Mitochondrial extracellular vesicles, autoimmunity and myocarditis

For many decades viral infections have been suspected as 'triggers' of autoimmune disease, but mechanisms for how this could occur have been difficult to establish. Recent studies have shown that viral infections that are commonly associated with viral myocarditis and other autoimmune diseases such as coxsackievirus B3 (CVB3) and SARS-CoV-2 target mitochondria and are released from cells in mitochondrial vesicles that are able to activate the innate immune response. Studies have shown that Toll-like receptor (TLR)4 and the inflammasome pathway are activated by mitochondrial components. Autoreactivity against cardiac myosin and heart-specific immune responses that occur after infection with viruses where the heart is not the primary site of infection (e.g., CVB3, SARS-CoV-2) may occur because the heart has the highest density of mitochondria in the body. Evidence exists for autoantibodies against mitochondrial antigens in patients with myocarditis and dilated cardiomyopathy. Defects in tolerance mechanisms like autoimmune regulator gene (AIRE) may further increase the likelihood of autoreactivity against mitochondrial antigens leading to autoimmune disease. The focus of this review is to summarize current literature regarding the role of viral infection in the production of extracellular vesicles containing mitochondria and virus and the development of myocarditis.

Use of a telephone nursing line in a pediatric neurology clinic: one approach to the shortage of subspecialists

OBJECTIVE

There are not enough pediatric neurologists to meet the many needs of pediatric neurology patients. The Hospital for Sick Children has responded by expanding the nursing role in the pediatric neurology outpatient clinic. The objective of this study was to examine the use of a telephone nursing line in this hospital-based pediatric neurology clinic.

METHODS

A cross-sectional study was performed on all telephone call records collected during a 2-week study period. Each initial incoming call concerning a patient was counted as an index call. Associations between clinic type or diagnosis and length of telephone calls were assessed using the chi(2) test.

RESULTS

A total of 208 index calls were received, generating a total of 597 incoming and outgoing calls. The most common clinic types were Epilepsy clinic (35.6%) and General Neurology clinic (32.7%), and the most common patient diagnoses were epilepsy (63.5%) and developmental delay (45.2%). Most patients were between the ages of 1 and <7 years (33.9%) and 12 and <18 years (32.8%) and male (55.2%). Most calls were made by mothers (57.2%) to ask about medical administrative issues (28.4%) and/or symptoms (27.9%). Physicians were notified for 47.1% of calls; nurses were twice as likely to notify physicians for calls concerning new symptoms (relative risk: 2.1; 95% confidence interval: 1.6-2.7). Most calls required between 1 and 5 minutes (49.0%). Long telephone calls (>10 minutes) were strongly associated with a diagnosis of epilepsy.

CONCLUSIONS

There is a high demand for the neurology nursing line in our clinic. Most telephone calls and most long telephone calls concerned patients with epilepsy. Nurses managed more than half of all telephone calls without physician assistance. Use of a nursing line can aid in the provision of care to complicated subspecialty patients. Additional strategies are needed to optimize delivery of care to high-need medical populations.

The relationship of electronically monitored physical activity to blood pressure, heart rate, and the circadian blood pressure profile

We studied how closely changes in electronically monitored physical activity are reflected in changes in blood pressure and heart rate in a group of untreated hypertensive subjects. Thirty-nine hypertensive patients (office blood pressure > 140/ 90 mm Hg) of mean age 57 +/- 10 years (mean +/-SD) wore an ambulatory blood pressure monitor and a wrist actigraph simultaneously. Both average and peak activity for 5 min before each valid blood pressure reading were determined, as was average activity for awake and sleep periods, determined by patient kept diaries. For the overall group, awake and 24-h activities were inversely correlated to age (n = 39, r = -0.42; P = 0.01 and n = 39, r = -0.38; P = 0.01, respectively). No correlation was found between group awake activity and group-average blood pressure or heart rate. For individual patients, there was marked variation in the degree of correlation between awake activity measures (both peak and average) and blood pressure and heart rate. The strongest positive correlation was between activity levels and the heart rate-pressure product. Nondipper profile hypertensives had higher sleep activity than dipper hypertensives (44 +/- 28 units/min v 25 +/- 20 units/min, df = 37, t = 2.12; P = 0.04), but awake activity levels were similar. The higher sleep activity remained after adjustment for age. These findings indicate that the relationship between actigraphic activity and hemodynamic parameters is highly variable and that the rate-pressure product is the strongest correlate of short-term activity. Furthermore, hypertensives with the nondipper profile have higher sleep activity than dipper hypertensives. These findings stress the need for further study into the role of day-to-day activity in determining ambulatory blood pressure and heart rate variability.

Two-domain motif for IgG-binding activity by group A streptococcal emm gene products

A biological role for the non-immune binding of human IgG by group A streptococci is evidenced by its strong association with a subpopulation of strains giving rise to tissue-specific infection. IgG-binding activity lies within many of the M and M-like surface proteins (encoded by emm genes), and several structurally distinct IgG-binding sites are known to exist. In this report, two adjacent IgG-binding domains, differing in their specificity for human IgG subclasses, are localized within the M-like protein, protein H. The putative coding regions for the two IgG-binding domains were mapped for 82 epidemiologically unrelated strains. Both coding regions are associated with phylogenetically distant emm genes, supporting a role for horizontal transfer and intergenomic recombination in the evolution of emm genes. In most instances, the two coding regions are tightly linked, suggesting that there exist strong selective pressures to maintain a two-domain binding motif. Both coding regions are found among all strains bearing emm gene markers associated with impetigo lesions as the principal tissue reservoir, but are absent from most strains that exhibit markers for a predominant nasopharyngeal reservoir. The data support the hypothesis that the pathogenic potential of an isolate is dictated, at least in part, by its unique array of multifunctional emm gene products.

Determinants of the white-coat effect in hypertensive subjects

To determine the magnitude and the relationships of the difference between office and awake ambulatory blood pressures (BP) (white-coat effect) in ambulatory hypertensive patients, 64 consecutive patients referred to the ambulatory BP monitoring laboratory were studied. All subjects were evaluated prospectively by study nurse, study doctor, and ambulatory BP measurements. Order of measurements was randomized and observers were blinded to each others readings. No differences were found in the white-coat effects among study nurse (22/14 +/- 20/9 mm Hg), study doctor (27/12 +/- 20/10 mm Hg) and referring doctor (19/11 +/- 18/10 mm Hg). Similarly, female and male patients exhibited similar white-coat effects on the day of ambulatory monitoring. Older patients (> or = 65 years) displayed higher mean systolic white-coat effects than younger patients (29 +/- 18 mm Hg vs 19 +/- 19 mm Hg, P = 0.04). Multivariate analysis using the mean average systolic white-coat effect as the dependent variable and age, gender, treatment status, body mass index (BMI) and duration of hypertension as independent variables showed a significant independent role for age. In contrast, no clinical correlates of the diastolic white-coat effect were found. Older patients are more likely to display a systolic white-coat effect in the medical care environment.

Multicenter assessment of the QuietTrak ambulatory blood pressure recorder according to the 1992 AAMI guidelines

To clinically evaluate the QuietTrak ambulatory blood pressure (BP) recorder (Tycos-Welch-Allyn, Arden, NC), we assessed the device according to the performance criteria set out by the 1992 Association for the Advancement of Medical Instrumentation (AAMI) guidelines. The QuietTrak is a portable, noninvasive recorder that uses an auscultatory measuring system. As recommended in the 1992 AAMI guidelines, a large, heterogeneous population was recruited for the study using three clinic sites to assess accuracy and clinical performance. In addition, observer agreement and the effects of age, arm circumference, heart rate, posture, and blood pressure level on the observer-device differences were analyzed. There were 1098 simultaneous, same arm BP measurements performed in 122 subjects by the QuietTrak recorder versus two skilled clinicians per site using a teaching stethoscope and 24-h blood pressure recordings performed in 46 subjects to assess reliability of the monitor. The differences in observers for all sites were 0.7/-0.5 +/- 3.8/3.5 mm Hg with 89% of the BPs within 5 mm Hg. The mean difference between observer average and the device (all positions) was 0.3/-1.5 +/- 5.0/7.5 mm Hg. The agreement between the QuietTrak and mercury column determinations was within 10 mm Hg for 92 to 94% of systolic readings and 91 to 93% of diastolic readings, depending on the posture. The limits of agreement (2 standard deviations about the mean difference) between observers and the device for systolic BP tended to be lower for the sitting position (-11 to 10 mm Hg) compared to supine (-14 to 13 mm Hg) and standing (-14 to 14 mm Hg) positions.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term reproducibility of ambulatory blood pressure

OBJECTIVE

To compare the reproducibility of ambulatory and office blood pressure readings in established hypertensive subjects when studies are repeated at extended time intervals.

SUBJECTS

Twenty-five hypertensive patients (office diastolic blood pressure > or = 90 mmHg) who were off antihypertensive therapy for at least 4 weeks and had repeat office and ambulatory blood pressures at least 3 months apart under similar study conditions.

METHODS

On the same day, patients underwent office blood pressure readings measured by mercury column sphygmomanometry and then by ambulatory blood pressure monitoring. Ambulatory blood pressure monitoring was done for 24 h, and awake and sleep periods were divided according to a diary kept by each patient. A second study was performed in an identical manner at a mean +/- SD interval of 23 +/- 24 months (range 3-80, median 15). The agreement between studies was assessed by correlation coefficients, coefficients of variation and standard deviation of the differences (SDD).

RESULTS

There were no significant differences in office, 24-h, awake and sleep mean blood pressures between the two studies. Mean 24-h systolic and diastolic blood pressures were 16 and 14 mmHg lower, respectively, than office blood pressure values. Correlation coefficients were significantly higher for 24-h ambulatory blood pressure than office blood pressure, whereas the SDD between visits was significantly lower for 24-h ambulatory blood pressure than office blood pressure.

CONCLUSIONS

These data demonstrate that long-term reproducibility of ambulatory blood pressure is superior to that for office measurement. One implication of this finding is that, in long-term clinical pharmacology trials utilizing ambulatory blood pressure, fewer subjects would be required than for studies that used office blood pressure end-points.

Management of hypertension after ambulatory blood pressure monitoring

OBJECTIVE

To study the test-ordering behavior of practicing physicians regarding ambulatory monitoring of blood pressure and to assess changes in patient management after this study.

DESIGN

Cross-sectional assessment of physicians' practice habits regarding the ordering of ambulatory blood pressure monitoring and a longitudinal study of patient management after monitoring.

SETTING

Physicians' offices in central Connecticut.

PARTICIPANTS

Two hundred thirty-seven consecutive patients referred by 65 community- and hospital-based physicians.

MEASUREMENTS

Indications for ambulatory blood pressure monitoring, changes in diagnosis and therapy, and office blood pressures before and after the ambulatory blood pressure study.

RESULTS

The main indications for ordering the test included borderline hypertension (27% of studies ordered), assessment of blood pressure control during drug therapy (25%), evaluation for "white coat" or "office" hypertension (22%), and drug-resistant hypertension (16%). After the ambulatory blood pressure study, only 13% of the patients had further testing (for example, echocardiography); the diagnosis was changed in 41% of the patients, and antihypertensive therapy was changed in 46%. In 122 patients for whom data were complete, office blood pressure measured by the referring physician decreased from 161/96 +/- 22/12 mm Hg before the ambulatory blood pressure study to 151/86 +/- 27/12 mm Hg 3 months after the study (P = 0.004 for systolic blood pressure and P < 0.001 for diastolic blood pressure). One to 2 years after the study, office blood pressure was 149/86 +/- 24/12 mm Hg (P > 0.2 compared with 3 months after the study). Seventy-two percent of the patients had a lower office blood pressure within 3 months of the ambulatory blood pressure study.

CONCLUSIONS

Practicing physicians use ambulatory blood pressure recordings for appropriate indications, and data from the monitoring studies affected the management of patients with hypertension.

Clinical usefulness of ambulatory blood pressure monitoring

During the last decade, ambulatory blood pressure monitoring (ABPM) made a transition from a method reserved for clinical investigators to a technique considered useful by practicing physicians in assessing certain problems in hypertension. Recent recommendations of the National High Blood Pressure Education Program (NHBPEP) Working Group on Ambulatory Blood Pressure Monitoring suggested using ABPM for a number of clinical problems, including borderline hypertension without target organ damage, evaluation of drug resistance, and white-coat hypertension. We evaluated the clinical indications for ordering ABPM by Connecticut physicians both in hospital and community-based practices. Through specific questionnaires, the clinical indications used by referring physicians to order ABPM and their inclinations for future use of the methodology were assessed. Forty-seven of 70 physicians (65%) responded to the questionnaire, basing their answers on 237 patients. The majority of physicians were internists (57%) or cardiologists (25%). Leading indications for patient referral for ABPM included borderline hypertension (27%), assessment of drug therapy/BP control (25%), and possible white-coat hypertension (22%). Far fewer referrals were observed for severe hypertension or as a routine test for the diagnosis of hypertension. These data suggest that practicing physicians have become aware of the usefulness of ambulatory blood pressure recordings and are following the NHBPEP guidelines on referral for the study.

A multicenter evaluation of the A&D TM-2420 ambulatory blood pressure recorder

The A&D TM-2420 (A&D Engineering, Milpitas, CA) is an automatic, portable, noninvasive blood pressure (BP) recorder which uses a dual microphone system for the detection of Korotkoff sounds. Its accuracy and clinical performance were assessed in a multicenter study that also addressed issues such as observer agreement and the effects of age, arm circumference, heart rate, posture, and blood pressure level on the observer-device differences. We compared 906 simultaneous, same-arm BP measurements in 151 subjects using the TM-2420 versus two skilled clinicians per site using a teaching stethoscope. The agreement between the TM-2420 and mercury column determinations were within 10 mm Hg for 86 to 91% of systolic readings and 91 to 94% of diastolic readings, depending on the posture; a level of agreement which would receive a 'B+' grade from the recent British Hypertension Society guidelines. The limits of agreement (2 standard deviations about the mean difference) for systolic BP between observers and the TM-2420 tended to be greater for the standing position (-20 to 15 mm Hg) compared to supine (-14 to 12 mm Hg) and seated (-13 to 8 mm Hg) positions. Limits of agreement between the observers and device were not dependent upon age, heart rate, arm size, or blood pressure level. Twenty-four-hour blood pressure monitoring in two of the four centers demonstrated an error code rate of 3.4%, excluding 'retries' that are one of the device's features. These data demonstrate an acceptable level of accuracy and performance of the sixth generation of the TM-2420 for use in clinical practice and research.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical evaluation of the Accutracker II ambulatory blood pressure monitor: assessment of performance in two countries and comparison with sphygmomanometry and intra-arterial blood pressure at rest and during exercise

In order to assess the Accutracker II (Suntech Medical Instruments, Raleigh, North Carolina, USA), a relatively new ambulatory blood pressure (BP) monitor, versus standard forms of BP measurement, we compared same- and contralateral-arm measurements made, via a t-tube connected to a mercury column sphygmomanometer, by two clinicians using a teaching stethoscope and by intra-arterial recordings. Average systolic BP values obtained using the Accutracker II were similar to both the mercury column and intra-arterial determinations, but average diastolic BP values were lower than both the average mercury column (2.8 +/- 4.2 mmHg, P less than 0.001) and intra-arterial measurements (2.0 +/- 4.7 mmHg, P less than 0.02). During isometric exercise and 100-watt bicycle exercise, there were greater limits of agreement for the differences in BP between the Accutracker II and the intra-arterial transducer than were observed for the resting measurements, but these differences were no greater than those observed between intra-arterial and clinician-determined BP measurements. The clinical performance of the Accutracker II was assessed using 119 hypertensive subjects (84 in Norway and 35 in the USA) who wore the monitor for 24 h. While there was good-to-excellent data return in both countries, there were significantly less error codes secondary to excessive arm motion observed in Norway. Our data demonstrate that the Accutracker II is quite accurate compared with both the mercury column and intra-arterial methods of measuring BP, and performs well during 24 h outpatient activities. Our findings also indicate certain geographical differences which may be important in the performance of ambulatory BP-monitoring studies.

Clinical evaluation of the Colin ABPM 630 at rest and during exercise: an ambulatory blood pressure monitor with gas-powered cuff inflation

The Colin ABPM 630 is a silent, gas-powered (CO2) ambulatory blood pressure monitor which uses both ausculatory and/or oscillometric methods to measure blood pressure. We compared simultaneous, same-arm blood pressures obtained with the monitor with those made by two blinded, skilled clinicians using a mercury column and teaching stethoscope. In a second study, the monitor readings were also compared with opposite-arm intra-arterial recordings of blood pressure. The group mean systolic blood pressures obtained by the Colin monitor via the Korotkoff mode were almost identical to the mercury column readings (127.8 +/- 19.4 versus 128.1 +/- 19.3 mmHg, P = NS) and the limit of agreement (2 standard deviations) for the differences in the two methods was +/- 9 mmHg. The diastolic blood pressure obtained by the Colin monitor was significantly lower than the clinician's readings (-6.0 +/- 5.9 mmHg, P less than 0.0001). Similar findings were obtained with the oscillometric mode, however, the mean systolic blood pressure given by the monitor was slightly higher than that given by the mercury column (1.9 +/- 4.5 mmHg, P less than 0.001). In contrast to the mercury column comparisons, the mean diastolic blood pressure obtained with the monitor was nearly the same as the mean intra-arterial diastolic blood pressure for both the Korotkoff (0.1 +/- 5.6 mmHg) and the oscillometric modes (1.2 +/- 6.3 mmHg). During 100-watt bicycle exercise, there was a considerably greater scatter in the individual comparisons of the monitor and intra-arterial blood pressure than that seen in the measurements at rest, but the group means were again similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Average daily blood pressure, not office blood pressure, determines cardiac function in patients with hypertension

To determine the presence of cardiac disease in hypertensive patients with disparities between physician and out-of-office blood pressures, we prospectively studied three groups of age-matched patients identified by both casual (office) and ambulatory blood pressures: (1) office blood pressure greater than 140/90 mm Hg and awake ambulatory blood pressure of 130/80 mm Hg or less ("office" hypertensives); (2) office blood pressure less than 135/85 mm Hg and awake ambulatory blood pressure of 130/80 mm Hg or less (normotensives); and (3) office blood pressure greater than 140/90 mm Hg and awake ambulatory blood pressure of 140/90 mm Hg or greater ("daytime" hypertensives). In the patients with office hypertension, both the left atrial index and left ventricular mass index were significantly less than in patients with daytime hypertension and not statistically different from those of the normotensive subjects. Left ventricular filling rate at rest and ejection fraction at peak exercise were significantly greater in the office hypertensive group than in the daytime hypertensive group but were no different from those of the normotensive subjects. These findings demonstrate that patients with blood pressure elevation only in the physician's office have cardiac size and function similar to those of normotensive individuals. Thus, the average daily blood pressure best predicts cardiac end-organ damage.

Selective dopamine-1 agonist therapy in severe hypertension: effects of intravenous fenoldopam

To determine the effects of dopamine-1 agonist therapy in severe hypertension, blood pressure, heart rate, catecholamines and left ventricular function were studied in 18 patients (10 with renal disease) with diastolic blood pressure greater than 120 mm Hg (range 124 to 160) after intravenous fenoldopam therapy. Constant infusions of fenoldopam were titrated upward every 10 to 20 min from an initial dose of 0.1 microgram/kg per min to a maximal dose of 0.9 microgram/kg per min. The therapeutic goal of a supine diastolic blood pressure of less than 110 mm Hg was achieved in every patient within 1 h at an average dose of 0.34 +/- 0.22 microgram/kg per min. Blood pressure decreased from 214/134 +/- 33/10 mm Hg at baseline to 170/96 +/- 29/7 mm Hg (p less than 0.0001) at 3 h, whereas heart rate increased from 77 +/- 23 to 88 +/- 21 beats/min (p less than 0.01). Plasma norepinephrine increased during the fenoldopam infusion; epinephrine and dopamine levels did not change. Two indexes of left ventricular function (end-systolic dimension and isovolumic relaxation time) improved during the fenoldopam infusion, but mitral flow velocities during ventricular filling were unchanged. Side effects of intravenous fenoldopam were mild, transient and associated with the marked vasodilatory properties of the drug. Thus, fenoldopam is safe and effective as a parenteral monotherapy in patients with severe essential and renovascular hypertension. Preliminary data suggest that blood pressure reduction with selective dopamine-1 agonist therapy is accompanied by improved left ventricular function.

Clinical validation of the accutracker, a novel ambulatory blood pressure monitor using R-wave gating for Korotkoff sounds

We compared simultaneous, same-arm blood pressure (BPs) obtained with the Accutracker, an ambulatory blood pressure (BP) monitor, which uses R-wave gating for Korotkoff sounds to those of both a blinded, skilled clinician using a mercury column and a three-channel graphic display of cuff pressure tracings, Korotkoff sounds, and ECG tracing. Eighteen subjects, with a wide variety of BPs, heart rates, and ages, participated in the study. The systolic BP obtained by the ambulatory recorder, clinician, and the three-channel strip chart recorder were 132 +/- 23 mmHg, 132 +/- 24 mmHg, and 133 +/- 25 mmHg, (all NS), respectively. Accutracker recorder-determined systolic BP correlated highly both with the clinician and strip chart readings (r = 0.98 and 0.97, respectively; p less than 0.0001 for both). The diastolic BP obtained by the Accutracker recorder was slightly, but significantly, lower than the clinician's readings (76 +/- 12 mmHg vs. 81 +/- 13 mmHg; p less than 0.005) and similar to the strip chart recorder readings (76 +/- 12 mmHg vs. 77 +/- 12 mmHg; NS). In 32 young, healthy subjects with no activity restrictions, 91% of the raw BP data from 24-hour ambulatory recordings was acceptable using strict deletion criteria. These data demonstrate that the Accutracker is highly accurate compared with clinician-determined blood pressures. The lower diastolic BP readings may stem from the ability of this device to detect softer Korotkoff sounds than can be detected by the clinician. These findings should be taken into consideration when using ambulatory BP monitoring in clinical trials of antihypertensive drugs.

Effects of chronic cetamolol therapy on resting, ambulatory, and exercise blood pressure and heart rate

We studied blood pressure (BP) and heart rate (HR) responses in 12 patients with hypertension who were receiving cetamolol, a cardioselective beta-blocker with intrinsic sympathomimetic activity. The BP and HR parameters were evaluated at rest (casual, office readings), with ambulatory BP monitoring, and after treadmill exercise testing. At a mean (+/- SD) dose of 46 +/- 21 mg/day, casual supine BP decreased by 10/12 mm Hg (P less than 0.05 for systolic; P less than 0.01 for diastolic) compared with placebo, while HR decreased 4 bpm. Cetamolol resulted in a significant reduction in the mean 24-hour systolic BP. The most striking reduction occurred in the BP at work (23 mm Hg), with almost no decrease in the BP during sleep. Ambulatory HR reductions occurred while the subjects were at work (9 bpm; P less than 0.05) but not while at home (awake) or during sleep. The mean duration of exercise was the same during cetamolol and placebo phases, but both HR and BP fell significantly at peak performance after cetamolol. These data suggest that cetamolol reduces BP without lowering HR at rest. During periods of increased adrenergic activity such as work and dynamic exercise, both HR and BP are reduced.

Effects of chronic nitrendipine on casual (office) and 24-hour ambulatory blood pressure

To assess the clinical efficacy of chronic nitrendipine therapy in mild to moderate essential hypertension, we studied blood pressure (BP) and heart rate responses in 22 subjects receiving maintenance nitrendipine therapy. Ten subjects (45%) whose hypertension was controlled with chronic monotherapy had an 11/12 mm Hg decrease in supine BP (P less than 0.05) with a mean (+/- SD) dose of 71 +/- 15 mg/day. The 12 (55%) subjects whose hypertension was not controlled with monotherapy had a comparatively higher baseline BP than the other 10 (156/105 +/- 10/6 compared with 150/98 +/- 15/4 mm Hg; P less than 0.05). Eight of the 10 subjects demonstrating office BP control with chronic nitrendipine monotherapy who also had full-time employment underwent continuous ambulatory BP monitoring before and after maintenance monotherapy. Nitrendipine induced a reduction in the mean 24-hour BP and mean BP at home, but did not reduce the BP during work or while asleep. These data suggest that nitrendipine lowers BP when assessed by casual office methods. The ambulatory BP monitor data demonstrate that the hypotensive response to chronic nitrendipine is modified during work periods, which are generally associated with increased adrenergic activity. Ambulatory BP monitoring may be superior to office (casual) monitoring in the assessment of the overall efficacy of antihypertensive drugs.