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PubMed2005

Left atrial systolic reserve in idiopathic vs. ischaemic-dilated cardiomyopathy.

PURPOSE: There are studies indicating more pronounced left atrial (LA) systolic dysfunction at rest in idiopathic (IDDC) than in ischaemic-dilated cardiomyopathy (ISDC). It was hypothesized that the findings would be similar with regards LA systolic reserve. METHODS: Twenty-six patients with IDDC, 28 with ISDC and 25 normal controls underwent low-dose dobutamine stress echocardiography (5-10 microg kg(-1) min(-1) IV). Left atrial volumes were echocardiographically determined at rest and during stress at the mitral valve opening (maximal, Vmax), electrocardiographic P wave (onset of atrial systole, Vp) and mitral valve closure (minimal, Vmin) from the apical 4- and 2-chamber views (biplane area-length method). Left atrial systolic function was assessed with the LA-active emptying volume (ACTEV) = Vp-Vmin and fraction (ACTEF) = ACTEV/Vp. RESULTS: Vmax at rest was similar in IDDC and ISDC and greater than in the controls (54.2 +/- 12 vs. 48.5 +/- 18 vs. 27.1 +/- 6.3 cm(3) m(-2), respectively, P < 0.001) and did not change with stress (53.9 +/- 13.8 vs. 46.9 +/- 16.2 vs. 25.8 +/- 5.9 cm(3) m(-2), P < 0.001). The ACTEV at rest was similar in IDDC and ISDC and greater than in the controls (8.6 +/- 3.5 vs. 9.7 +/- 2.9 vs. 6.1 +/- 2.2 cm(3) m(-2) P < 0.01), whereas during the dobutamine infusion it remained unaltered in IDDC (10.8 +/- 4.6 cm(3) m(-2), P = NS vs. rest) and increased in ISDC (11.8 +/- 3.3 cm(3) m(-2), P < 0.05) and the controls (13.1 +/- 3.2 cm(3) m(-2), P < 0.01). The ACTEF was lower in IDDC than ISDC and the controls at rest (20 +/- 10% vs. 33 +/- 8% vs. 36 +/- 10%, P < 0.01). Dobutamine infusion was associated with no significant increase in ACTEF in IDDC (25 +/- 12%, P = NS vs. rest), and with an increase in this variable in ISDC (39 +/- 10%, P < 0.05) and the controls (49 +/- 12%, P < 0.01). CONCLUSIONS: Dobutamine infusion is associated with an increase in LA ACTEV and fraction in ISDC and no significant change in these indices in IDDC. These findings indicate a reduced LA systolic reserve in IDDC.

Adult↗
PubMed2001

Low sodium inotropy is accompanied by diastolic Ca2+ gain and systolic loss in isolated guinea-pig ventricular myocytes.

We measured sarcolemmal Ca2+ fluxes responsible for the positive inotropic effects of solutions with reduced Na+ concentration in voltage-clamped guinea-pig ventricular myocytes; intracellular Ca2+ concentration ([Ca2+]i) was measured with Indo-1. Reduction of external Na+ concentration by 50 % (to 67 mM) produced an increase in systolic [Ca2+]i accompanied by a decrease in Ca2+ entry via the L-type Ca2+ current. With reduced Na+ concentration, there was an initial decrease in the Na+-Ca2+ exchange current on repolarization followed by an increase to greater than control. We attribute this initial decrease to a decrease in the Na+ gradient and the subsequent increase to a fall in intracellular Na+ concentration and increase in systolic [Ca2+]i. The decreased L-type Ca2+ current and increased Ca2+ efflux on Na+-Ca2+ exchange resulted in a calculated systolic loss of Ca2+. The calculated systolic loss of Ca2+ was accompanied by a measured increase in sarcoplasmic reticulum (SR) Ca2+ content. Reduction of the external Na+ concentration also produced an outward shift of holding current which was blocked by Ni2+. This is taken to represent Ca2+ influx via Na+-Ca2+ exchange. When diastolic influx is taken into account, the observed gain in SR Ca2+ content can be predicted. The measurements show that, in reduced Na+, much of the entry of Ca2+ into the cell occurs during diastole (via Na+-Ca2+ exchange) rather than in systole (via the L-type Ca2+ current).

Animals↗
PubMed1995

The velocity distribution in the aortic annulus at different times during systole is mainly determined by the pattern of flow convergence in the left ventricular outflow tract--an experimental study using Doppler colour flow mapping.

An experimental study in 10 open chest normal pigs (body weight: 24 +/- 1 kg) was carried out to explore the relationship between the velocity distribution in the aortic annulus and the pattern of flow convergence in the left ventricular outflow tract. The cross-sectional velocity profiles in the aortic annulus were constructed by using Doppler colour flow mapping with a previously validated time-interpolation method. The pattern of flow convergence in the left ventricular outflow tract was quantified by measuring the colour flow areas on the anterior and posterior sides of the central axis of the aortic annulus, and calculating their difference. The dynamic changes of the velocity distribution, the pattern of flow convergence and the septal angle throughout systole were observed. The velocity distribution in the aortic annulus changed according to the pattern of flow convergence in the left ventricular outflow tract. During early systole, the pattern of flow convergence was most asymmetrical. With the central longitudinal axis of the aortic annulus as a reference, the main part of the converging flow was along the anterior wall of the left ventricular outflow tract. Consequently, the velocity profile in the aortic annulus was most skewed during the early systole, with the highest velocity along the anterior wall. Towards late systole, the pattern of flow convergence became more and more symmetrical, and the velocity distribution in the aortic annulus gradually became flat. A significant correlation was found between the extent of asymmetry of the pattern of flow convergence in the left ventricular outflow tract and the extent of skewness of the velocity distribution in the aortic annulus (r = 0.69, P < 0.001). Throughout systole, septal angle increased very slightly (from 35 +/- 3 to 38 +/- 3 degrees, P < 0.01). The pattern of flow convergence in the left ventricular outflow tract is a major determinant of the velocity distribution in the aortic annulus in pigs.

Animals↗
PubMed2005

Time spent moving is related to systolic blood pressure among older women.

Isolated systolic hypertension is present in the majority of older women. Exercise is an attractive antihypertensive lifestyle therapy for older women with isolated systolic hypertension, but the amount of exercise needed to reduce blood pressure (BP) is not clear. Evidence is accumulating that lower levels of physical exertion are associated with decreased BP. The authors sought to determine if BP was related to daily time spent moving. Participants were 109 women (mean +/- SD, 75.2+/-7.2 yr). A majority (63.3%) had hypertension, and 48.6% had isolated systolic hypertension. Systolic BP was lower among women moving > or =5 h/d (142.2+/-18.7 mm Hg) than those moving <5 h/d (149.8+/-19.0 mm Hg) (p=0.038). Multiple regression analysis indicated that the potentially strong confounding effects of antihypertensive medication use, adiposity, and age did not eliminate these favorable associations between daily time spent moving and systolic BP. Older women should be encouraged to regularly engage in physical activities typical of everyday life such as walking because of its BP benefits.

Aged↗
PubMedDate not supplied

Hypertension in the elderly: a review of the importance of systolic blood pressure elevation.

The elderly, those 65 years of age and older, will account for 20% of the population by the year 2040. Hypertension affects more than one half of the elderly and its prevalence continues to increase with age. The presence of hypertension confers an increased risk of stroke, congestive heart failure, coronary heart disease, end-stage renal disease, and death. Although both diastolic and systolic blood pressure elevations are independently associated with increased cardiovascular risk in the younger individual, as vascular compliance becomes reduced at age 60, an increasing systolic blood pressure and lower diastolic blood pressure (or wider pulse pressure) increase cardiovascular risk in the elderly. Isolated systolic hypertension is the most common form of hypertension seen in the elderly. Lifestyle modification, including weight loss and salt restriction, reduces blood pressure, and may decrease the need for pharmacologic therapy. When the systolic blood pressure is 160 mm Hg or more and the diastolic blood pressure is <90 mm Hg, the initial use of a diuretic-based or calcium channel blocker-based regimen improves outcome. Alpha blocker therapy should not be used as initial monotherapy. Most elderly hypertensives will require two to three drugs to achieve the present blood pressure goal of <140 mm Hg. Caution should be exercised when lowering diastolic pressure to <55 mm Hg in those with isolated systolic hypertension. Although side effects of therapy are no more likely to occur in the elderly than in the younger individual with hypertension, blood pressure reduction should be accomplished gradually.

Aged↗
PubMedDate not supplied

The effect of a losartan-based treatment regimen on isolated systolic hypertension.

This study was conducted to compare the antihypertensive efficacy and tolerability, over 12 weeks, of a losartan-based treatment regimen and placebo in patients with isolated systolic hypertension. Three hundred eight patients > or =35 years of age with isolated systolic hypertension, defined as trough sitting blood pressure between 140 and 200 mm Hg systolic and between 70 and 89 mm Hg diastolic, were randomized to losartan 50 mg (n=157) or placebo (n=151) once daily, with titration as necessary to achieve a goal trough sitting systolic blood pressure (SBP) <140 mm Hg. At baseline, mean trough sitting SBP was 140-159 mm Hg in 20.5% of patients, 160-179 mm Hg in 62.7%, and 180-200 mm Hg in 16.9%, and was similar in the two groups (losartan, 165.3 mm Hg; placebo, 166.1 mm Hg). At 12 weeks, mean trough sitting SBP decreased significantly (p<0.001) in both the losartan-based treatment group (by 19.2 mm Hg) and in the placebo group (by 7.6 mm Hg). The reduction in sitting SBP was significantly greater for losartan than placebo (-11.6 mm Hg; 95% confidence interval, -14.8 to -8.4). In patients with isolated systolic hypertension, a once-daily losartan-based treatment regimen significantly lowered SBP. The losartan-based regimen exhibited antihypertensive efficacy that was superior to that of placebo, with a similar tolerability profile.

Adult↗
PubMed1996

Out-of-hospital administration of mannitol to head-injured patients does not change systolic blood pressure.

OBJECTIVE: To determine the effect of out-of-hospital mannitol administration on systolic blood pressure (BP) in the head-injured multiple-trauma patient. METHODS: This was a prospective, randomized, double-blind, placebo-controlled clinical trial involving a university-based helicopter air medical service and level-1 trauma center hospital. Endotracheally intubated head-trauma victims with Glasgow Coma Scale (GCS) scores < 12 were enrolled from November 22, 1991, to November 20, 1992, if evaluated by the participating aeromedical transport team within 6 hours of injury. Patients were excluded if they were < 18 years old, had already received mannitol or another diuretic, were potentially pregnant, or were receiving CPR. All patients were intubated prior to study drug (mannitol [1 g/kg] or normal saline) use. Pulse and BP were measured every 15 minutes for 2 hours following study drug administration. RESULTS: A total of 44 patients were enrolled. After exclusion of 3 patients who did not meet all inclusion criteria, there were 20 patients in the mannitol group and 21 patients in the placebo group. The groups were similar at baseline in age, pulse, systolic BP (baseline mannitol: 124 +/- 47 mm Hg; placebo: 128 +/- 32 mm Hg), GCS score, and Injury Severity Scale score. Systolic BP did not change significantly throughout the observation period in either group. This study had 83% power to detect a mean systolic BP drop to < 90 mm Hg. CONCLUSION: Out-of-hospital administration of mannitol did not significantly change systolic BP in this group of head-injured multiple-trauma patients.

Adult↗
PubMedDate not supplied

Systolic time intervals and their derivatives for evaluation of cardiac function.

Systolic time intervals provide a noninvasive indication of global left ventricular performance, are relatively sensitive, and are easily obtained from an M-mode echocardiogram. This paper defines systolic time intervals (preejection period, left ventricular ejection time, and total electromechanical systole) and their derivatives (preejection period/left ventricular ejection time and velocity of circumferential fiber shortening). Their utility and weaknesses, as well as the effects of heart rate, loading conditions, cardiac contractility, and drug therapies on systolic time intervals are discussed. Normal values for systolic time intervals for the dog and cat are provided.

Animals↗
PubMed1991

Diastolic, systolic and sarcoplasmic reticulum [Ca2+] during inotropic interventions in isolated rat myocytes.

1. The fluorescent indicator Fura-2 has been used to monitor intracellular [Ca2+] (Ca2+i) in myocytes isolated from the ventricles of rat hearts. 2. The relationships between diastolic Ca2+i, systolic Ca2+i and the Ca2+ content of the sarcoplasmic reticulum (SR; assayed using caffeine) have been studied during changes of stimulation rate and bathing [Ca2+] (Ca2+o). 3. When stimulation rate was increased, there were increases in diastolic Ca2+i, systolic Ca2+i and the Ca2+ content of the SR. 4. The SR inhibitor ryanodine (1 mumol l-1) decreased the size of the Ca2+i transient, and abolished the increase of Ca2+i produced by caffeine (10 mmol l-1). In the presence of ryanodine, increasing stimulation rate increased diastolic Ca2+i but not systolic Ca2+i. 5. Increasing Ca2+o led to increases of diastolic Ca2+i, systolic Ca2+i and SR Ca2+ content similar to those observed during changes in stimulation rate. 6. Ryanodine altered the relationship between systolic and diastolic Ca2+i during changes of Ca2+o. 7. These results are consistent with a change of diastolic Ca2+i leading to an increase in the Ca2+ content of the SR, and hence an increase in the size of the Ca2+i transient during changes in stimulation rate and Ca2+o.

Animals↗
PubMed1992

The effects of ventricular end-diastolic and systolic pressures on action potential and duration in anaesthetized dogs.

1. Although it is known that mechanical events in the heart influence the duration of the cardiac action potential, there is no quantitative information on the effects of independent changes in ventricular end-diastolic and systolic pressures. 2. Experiments were carried out on open-chest anaesthetized dogs in which the autonomic nervous influences on the heart were prevented and monophasic action potentials were recorded form the epicardial surface of the left ventricle. The duration of these action potentials was taken as the interval from the upstroke to the point of 90% repolarization. 3. Elevation of left ventricular peak systolic pressure, at constant end-diastolic pressure, significantly shortened the monophasic action potential. 4. Elevation of end-diastolic pressure at constant peak systolic pressure significantly lengthened the monophasic action potential. 5. Responses were not dependent on release of noradrenaline from sympathetic nerve terminals because they persisted after administration of bretylium tosylate. They were also not due to myocardial ischaemia because they persisted when coronary perfusion pressure was maintained at a constant high level. 6. Simultaneous recordings of changes in myocardial segment length showed the expected responses to changes in ventricular pressures: increases in shortening in response to increases in diastolic pressure and no consistent effect from changes in systolic pressure. 7. These investigations demonstrate the independent effects of changes in systolic and end-diastolic pressures on cardiac action potential duration. This effect is likely to be an effect of the mechanical events, i.e. contraction-excitation feedback. This response may be mediated through changes in myocardial fibre tension, the consequent changes in fibre shortening, or both.

Action Potentials↗
PubMed2006

Preload maintenance protects against a depression in left ventricular systolic, but not diastolic, function immediately after ultraendurance exercise.

OBJECTIVE: To investigate indices of left ventricular (LV) function before and after a 224 km Ironman triathlon, specifically in the presence of unaltered haemodynamic loading. METHOD: LV loading and function were assessed before and after the race using M mode and Doppler echocardiography in 39 (mean (SD) age 33 (8) years, body mass 77.6 (8.6) kg; 36 male) triathletes in the Trendelenburg position. Specifically left ventricular end diastolic volume (LVEDV) was assessed to estimate preload, and systolic blood pressure to estimate afterload as well as heart rate (HR). Systolic functional indices included ejection fraction (EF) and the end systolic pressure/volume ratio (ESPV), and diastolic functional indices included peak mitral flow velocity in early (E) and atrial (A) filling as well as the ratio E/A. Data obtained before and after the race were compared by t tests, and delta LV functional indices were correlated with delta heart rate. RESULTS: Preload (LVEDV: 143 (34) ml before v 147 (34) ml after) and afterload (systolic blood pressure 121 (13) v 115 (20) mm Hg) were not significantly altered after the race (p>0.05), nor were EF (61 (8)% v 58 (10)%) and ESPV (2.4 (0.9) v 2.1 (0.8) mm Hg/cm(3)). The diastolic filling ratio E/A was significantly reduced after the race (1.73 (0.25) v 1.54 (0.23); p<0.05) due primarily to a reduction in E. HR was significantly higher after the race (57 (9) v 75 (8) beats/min; p<0.05), but delta HR was not related to delta E/A (p>0.05). CONCLUSION: When preload and afterload are unaltered after the race, because of the adoption of a unique assessment posture, LV systolic function is not depressed. A depression in LV diastolic function persists which is not explained by an increase in heart rate after the race.

Adult↗
PubMed1993

Low systolic blood pressure and self perceived wellbeing in middle aged men.

OBJECTIVE: To examine the relation between systolic blood pressure and self perceived wellbeing in 50 year old men. DESIGN: Cross sectional population study of data derived from questionnaires and physical examination as a part of a cardiovascular risk factor survey. SETTING: City of Gothenburg, Sweden. STUDY POPULATION: 776 men from a random population sample of 1016 men aged 50. METHODS: Self perceived wellbeing according to the Gothenburg quality of life questionnaire, which is an assessment of social, physical, and mental wellbeing in 15 different areas. MAIN RESULTS: Low systolic blood pressure was significantly (p < 0.05) related to impaired social wellbeing in four areas: work, home and family, financial situation, and housing. Of the items dealing with physical wellbeing, health, memory, and appetite were significantly related to blood pressure. As regards mental wellbeing, energy and self confidence were significantly related to systolic blood pressure. Diastolic blood pressure was significantly related to housing, memory, energy, patience, and self confidence. In multiple regression analyses that controlled for smoking, stress, physical activity, social activity, and emotional support, poor social, physical, and mental wellbeing were all significantly related to low systolic blood pressure independently of other factors. Low diastolic blood pressure was independently associated with poor physical and mental, but not social, wellbeing. CONCLUSION: Low systolic blood pressure was associated with poor perception of wellbeing in several areas. The cause is unclear.

Attitude to Health↗
PubMed1994

Relation between birth weight at term and systolic blood pressure in adolescence.

OBJECTIVE: To examine whether birth weight is related to systolic blood pressure during adolescence. DESIGN: Retrospective (comparative) cohort study. The observers who traced and studied the subjects were unaware of their case-control status. SUBJECTS: 330 subjects were born in Cardiff in 1975-7. Cases who were low birth weight at term (< 2500 g) were matched with controls of normal birth weight (3000-3800 g) at term. MAIN OUTCOME MEASURES: Systolic blood pressure measured by random zero sphygmomanometry in the subject's right arm with the subject supine, corrected for size and age. RESULTS: The mean age at examination was 15.7 years. The mean systolic blood pressure of the cases was 105.8 mm Hg and of the controls 107.5 mm Hg. The corrected difference (95% confidence interval) in systolic blood pressure between the cases and controls was 1 mm Hg (-3 to +1 mm Hg; two tailed probability 0.33). CONCLUSION: Systolic blood pressure in adolescents of low birth weight is not significantly different from that of adolescents of normal birth weights.

Adolescent↗
PubMed2000

Association of systolic blood pressure with macrovascular and microvascular complications of type 2 diabetes (UKPDS 36): prospective observational study.

OBJECTIVE: To determine the relation between systolic blood pressure over time and the risk of macrovascular or microvascular complications in patients with type 2 diabetes. DESIGN: Prospective observational study. SETTING: 23 hospital based clinics in England, Scotland, and Northern Ireland. PARTICIPANTS: 4801 white, Asian Indian, and Afro-Caribbean UKPDS patients, whether randomised or not to treatment, were included in analyses of incidence; of these, 3642 were included in analyses of relative risk. OUTCOME MEASURES: Primary predefined aggregate clinical outcomes: any complications or deaths related to diabetes and all cause mortality. Secondary aggregate outcomes: myocardial infarction, stroke, lower extremity amputation (including death from peripheral vascular disease), and microvascular disease (predominantly retinal photocoagulation). Single end points: non-fatal heart failure and cataract extraction. Risk reduction associated with a 10 mm Hg decrease in updated mean systolic blood pressure adjusted for specific confounders. RESULTS: The incidence of clinical complications was significantly associated with systolic blood pressure, except for cataract extraction. Each 10 mm Hg decrease in updated mean systolic blood pressure was associated with reductions in risk of 12% for any complication related to diabetes (95% confidence interval 10% to 14%, P<0.0001), 15% for deaths related to diabetes (12% to 18%, P<0.0001), 11% for myocardial infarction (7% to 14%, P<0.0001), and 13% for microvascular complications (10% to 16%, P<0.0001). No threshold of risk was observed for any end point. CONCLUSIONS: In patients with type 2 diabetes the risk of diabetic complications was strongly associated with raised blood pressure. Any reduction in blood pressure is likely to reduce the risk of complications, with the lowest risk being in those with systolic blood pressure less than 120 mm Hg.

Adult↗
PubMed2003

Left ventricular remodelling, and systolic and diastolic function in young adults with beta thalassaemia major: a Doppler echocardiographic assessment and correlation with haematological data.

OBJECTIVE: To evaluate left ventricular morphology and function in a large population of patients with beta thalassaemia. DESIGN: Echo Doppler assessment of left ventricular function and correlation of cardiovascular data with haematological data. SETTING: Thalassaemia unit in a tertiary referral centre. PATIENTS: 197 young adults with beta thalassaemia, following an adequate transfusional and chelation treatment regimen, without clinical signs of cardiopulmonary involvement. The control group consisted of 213 healthy subjects. RESULTS: Left ventricular volumes, mass index, and mass/volume ratio were increased. Diastolic and systolic shapes were different, the left ventricle maintaining an ellipsoidal shape. The ejection fraction was reduced, and was < 50% in 33 patients. Stroke volume and cardiac index were increased, and systemic vascular resistance was decreased. Fractional shortening and mean velocity of circumferential shortening were decreased. Meridional end systolic and peak systolic stress were increased, as was circumferential end systolic stress. The contractile state was reduced while the functional preload index did not differ. Left ventricular diastolic function, evaluated from the mitral inflow, showed a slightly prolonged isovolumic relaxation time, increased flow velocity integrals, and an increased E/A ratio. Among the haematological data, only serum ferritin showed a weak negative correlation with left ventricular ejection fraction. The patients with the highest serum ferritin (> 2500 ng/ml) had the lowest ejection fraction. CONCLUSIONS: Patients with beta thalassaemia on an adequate transfusion and chelation treatment regimen show abnormal left ventricular remodelling with increased volumes, mass, and mass/volume ratio. Systolic chamber function and contractile state are reduced, with a slightly increased afterload. These findings seem mainly to be related to the increased cardiac output caused by chronic anaemia. Left ventricular performance is better preserved when chelation treatment is adjusted to maintain the serum ferritin concentration at < 1000 ng/ml.

Adolescent↗
PubMed2005

Echocardiographic features and brain natriuretic peptides in patients presenting with heart failure and preserved systolic function.

OBJECTIVE: To characterise patients who appear to fulfil the diagnosis of heart failure with preserved systolic function clinically, echocardiographically, and by concentrations of brain-type natriuretic peptide (BNP). METHODS: 102 new cases of heart failure were identified over 24 months in 213 patients referred to a rapid access heart failure clinic. Patients with heart failure and preserved systolic function with contemporary markers of diastolic function were assessed to evaluate their cardiac status further. RESULTS: Forty patients (39%) had an ejection fraction (EF) < 45% and 62 (61%) had an EF > or = 45%. Of these 62 patients, 30 (48%) fulfilled the case definition of diastolic heart failure. The remaining 32 (52%) had neither an EF < 45% nor abnormalities of diastolic function. Dobutamine stress echocardiography was performed on 26 (42%) patients with EF > or = 45%, which provided an alternative explanation for symptoms in 15 (58%) patients. Concentrations of BNP were higher in patients with diastolic abnormalities (mean (SEM) 101.4 (32.5) pg/ml v 58.4 (6.78) pg/ml, p = 0.042) and with no diastolic abnormalities (199 (37.9) pg/ml v 58.4 (6.78) pg/ml, p < 0.0001) than in patients with no heart failure. CONCLUSION: Among ambulatory patients presenting with suspected heart failure in the community 19% have systolic dysfunction, 14% have diastolic dysfunction, and 15% seemingly have heart failure with neither systolic nor diastolic dysfunction. A new understanding, including alternative parameters of diastolic function, seems to be necessary to classify patients with heart failure and preserved systolic function.

Adult↗
PubMed2004

Comparison of simultaneous measurement of mouse systolic arterial blood pressure by radiotelemetry and tail-cuff methods.

Radiotelemetry of mouse blood pressure accurately monitors systolic pressure, diastolic pressure, heart rate, and locomotor activity but requires surgical implantation. Noninvasive measurements of indirect systolic blood pressure have long been available for larger rodents and now are being reported more frequently for mice. This study compared mouse systolic arterial blood pressure measurements using implanted radiotelemetry pressure transducer with simultaneous tail-cuff measurements in the same unanesthetized mice. The pressure range for comparison was extended by inducing experimental hypertension or by observations of circadian elevations between 3 AM and 6 AM. Both trained and untrained tail-cuff operators used both instruments. Every effort was made to follow recommended manufacturer's instructions. With the initial flow-based tail-cuff instrument, we made 671 comparisons (89 sessions) and found the slope of the linear regression to be 0.118, suggesting poor agreement. In an independent assessment, 277 comparisons (35 sessions) of radiotelemetry measurements with the pulse based tail-cuff instrument were made. The slope of the linear regression of the simultaneous measurements of systolic pressures was 0.98, suggesting agreement. Bland-Altman analysis also supported our interpretation of the linear regression. Thus although reliable systolic pressure measurements are possible with either tail-cuff or radiotelemetry techniques, in our hands some tail-cuff instruments fail to accurately detect elevated blood pressures. These data, however, do not distinguish whether this instrument-specific tail-cuff failure was due to operator or instrument inadequacies. We strongly advise investigators to obtain an independent and simultaneous validation of tail-cuff determinations of mouse blood pressure before making critical genotyping determinations.

Animals↗
PubMed1986

End-systolic and end-diastolic ventricular interaction.

Right ventricular volume affects left ventricular volume via direct interaction across the interventricular septum and series interaction because the right and left hearts are connected in series through the lungs. Because it is difficult to sort out complex physiological mechanisms in the intact circulation, the relative importance of these two effects is unknown. We used statistical analyses of transient changes in left and right ventricular pressures and dimensions following pulmonary artery and venae caval constrictions to separate and quantitate the direct (immediate) from the series (delayed) interaction effects on left ventricular size at end systole and end diastole. With the pericardium closed, direct interaction was one-half as important as series interaction at end diastole and was one-third as important at end systole. With the pericardium removed, direct interaction was one-fifth as important as series interaction at end diastole and one-sixth as important at end systole. These results suggest that differences between transient and steady-state end-systolic pressure-volume relationships are largely explained by direct interaction and that direct end-systolic interaction is important for maintaining balanced right and left heart outputs.

Animals↗