Traffic related pollution and heart rate variability in a panel of elderly subjects.

BACKGROUND: Particulate air pollution has been associated with increased cardiovascular deaths and hospital admissions. To help understand the mechanisms, the types of particles most involved, and the types of persons most susceptible, the association between exposure to summertime air pollution and heart rate variability (HRV) was examined in a panel study of 28 elderly subjects. METHODS: Subjects were seen once a week for up to 12 weeks and HRV (SDNN, r-MSSD, PNN50, low frequency/high frequency ratio (LFHFR)) was measured for approximately 30 minutes at each session using a defined protocol. Temperature, day of the week, and hour of the day were controlled, and dummy variables for each subject were controlled for subject specific risk factors. RESULTS: PM2.5 was associated with r-MSSD (-10.1% change for an interquartile range (IQR) increase in exposure (95% CI -2.8 to -16.9)) and PNN50, but stronger associations were seen with black carbon, an indicator of traffic particles, which was also associated with SDNN (-4.6% per IQR (95% CI -2.0 to -7.2)) and LFHFR. Secondary particles were more weakly associated with r-MSSD, as was ozone. No associations were seen with SO2 or NO2. CO had similar patterns of association to black carbon, which disappeared after controlling for black carbon. Black carbon had a substantially higher effect on SDNN in subjects who had had a previous myocardial infarction (-12.7%, 95% CI -5.7 to -19.25). CONCLUSIONS: Particles, especially from traffic, are associated with disturbances of autonomic control of the heart.

Acute exposure to environmental tobacco smoke and heart rate variability.

Environmental tobacco smoke (ETS) has been associated with cardiovascular mortality. Pathophysiologic pathways leading from ETS exposure to cardiopulmonary disease are still being explored. Reduced cardiac autonomic function, as measured by heart rate variability (HRV), has been associated with cardiac vulnerability and may represent an important pathophysiologic mechanism linking ETS and risk of cardiac mortality. In this study we evaluated acute ETS exposure in a commercial airport with changes in HRV in 16 adult nonsmokers. We conducted ambulatory electrocardiographic (ECG) monitoring for 8-hr periods while participants alternated 2 hr in nonsmoking and smoking areas. Nicotine and respirable suspended particle concentrations and participants' blood oxygen saturation were also monitored. We calculated time and frequency domain measures of HRV for periods in and out of the smoking area, and we evaluated associations with ETS using comparative statistics and regression modeling. ETS exposure was negatively associated with all measures of HRV. During exposure periods, we observed an average decrement of approximately 12% in the standard deviation of all normal-to-normal heart beat intervals (an estimate of overall HRV). ETS exposures were not associated with mean heart rate or blood oxygen saturation. Altered cardiac autonomic function, assessed by decrements in HRV, is associated with acute exposure to ETS and may be part of the pathophysiologic mechanisms linking ETS exposure and increased cardiac vulnerability.

Angerlike behavioral state potentiates myocardial ischemia-induced T-wave alternans in canines.

OBJECTIVES: The main goal of this study was to determine whether induction of an angerlike state can result in significant levels of T-wave alternans, a marker of electrical instability, in the normal and ischemic heart. BACKGROUND: Outbursts of anger have been implicated in the occurrence of myocardial infarction and sudden cardiac death, but the pathophysiologic mechanisms remain unknown. METHODS: A standardized behavioral challenge of eliciting an angerlike state was conducted before and during a 3-min period of coronary artery occlusion in six canines. RESULTS: Precordial T-wave alternans increased from 0.04 +/- 0.02 at baseline to 1.40 +/- 0.32 mV X ms (p < 0.05) during the angerlike response. When the angerlike state and myocardial ischemia were superimposed, the augmentation in T-wave alternans magnitude (to 3.27 +/- 0.61 mV X ms, p < 0.05) exceeded their additive effects, increasing by 130% over the angerlike state alone (p < 0.05) and by 390% over occlusion alone (p < 0.05). Adrenergic influences were reduced by the beta1-adrenergic receptor blocking agent metoprolol (1.5 mg/kg, intravenous), which diminished T-wave alternans magnitude (p < 0.0004 for all) during the angerlike response (from 1.40 +/- 0.32 to 0.80 +/- 0.17 mV x ms) and during the combined intervention (from 3.27 +/- 0.61 to 1.23 +/- 0.13 mV X ms). In five additional normal anesthetized canines, atrial pacing at 180 beats/min did not increase T-wave alternans magnitude monitored from lead II electrocardiogram. CONCLUSIONS: Provocation of an angerlike state results in T-wave alternans in the normal heart and potentiates the magnitude of ischemia-induced T-wave alternans. Elevation in heart rate during arousal does not appear to be the main factor in the development of alternans in the normal heart but may be an important component during myocardial ischemia. Enhanced adrenergic activity appears to mediate the effects in both the normal and ischemic hearts. T-wave alternans may constitute a useful electrophysiologic measure for clinical use in conjunction with behavioral stress testing or ambulatory monitoring.

Transatrial access to the normal pericardial space for local cardiac therapy: preclinical safety testing with aspirin and pulmonary artery hypertension.

The reliability, rapidity, and safety of nonsurgical, transatrial pericardial access for local cardiac therapy have been demonstrated in healthy animals. Since many patients take aspirin or have increased right-sided pressures, we evaluated the procedure's safety under these conditions. Transatrial pericardial access was performed in anesthetized pigs following aspirin administration (162 mg p.o., n = 6) or during experimental pulmonary artery hypertension (n = 4 different animals) and required only 3 minutes following guide catheter positioning. Platelet aggregability testing with arachidonic acid confirmed aspirin effectiveness. Mean pericardial fluid hematocrit was 0.1 +/- 0.1% after 2 days of aspirin therapy and 1.9 +/- 1.1% at sacrifice 24 hours later (NS). Mean pericardial fluid hematocrit was 1.0 +/- 0.5% after 45 minutes of pulmonary artery hypertension and 4.3 +/- 0.8% at sacrifice 30 minutes later (NS). Histologic analysis in both groups revealed a small thrombus and localized inflammation at the site of puncture. Neither aspirin use nor pulmonary artery hypertension causes significant bleeding into the pericardial space following transatrial access and thus does not preclude this route for local cardiac drug delivery.

Intrapericardial beta-adrenergic blockade with esmolol exerts a potent antitachycardic effect without depressing contractility.

Hyperadrenergic states of various etiologies can contribute to tachycardias. Systemic beta-adrenergic blockade suppresses sinus tachycardia but may adversely affect arterial blood pressure and contractility, because the drug gains access to myocardial cells as well as to the sinoatrial node. We examined whether intrapericardial beta-adrenergic blockade with esmolol could suppress tachycardia without reducing contractility as a result of limited drug diffusion, which would be sufficient to penetrate the superficial sinoatrial node but not the deeper myocardial layers. In five anesthetized pigs, we provoked a reflex heart rate increase of 50 beats/min with hemorrhage. The rapidly acting beta-adrenergic blocking agent esmolol (1 mg/kg) was administered intrapericardially using a new percutaneous transatrial access method and a catheter system that can be rapidly and safely introduced. Esmolol equivalently suppressed hemorrhage-induced sinus tachycardia when administered intrapericardially (from 192 to 158 beats/min at 5 min, p < 0.05) or intravenously (from 177 to 151 beats/min at 1 min, p < 0.05). The antitachycardic effect of intrapericardial esmolol was prolonged compared with intravenous esmolol (10 min vs. 3 min, p < 0.05). Intrapericardial esmolol did not affect blood pressure or left ventricular dP/dt max, an index of contractility, whereas intravenous esmolol decreased blood pressure at 1 min for 2 min (p < 0.05) and simultaneously decreased left ventricular dP/dt max at 1 min for < 2 min (p < 0.05). Intrapericardial esmolol suppresses adrenergically induced sinus tachycardia without decreasing contractility or blood pressure. The transatrial approach for intrapericardial delivery of certain 1-adrenergic blocking agents could be employed to control tachycardias in emergency care and surgical settings in patients with impaired cardiac contractility and propensity to hypotension.

Transient cardiorespiratory events during NREM sleep: a feline model for human microarousals.

Microarousals (MAs) are brief transient events that occur during normal sleep in humans and with increased frequency in disordered sleep, especially in association with sleep apnoea. In a feline model, we discovered transient cardiorespiratory events during nonrapid eye movement (NREM) sleep that exhibited consistent features with similarities to human MAs. It was observed that MAs have two distinct phases. Phase I (MAI) is characterized by an abrupt increase in electromyogram (EMG) amplitude (> 50%), increased electrooculogram (EOG) activity and accelerated frequency of hippocampal electroencephalographic (EEG) activity. MAI lasts 4.1 +/- 0.3 s. Phase II (MAII), lasting 9.8 +/- 0.8 s, is characterized by high frequency EEG activity, but EMG, EOG and hippocampal activity remain at baseline levels. Mean inspiratory rate begins to increase 15 s before the onset of the MA, followed 10 s later by the increase in mean heart rate. Mean respiratory rate decreases sharply through MAII, and returns to baseline levels 15 s after the MA. During MAII mean heart rate decreases quickly; there is increased respiratory irregularity, followed by a prolonged ventilatory overshoot. The abrupt shift in heart rate is coincident with the change in breath timing seen during MAII. Heart rate returns to baseline levels 10 s following the MA. Integrating our findings with those described previously in humans, we propose that MAs may serve as a homeostatic mechanism which is designed to restore cardiorespiratory function allowing the continuity of sleep.

Mechanisms of morbidity and mortality from exposure to ambient air particles.

The studies reported here assessed pathophysiologic mechanisms that result from exposure to concentrated ambient particles (CAPs) in animals with and without cardiopulmonary compromise. These studies were carried out to determine the biologic plausibility of epidemiologic observations of increases in particulate air pollution associated with increases in human morbidity and mortality. Dogs were exposed two at a time to CAPs or filtered air via tracheostomy for six hours per day on three consecutive days. The electrocardiogram (ECG) and breathing pattern were recorded continuously, and indicators of inflammation were also assessed. In one experimental design, normal dogs were exposed in pairs to CAPs and subsequently to filtered air or to filtered air and subsequently CAPs (the double CAPs/double sham design). Comparisons were made between the CAPs measurements and each dog's own sham responses. In another design, one dog was exposed to CAPs while the chambermate received a sham exposure; these experiments were followed by crossover of the protocol the subsequent week (the crossover design). Comparisons were made between the CAPs exposure and both the chambermate's sham and each dog's own sham responses. The crossover experiments were conducted in normal animals and in animals who had undergone balloon occlusion of the left anterior descending (LAD) coronary artery to induce myocardial compromise. The effects of CAPs in animals with induced chronic bronchitis were part of the original specific aims; because these studies were not fully pursued, the results are presented only in Appendix A. In normal dogs, analyses of all double CAPs and crossover studies revealed low frequency (LF) and high frequency (HF) powers for heart rate variability (HRV) that were significantly higher for CAPs exposure compared to sham exposure. Variation in day-to-day exposure concentrations, aerosol composition, and pathophysiologic responses were also found. The crossover design, continuous measures of aerosol mass, and biologic responses were incorporated in the development of a statistical model that allowed isolation of changes associated with CAPs from changes due to animal variations. Comparison of individual exposures with this model revealed a range from no response in any measured parameter to statistically significant changes in cardiac autonomic balance, pulmonary air flow, and breathing pattern. On days in which dogs showed statistically significant changes in responses, the findings were consistent in both cardiac and respiratory parameters. Days associated with significant increases in LF and HF HRV, LF/ HF HRV ratio, and heart rate standard deviation (HR SD) were also associated with decreases in average heart rate. These same days had decreases in respiratory frequency, tidal volume, minute volume, and peak flows with corresponding increases in respiratory cycle times and enhanced pause (Pauenh), a measure of bronchoconstriction. These cardiac and respiratory changes suggest an effect mediated via both the sympathetic nervous system and the vagus nerve. Alternatively, days associated with increased heart rate had decreases in the HR SD; decreases or no change in HF and LF HRV; increases in respiratory flows and volumes; and decreases in breathing cycle times, all suggesting only sympathetic nervous system mediation. When all data from the crossover design experiments were assessed with this model, the heart rate and respiratory rate were significantly decreased in relation to both cumulative and actual exposure and the LF HRV, LF/HF HRV ratio, HR SD, and all other respiratory parameters were significantly increased (p < 0.0001 for all). When cardiac data were grouped by days in which the air mass trajectory came from the north or northwest (versus west, south, east, or northeast), significant increases in HR SD and HF HRV and significant decreases in average heart rate were associated with the northwest trajectory. (ABSTRACT TRUNCATED)

Ambient pollution and heart rate variability.

BACKGROUND: We investigated associations between ambient pollution levels and cardiovascular function in a repeated measures study including 163 observations on twenty-one 53- to 87-year-old active Boston residents observed up to 12 times from June to September 1997. Particles with aerodynamic diameter

Air pollution and incidence of cardiac arrhythmia.

Air pollution episodes have been associated with increased cardiovascular hospital admissions and mortality in time-series studies. We tested the hypothesis that patients with implanted cardioverter defibrillators experience potentially life-threatening arrhythmias after such air pollution episodes. We compared defibrillator discharge interventions among 100 patients with such devices in eastern Massachusetts, according to variations in concentrations of particulate matter, black carbon, and gaseous air pollutants that were measured daily for the years 1995 through 1997. A 26-ppb increase in nitrogen dioxide was associated with increased defibrillator interventions 2 days later (odds ratio = 1.8; 95% confidence interval = 1.1-2.9). Patients with ten or more interventions experienced increased arrhythmias in association with nitrogen dioxide, carbon monoxide, black carbon, and fine particle mass. These results suggest that elevated levels air pollutants are associated with potentially life-threatening arrhythmia leading to therapeutic interventions by an implanted cardioverter defibrillator.

Inhaled concentrated ambient particles are associated with hematologic and bronchoalveolar lavage changes in canines.

Pulmonary inflammatory and hematologic responses of canines were studied after exposure to concentrated ambient particles (CAPs) using the Harvard ambient particle concentrator (HAPC). For pulmonary inflammatory studies, normal dogs were exposed in pairs to either CAPs or filtered air (paired studies) for 6 hr/day on 3 consecutive days. For hematologic studies, dogs were exposed for 6 hr/day for 3 consecutive days with one receiving CAPs while the other was simultaneously exposed to filtered air; crossover of exposure took place the following week (crossover studies). Physicochemical characterization of CAPs exposure samples included measurements of particle mass, size distribution, and composition. No statistical differences in biologic responses were found when all CAPs and all sham exposures were compared. However, the variability in biologic response was considerably higher with CAPs exposure. Subsequent exploratory graphical analyses and mixed linear regression analyses suggested associations between CAPs constituents and biologic responses. Factor analysis was applied to the compositional data from paired and crossover experiments to determine elements consistently associated with each other in CAPs samples. In paired experiments, four factors were identified; in crossover studies, a total of six factors were observed. Bronchoalveolar lavage (BAL) and hematologic data were regressed on the factor scores. Increased BAL neutrophil percentage, total peripheral white blood cell (WBC) counts, circulating neutrophils, and circulating lymphocytes were associated with increases in the aluminum/silicon factor. Increased circulating neutrophils and increased BAL macrophages were associated with the vanadium/nickel factor. Increased BAL neutrophils were associated with the bromine/lead factor when only the compositional data from the third day of CAPs exposure were used. Significant decreases in red blood cell counts and hemoglobin levels were correlated with the sulfur factor. BAL or hematologic parameters were not associated with increases in total CAPs mass concentration. These data suggest that CAPs inhalation is associated with subtle alterations in pulmonary and systemic cell profiles, and specific components of CAPs may be responsible for these biologic responses.

Preclinical safety testing of percutaneous transatrial access to the normal pericardial space for local cardiac drug delivery and diagnostic sampling.

The safety of a percutaneous method and streamlined catheter system to access the normal pericardial space via the right atrial appendage for drug delivery and diagnostic sampling was demonstrated in 20 anesthetized pigs. Access was successfully accomplished in all animals within 3 min of guide catheter positioning and was documented by fluoroscopic imaging and pericardial fluid sampling. The animals were sacrificed at 24 hr (n = 10) and 2 weeks (n = 10) for histopathologic analysis. Mean pericardial hematocrit was 1.1% +/- 0.3% at initial sampling, 4.3% +/- 1.4% at 24 hr (P = 0.005 vs. baseline), and 0.4% +/- 0.2% at 2 weeks (P = 0.13 vs. baseline). At 24 hr, there was local inflammatory reaction in the atrial wall and a small thrombus at the site of puncture. At 2 weeks, no significant inflammatory changes or pericarditis were evident. The technique is well tolerated with no apparent adverse complications. Advances in intrapericardial therapeutics and diagnostics will direct the clinical application of this novel approach in human subjects.

Heart rate variability associated with particulate air pollution.

BACKGROUND: Epidemiologic studies have linked fine particulate air pollution with cardiopulmonary mortality, yet underlying biologic mechanisms remain unknown. Changes in heart rate variability (HRV) may reflect changes in cardiac autonomic function and risk of sudden cardiac death. This study evaluated changes in mean heart rate and HRV in human beings associated with changes in exposure to particulate air pollution. METHODS: Repeated ambulatory electrocardiographic monitoring was conducted on 7 subjects for a total of 29 person-days before, during, and after episodes of elevated pollution. Mean HR, the standard deviation of normal-to-normal (NN) intervals (SDNN), the standard deviation of the averages of NN intervals in all 5-minute segments of the recording (SDANN), and the square root of the mean of squared differences between adjacent NN intervals (r-MSSD) were calculated for 24-hour and 6-hour time segments. Associations of HRV with particulate pollution levels were evaluated with fixed-effects regression models. RESULTS: After controlling for differences across patients, elevated particulate levels were associated with (1) increased mean HR, (2) decreased SDNN, a measure of overall HRV, (3) decreased SDANN, a measure that corresponds to ultralow frequency variability, and (4) increased r-MSSD, a measure that corresponds to high-frequency variability. The associations between HRV and particulates were small but persisted even after controlling for mean HR. CONCLUSIONS: This study suggests that changes in cardiac autonomic function reflected by changes in mean HR and HRV may be part of the pathophysiologic mechanisms or pathways linking cardiovascular mortality and particulate air pollution.

Heart rate surges during REM sleep are associated with theta rhythm and PGO activity in cats.

Rapid eye movement (REM) sleep is characterized by periods of profound cardiac autonomic activation evident in heart rate surges in humans and canines. Our goals were to determine whether or not the heart rate surge phenomenon occurs in cats and to characterize concurrent central nervous system activity. Cortical and hippocampal electroencephalogram, electromyogram, electrooculogram, pontogeniculooccipital (PGO) waves, subcutaneous electrocardiogram, and respiration were recorded. Bouts of sinus tachycardia lasting >/=3.5 s achieved a rate of 210 beats/min and were present predominantly during REM sleep. Heart rate during the surges rose an average of 26.4% from 132.5 +/- 2.0 beats/min before the surge to 167.5 +/- 2.6 beats/min (P < 0.001) and returned to 130.7 +/- 2.6 beats/min (P < 0.001). The heart rate surges were invariably accompanied by increased incidence and frequency of hippocampal theta waves and increased PGO wave frequency and incidence of PGO wave clusters and eye movement clusters. The occurrence of surges was dramatically reduced from 0.11 +/- 0.03 to 0.01 +/- 0.01/15 s of REM sleep (P = 0.02) by atenolol (0.6 mg/kg iv), indicating that the phenomenon is beta(1)-adrenergically mediated. These findings suggest a coupling between central activation of cardiac sympathetic nerves and the generation of hippocampal theta waves and PGO activity.

Persistent primary coronary dilation induced by transatrial delivery of nitroglycerin into the pericardial space: a novel approach for local cardiac drug delivery.

OBJECTIVES: We compared the effects of intrapericardial and intracoronary nitroglycerin on coronary cross-sectional area as assessed by intravascular ultrasound and demonstrated the feasibility of local cardiac drug delivery by a newly developed method to access the normal pericardial space through the right atrial appendage. BACKGROUND: Studies of nitric oxide (NO) donors have suggested that their antiarrhythmic and antiproliferative properties are more effective when administered by the intrapericardial rather than intravascular route. We postulated that NO donors delivered intrapericardially would also cause sustained coronary vasodilation without significant systemic hypotension. METHODS: Intrapericardial nitroglycerin (200 microg) was administered in five Yorkshire pigs. Coronary cross-sectional luminal area was measured with intravascular ultrasound at various time intervals. The effects of intracoronary nitroglycerin on coronary luminal area were used for comparison. RESULTS: Transatrial pericardial access required 1 to 3 min in all animals. Intrapericardial nitroglycerin was associated with a mean 31.7% increase in luminal area at 5 min (p < 0.001). Vasodilation peaked between 5 and 10 min and persisted for 15 min. In contrast, intracoronary nitroglycerin was associated with a smaller mean increase in luminal area (20.3% at 5 min, p < 0.01) that disappeared by 10 min. Significant systemic hypotension was observed at 3 min with intracoronary but not with intrapericardial nitroglycerin. CONCLUSIONS: Sustained coronary vasodilation can be achieved with intrapericardial delivery of nitroglycerin without systemic hypotension. Nitric oxide donors with longer half-lives could prove beneficial in the treatment of myocardial ischemic syndromes when administered through this route. Transatrial pericardial access offers a novel route for local cardiac drug delivery.

The surgical intensive care unit as a cost-efficient substitute for an operating room at a Level I trauma center.

Critically ill patients in the surgical intensive care unit (SICU) continue to require operative procedures. Traditionally, this has meant the transport of these critically ill patients out of the safe, monitored confines of the SICU to the operating room (OR). This can be hazardous to the patient, as well as expensive. Performing the procedures in the OR can avoid both the dangers of transport and the expense of the OR. Herein is a descriptive study of 80 procedures performed on 36 patients in the SICU. We believe that these data show that the SICU can be a cost-effective alternative to the OR in a trauma center in critically ill patients. Significant cost savings may be realized without increasing the iatrogenic or infectious complications.

Transatrial access to the normal pericardial space: a novel approach for diagnostic sampling, pericardiocentesis, and therapeutic interventions.

BACKGROUND: A nonsurgical means to access the normal pericardial space could provide opportunities for diagnostic sampling and therapeutic interventions. Because there are currently no approved nonsurgical methods to accomplish this, we tested a new approach in large animals. METHODS AND RESULTS: A catheter system was employed in a percutaneous approach from a femoral vein to pierce the right atrial appendage. Pericardial access was confirmed by placement of a radiopaque guidewire visible under fluoroscopy (6 dogs, 13 pigs). In 7 of the pigs, pericardial tamponade, produced by injection of saline or heparinized blood into the pericardial space through this route, was confirmed by fluoroscopy and hemodynamic evidence. The feasibility and safety of this access route were tested with multiple repetitions in all 19 animals. At the end of each of the 17 acute experiments, direct inspection after thoracotomy revealed no hemopericardium, laceration, or bleeding on catheter withdrawal. In 24-hour survival studies performed in 2 of the 6 dogs, the animals exhibited no behavioral signs of discomfort or untoward consequences on recovery from anesthesia. Histology revealed only a small (approximately 1-mm) fibrinous plug at the site of puncture. CONCLUSIONS: The percutaneous approach via the right atrial appendage provides a rapid, safe route to access the normal pericardial space for diagnostic sampling and to alleviate high-volume and low-volume (<200 mL) pericardial effusions. The access route is potentially useful for selective administration of therapeutic agents, growth factors, gene vectors, and cardioactive and vasoactive agents to the heart.

Primary vagally mediated decelerations in heart rate during tonic rapid eye movement sleep in cats.

Rapid eye movement (REM) sleep results in profound state-dependent alterations in heart rate. The present study describes a novel phenomenon of a primary deceleration in heart rate that is not preceded or followed by increases in heart rate or arterial blood pressure and occurs primarily during tonic REM sleep. The goals were to characterize the primary decelerations and to provide insights on the underlying central and peripheral autonomic mechanisms. Cats were chronically implanted with electrodes to record electroencephalogram, pontogeniculooccipital wave activity in lateral geniculate nucleus, hippocampal theta rhythm, electromyogram, electrooculogram, respiration (diaphragm), and electrocardiogram. Arterial blood pressure was monitored from a carotid artery catheter. R-R interval fluctuations were continuously tracked using customized software. The muscarinic blocking agent glycopyrrolate (0.1 mg/kg i.v.) and the beta-adrenergic blocking agent atenolol (0.3 mg/kg i.v.) were administered in alternating sequence with a 90- to 120-min interval. Glycopyrrolate immediately eliminated the decelerations during REM sleep. Atenolol alone had no effect on their frequency. These findings suggest that a change in the centrally induced pattern of autonomic activity to the heart is responsible for the primary decelerations, namely, a bursting of cardiac vagal efferent fiber activity.