skiing test, covering a distance of approximately 7 km in 90 min. Heart rates, cardiac arrhythmia, lactic acid levels and catecholamine excretions were determined as strain indicators. The patients' exercise capacity, estimated during graded ergometric cycling, was 2.1 +/- 0.4 watts.kg-1, indicating a nearly age-appropriate submaximum performance ability. They had suffered myocardial infarction 2.8 +/- 0.7 years previously, participated regularly in a rehabilitation program for at least one year, and they did not show coronary insufficiency or significant cardiac dysrhythmias during laboratory testing under their usual medications. They went cross-country skiing during a 4-day instruction period and subsequently performed a cross-country skiing test on the 5th day. Mean skiing-related heart rates (124 +/- 9 bpm) and adrenaline excretions (124 +/- 88 pmol.min-1) corresponded on average to an exercise level of 1.85-2.0 watts.kg-1 during laboratory testing, and mean noradrenaline excretions (586-343 pmol.kg-1) and lactate concentrations (3.83 +/- 2.18 mmol.l-1) to a level of 1.48-1.73 watts.kg-1. Cardiac dysrhythmias were observed in a moderate number of 6-8 SVES, 9 to 12 VES and 4 to 7 couplets of VES per 1000 beats during cross-country skiing. The present results point to a comparatively high cardiovascular strain in less experienced postinfarction patients during a cross-country skiing test at an intensity level thought to be moderate.

Iodine intake in an urban environment: a study of urine iodide excretion in Auckland

Dietary iodine intake was estimated by measurement of iodide in random overnight 12 hr and 24 hr urine samples. Urinary iodide excretion was measured in 231 healthy females comprising 127 female secondary students (ages 16-19), 27 female tertiary students (17-23 yr), 42 female laundry workers (18-52 yr) and 26 pregnant women in the third trimester (18-40 yr). Urine iodide excretion was also examined in a group of 28 patients attending a thyroid clinic, with thyroid disease of diverse aetiology and in 34 patients taking the antiarrhythmic drug amiodarone for control of cardiac arrhythmias. The mean daily urine iodide excretion was 2.4 mumol/day (0.9-5.8 mumol/day) and iodide to creatinine ratio 0.21 mumol/mmol (0.09-0.29). Iodine deficiency (less than 0.4 mumol/day) was not observed in any subject. Excessive iodine (greater than 8 mumol/day) was found only in patients known to be taking iodine-containing drugs and in one normal individual. The urine iodide was normal in 154 female students, 14 of whom had a trivial thyroid enlargement. The study suggests that dietary sources other than iodised salt contribute significantly to dietary iodine intake and that residual goitre in the community is not secondary to deficiency or excess of dietary iodine.

[Detection of aprindine and its metabolites in plasma and urine]

In 36 patients with cardiac arrhythmias (predominantly ventricular premature beats), who were on oral aprindine long-term therapy with 50 to 400 mg daily, plasma levels were measured by gas chromatography after 3.5 hours of the last administration. There was a general dependency of plasma levels on the given dose, however, with considerable overlapping in individual values. In 24 patients the arrhythmias ceased, in six patients there was a clear, in two a moderate improvement. There was no clear therapeutic effect in four patients who were treated with a daily dose of 50 and 100 mg, respectively. Among the 36 patients, three who had plasma levels exceeding 2 micrograms/ml developed tremor and dizziness. After dose-reduction these side effects disappeared. The present results suggest that therapeutic plasma levels of aprindine are in the range of 1.0 to 1.75 micrograms/ml. A plasma level of 2 micrograms/ml should not be exceeded because of the possibility of side-effects. In six healthy males time-concentration curves of aprindine and its metabolites in plasma and urine were measured by gas chromatography. From the results a two-compartment model may be applied, the half-life of elimination was calculated to be 37 hours (plasma) and 31 hours (urine). With respect to the metabolites, in plasma only des-ethyl-aprindine (DEAP), in urine DEAP, hydroxy-, des-phenyl- and des-indanyl-aprindine could be found. Unlike aprindine, the DEAP-concentration curve in plasma showed a very slight decrease until the end of the 96-hour period of determination.

Cardiovascular complications due to pheniramine overdosage

Cardiovascular toxicity including ventricular extrasystoles associated with pheniramine overdosage has been documented in the absence of factors recognised to aggravate this toxicity. The presence of pheniramine and the absence of other compounds was established using analytical techniques. It is concluded that patients with pheniramine overdosage should be treated exercising the same precautions as with tricyclic overdosage. Several sudden and unexpected deaths have occurred due to pheniramine overdosage in both adults and children. The cause of death in each case was not known. The purpose of this report is to document clinical features of pheniramine overdosage, in particular previously unsuspected cardiovascular toxicity manifesting as clinically significant ventricular arrhythmias. Pheniramine was positively identified in the overdosed patient, and the presence of other agents excluded.

Effects of long-term treatment with procaine amide. A prospective study with special regard to ANF and SLE in fast and slow acetylators

During 1970-75 a total of 42 patients have been subjected to long-term treatment with procaine amide (PrA) because of different cardiac arrhythmias and have been observed up to over 5 years. Among these patients 35 (83%) developed a significantly increased titer of ANF and of these, 12 patients (29%) developed a "classical" drug-induced SLE syndrome. In the SLE group all but 2 improved rapidly after cessation of PrA, and the ANF titer decreased continuously but slowly in both groups. Acetylation test with sulphamidine and/or isoniazid in 11 patients among the SLE cases showed 8 slow and 3 fast acetylators. Among 12 patients who also had received PrA for a long time, but had not shown any signs of an SLE syndrome, there were 10 fast and 2 slow acetylators.

Cardiac arrhythmias, electrolytes, and digoxin concentration in plasma and urine in patients treated with digoxin

Cardiac arrhythmias, digoxin concentration in plasma and urine, digoxin and creatine clearances, electrolytes in plasma and in erythrocytes, and subjective symptoms have been carefully studied for 5 consecutive days in 19 patients with definite or suspected digitalis intoxication. The digoxin treatment was discontinued during the observation period. Eleven controls without any signs of toxicity were similarly followed on unchanged maintenance dosage. All patients were independently classified as toxic or non-toxic from the follow-up of extended ECG recordings and subjective symptoms. In 9 definitely toxic patients a plasma digoxin concentration 3.1 plus or minus 0.7 ng/ml was found, as compared to 1.4 plus or minus 0.5 ng/ml for the 11 controls. In the suspect toxic group 1.5-3.9 ng/ml was found. The high digoxin level in the toxic group corresponds to a low digoxin clearance. In the toxic patients cardiac arrhythmias were related in most cases to a plasma digoxin level above 2.5 ng/ml and usually disappeared when the concentration had decreased below this. Suspect toxic patients, classified as probably non-toxic, and controls had with two exceptions plasma digoxin levels below 2 ng/ml. It is suggested that digitalis toxicity should be considered at a plasma digoxin concentration above 2 ng/ml. It must be stressed that this limit is not absolute and is affected by, among other things, a disturbance of intra- and extracellular electrolytes.

Shortening of electromechanical systole as a manifestation of excessive adrenergic stimulation in acute myocardial infarction

The relationship between shortened electromechanical systole (QS 2 I) and 24-hour urinary catecholamine excretion (E+NE) was studied in 51 patients admitted to the coronary care unit with suspected acute myocardial infarction. Among these patients, 24 had a documented acute myocardial infarction while 27 had chest pain without evidence of recent myocardial infarction. Patients receiving cardioactive drugs or with impaired renal function were excluded. Initial elevation of catecholamine excretion was found in 22 of 24 subjects with myocardial infarction and 14 patients without documented myocardial infarction. A close linear correlation (r = -0.82, P < 0.001) was noted between shortening of the QS 2 I and catecholamine excretion among all patients irrespective of the presence of documented infarction. Patients with serious arrhythmias had significantly higher levels of catecholamine excretion. In 13 patients with a short QS 2 I, 2.5 mg of propranolol given intravenously produced a significant lengthening of the QS 2 I while no change in the QS 2 I occurred in normal controls. This test provided useful corroborative evidence that the short QS 2 I was related to excessive adrenergic stimulation. In view of the current availability of effective beta-adrenergic blocking agents, these results may improve the selection of patients for antiarrhythmic therapy with these drugs.

Changes in systolic time intervals in acute myocardial infarction

After acute myocardial infarction there is a shortening of the QS2 interval and the ejection time. The pre-ejection time is either normal or prolonged. After the stage of maximum shortening of the QS2 interval and ejection time, there is a progressive improvement towards the normal. In this study there was no correlation between the shortened QS2 interval and ejection time, and the level of urinary catecholamine excretion. The physiological and clinical significance of these changes in the systolic time intervals and their relation to the altered haemodynamics and mechanics are discussed.