Five-year outcome study of deep vein thrombosis in the lower limbs

OBJECTIVE

Venous disease was evaluated in relation to post-thrombotic syndrome 5 years after deep venous thrombosis (DVT) in patients treated with a regimen of low-molecular-weight heparin (LMWH) and warfarin in a Hospital-in-the-Home program.

METHODS

The presence of flow, reflux and compressibility in 51 patients (102 limbs, 54 with DVT and 48 without DVT) was assessed by duplex ultrasound scanning. Blood tests were carried out for prothrombotic screening. Venous disease was related to pathologic severity of post-thrombotic syndrome, characterized by the CEAP (clinical, etiologic, anatomic, pathophysiologic) classification on a scale of 0 to 6.

RESULTS

In the 102 limbs studied, 30 patients (59%) had an underlying thrombophilic disorder. The most common cause of DVT was postoperation and prolonged immobilization not related to postoperation. The most common thrombophilic abnormalities were anticardiolipin antibody and a deficiency of protein C or S, or both. Twenty-six limbs (48%) had proximal involvement (proximal and proximal plus distal DVT); resolution (recanalization or normal vein) in these limbs was seen in 85% at 6 months and 96% at 5 years. After 5 years, 25 of these proximal DVT limbs (96%) developed reflux and there were 4 limbs in CEAP class 0, 8 in classes 1 to 3, and 14 in classes 4 to 6. All of the 28 limbs (52%) with distal DVT showed DVT resolution by 6 months. After 5 years, 10 limbs (36%) developed reflux, and 13 limbs were in class 0, 12 in classes 1 to 3, and 3 limbs in classes 4 to 6. No DVT was detected in the 48 contralateral limbs, but reflux was detected in 25 limbs (52%), predominately in the superficial veins (16 limbs, 64%).

CONCLUSIONS

The resolution of thrombus was more rapid and complete in patients with distal DVT than in those with proximal DVT. Patients with proximal DVT developed a more severe form of post-thrombotic syndrome that was likely related to the development of deep venous reflux. An important finding of this study was an unexpectedly high incidence of venous reflux in the apparently unaffected limb. Although these non-DVT limbs were not investigated at presentation, our data is consistent with the hypothesis that DVT may result in a more systemic disorder of venous function.

Large-artery stiffness contributes to the greater prevalence of systolic hypertension in elderly women

OBJECTIVES

To determine whether sex differences in large-artery stiffness contribute to the greater prevalence of systolic hypertension in elderly women than in elderly men.

DESIGN

During a single visit arterial stiffness was assessed in the unmedicated state using four parameters.

PARTICIPANTS

Three hundred seventy-four women with a mean age+/-standard deviation of 72+/-5 and 296 men aged 71+/-5 participated.

SETTING

Hypertensive patients were recruited from general practice as part of the second Australian National Blood Pressure Study in Melbourne, Australia.

MEASUREMENTS

Large-artery stiffness was assessed using multiple methodologies, including aortic arch stiffness (beta-index) using M-mode ultrasound and arterial compliance and augmentation index using noninvasive carotid pressure and aortic flow measurements.

RESULTS

Women had greater carotid and brachial pulse pressure (PP) than men (P<.001), despite higher mean arterial pressure in men. Mean arterial compliance was lower in women (0.20+/-0.12 vs 0.28+/-0.16 mL/mmHg, P<.001) even after correction for aortic area, and aortic arch stiffness was higher (30+/-36 vs 23+/-22; P<.01). Consistent with both a stiffer proximal circulation and a shorter distance to reflection sites, women had higher augmentation index (38+/-11% vs 29+/-12%, P<.001). In multivariate analysis, sex was an independent determinant of all arterial stiffness indices.

CONCLUSION

Independently of known confounders, elderly hypertensive women have stiffer large arteries, greater central wave reflection, and higher PP than elderly men. Stiffer large arteries likely contribute to the greater prevalence of systolic hypertension in elderly women and may partly explain the acceleration in postmenopausal cerebrovascular and cardiac complications.

Accuracy of automated auscultatory blood pressure measurement during supine exercise and treadmill stress electrocardiogram-testing

OBJECTIVES

Monitoring of brachial blood pressure during exercise-electrocardiogram (ECG) testing is mandatory and changes in blood pressure (BP) can provide critical management evidence. Patient movement, mechanical vibration, artifactual sounds and observer variability make standard manual techniques problematic. This was an investigator-initiated study to assess an automated auscultatory technique of BP assessment [Tango exercise blood pressure monitor (SunTech Medical Instruments, NC, USA)] to adequately measure BP during stress-ECG testing.

METHODS

Initially five fit young male volunteers underwent invasive right brachial artery BP recording using a low-compliance fluid-filled catheter with simultaneous manual and automated assessment. Secondarily, during exercise-ECG testing, the system was assessed against beat-to-beat brachial blood pressures obtained from a catheter-tip solid-state pressure manometer positioned in the ipsilateral brachial artery.

RESULTS

In the supine study overall mean difference (+/-SEM) between invasive and manual blood pressures was 3.26 (1.53) and 3.89 (1.90) mmHg for diastolic BP (DBP) and systolic BP (SBP) respectively. Corresponding differences between invasive and automated results, and manual and automated were 3.68 (0.84) and -7.31 (1.83) mmHg, and -0.64 (+/-1.43) and -11.42 (+/-1.59) mmHg. During treadmill exercise-ECG testing the combined mean difference (+/-SEM) between invasive and automated SBP and DBP was 4.79 (+/-0.14) and 6.33 (+/-0.10) mmHg, respectively.

CONCLUSION

Automated BP assessment during exercise-ECG testing is feasible with the use of appropriate automatic devices likely to be at least as accurate as manual BP registration. The Tango device is tolerant to exercise and provides reliable automatic BP assessment with absolute differences within an acceptable clinical range.

Effect of non-invasive calibration of radial waveforms on error in transfer-function-derived central aortic waveform characteristics

Transfer function techniques are increasingly used for non-invasive estimation of central aortic waveform characteristics. Non-invasive radial waveforms must be calibrated for this purpose. Most validation studies have used invasive pressures for calibration, with little data on the impact of non-invasive calibration on transfer-function-derived aortic waveform characteristics. In the present study, simultaneous invasive central aortic (Millar Mikro-tip® catheter transducer) and non-invasive radial (Millar® Mikro-tip® tonometer) pressure waveforms and non-invasive brachial pressures (Dinamap®) were measured in 42 subjects. In this cohort, radial waveforms were calibrated to both invasive and non-invasive mean and diastolic pressures. From each of these, central waveforms were reconstructed using a generalized transfer function obtained by us from a previous cohort [Hope, Tay, Meredith and Cameron (2002) Am. J. Physiol. Heart Circ. Physiol. 283, H1150–H1156]. Waveforms were analysed for parameters of potential clinical interest. For calibrated radial and reconstructed central waveforms, different methods of calibration were associated with differences in pressure (P<0.001), but not time parameters or augmentation index. Whereas invasive calibration resulted in little error in transfer function estimation of central systolic pressure (difference −1±8 mmHg; P=not significant), non-invasive calibration resulted in significant underestimation (7±12 mmHg; P<0.001). Errors in estimated aortic parameters differed with non-invasively calibrated untransformed radial and transfer-function-derived aortic waveforms (all P<0.01), with smaller absolute errors with untransformed radial waveforms for most pressure parameters [systolic pressure, 5±16 and 7±12 mmHg; pulse pressure, 0±16 and 4±12 mmHg (radial and derived aortic respectively)]. When only non-invasive pressures are accessible, analysis of untransformed radial waveforms apparently produces smaller errors in the estimation of central aortic systolic pressure, and other waveform parameters, than using a generalized transfer function.

Large Artery Stiffness Is Not Related to Plasma Cholesterol in Older Subjects with Hypertension

OBJECTIVE

Previous studies have demonstrated a prognostic role of large artery stiffness in hypertensive subjects and increased stiffness in subjects with coronary artery disease. Although plasma cholesterol is an established risk factor for cardiovascular disease, its relationship with large artery properties in a hypertensive population is unclear.

METHODS AND RESULTS

Plasma cholesterol and large artery properties were measured at baseline in a subset of participants of a randomized controlled trial (ANBP2) evaluating hypertension treatment in older (65 to 84 years) subjects. Noninvasive measures of large artery behavior were central augmentation index (AI), systemic arterial compliance (SAC), and transverse expansion of the aortic arch (aortic distensibility). Arterial waveforms acceptable for analysis were obtained in approximately 80% of cases yielding valid measurements of AI in 868, SAC in 846, and aortic distensibility in 680 subjects. Mean total and high-density lipoprotein (HDL) concentrations were 5.5+/-1.0 and 1.4+/-0.5 mmol L(-1). Total and HDL cholesterol and AI were greater in females than males, whereas SAC and aortic distensibility were greater in males. In multiple regression analyses there were no significant associations between stiffness parameters and total or HDL cholesterol. Significant independent associations in such analyses were found for mean arterial blood pressure, gender, age, height, and heart rate, in keeping with previous findings.

CONCLUSIONS

In the largest cohort of elderly hypertensive subjects studied to date, plasma cholesterol per se was not associated with large artery stiffness. Such independence from cholesterol increases the potential for artery stiffness measurements to additionally contribute to cardiovascular risk assessment in this population.

Use of arterial transfer functions for the derivation of central aortic waveform characteristics in subjects with type 2 diabetes and cardiovascular disease

OBJECTIVE

Optimal blood pressure control in subjects with diabetes reduces cardiovascular complications. There is theoretical benefit in the assessment of central aortic waveforms including the augmentation index, which is taken as a putative index of stiffness. Transfer functions may be used to reconstruct aortic from radial pressure waveforms; however, a single generalized transfer function may not be appropriate for all patients. We aimed to evaluate the technique in subjects with diabetes.

RESEARCH DESIGN AND METHODS

Simultaneous invasive central aortic and noninvasive radial waveforms were acquired in 19 subjects with type 2 diabetes, and a diabetes-specific transfer function was derived. Similar data were acquired from 38 age- and sex-matched subjects without diabetes. Central waveforms were reconstructed using a generalized transfer function in all patients and the diabetes-specific transfer function in individuals with diabetes.

RESULTS

There was no difference between groups in measured central pressures. The error in generalized transfer function-derived systolic pressure was greater in individuals with diabetes (6 +/- 7 mmHg) (mean +/- SD) than without diabetes (2 +/- 8 mmHg) (P<0.05). Errors in other parameters were no different. The diabetes-specific transfer function reduced the error in derived systolic pressure to 0 +/- 7 mmHg in individuals with diabetes--no different than that with the generalized transfer function in individuals without diabetes. The central augmentation index reconstructed by either transfer function was unrelated to that directly measured.

CONCLUSIONS

A generalized transfer function is inappropriate for the derivation of central waveforms in subjects with type 2 diabetes. Errors in subjects with diabetes might be reduced with a diabetes-specific transfer function.

Use of arterial transfer functions for the derivation of aortic waveform characteristics

OBJECTIVE

To investigate the utility and accuracy of radial-aortic arterial transfer functions for the derivation of central blood pressure waveforms. DESIGN Prospective measurement of central and peripheral waveforms in patients undergoing coronary angiography or percutaneous coronary intervention.

METHODS

Simultaneous invasive central aortic and non-invasive radial pressure waveforms were recorded in 78 subjects (61 male : 17 female). Data were applied to a single-input/single-output model for the calculation of a transfer function (TF). Individual TFs were derived by two methods and ensemble averaged TFs obtained for the group. Reverse transformation was performed using each averaged TF applied to the radial data of each subject.

RESULTS

There was close linear correlation between measured aortic parameters and both radial and TF-derived aortic systolic and diastolic pressures (P < 0.001) and most other waveform parameters. However, despite small mean differences between measured and most TF-derived aortic parameters (systolic pressure 0.8-2.9 mmHg, augmentation index 4.3-5.6%), individual scatter was marked, with 95% limits of agreement of +/- 14.6 mmHg (systolic pressure) and +/- 24.4% [augmentation index (AI)]. Indeed, scatter for AI was so marked that measured and derived values were not statistically significantly correlated.

CONCLUSIONS

Transfer functions may be valid for the derivation of some central aortic waveform characteristics. However, in providing neither improved reproducibility nor data on parameters not obtainable from the radial waveform, transfer function techniques may offer no additional clinical benefit. The absence of correlation between measured and TF-derived aortic AI and wide limits of agreement of other parameters should be considered if this technique is utilized in clinical practice.

The aging of elastic and muscular arteries: a comparison of diabetic and nondiabetic subjects

OBJECTIVE

To compare age-related changes in the mechanical properties of different arterial segments in normal volunteers and subjects with type 2 diabetes.

RESEARCH DESIGN AND METHODS

In 169 subjects (diabetic n = 57 and nondiabetic n = 112), we assessed the mechanical properties of three arterial segments of differing wall composition. Pulse wave velocity (PWV) was measured noninvasively in a thoraco-abdominal segment (carotid femoral PWV [PWV(cf)]), in an upper limb muscular artery (carotid radial PWV [PWV(cr)]), and from the aorta to the finger (PWV from the aorta to the finger [PWV(fin)]). Central aortic compliance (CAC) was also measured.

RESULTS

Average CAC was lower (0.662 vs. 0.850, P < 0.05) and all measures of PWV tended to be faster in diabetic subjects despite the fact that they were, on average, 10 years younger. However, these measures were not related to age in diabetic subjects. After correcting for blood pressure, only PWV(cf) was associated with age in nondiabetic subjects (P < 0.001). Expressing results as ratios of nonelastic to elastic arterial segments (i.e., PWV(cr)-to-PWV(cf) and PWV(fin)-to-PWV(cf)) improved the relationship with age. Both PWV(cr)-to-PWV(cf) and PWV(fin)-to-PWV(cf) were significantly associated with age in nondiabetic subjects (r = -0.59, P < 0.001; r = -0.57, P < 0.001) but not in diabetic subjects (r = -0.15, P = 0.302; r = -0.24, P = 0.129). Multivariate analysis showed that the ratios were not associated with systolic blood pressure.

CONCLUSIONS

There are significant differences in the rate of age-related decline in vascular stiffness in elastic arteries of nondiabetic compared with diabetic arteries. Diabetic arteries appear to age at an accelerated rate at an earlier age and then reach a functional plateau.

Comparison of generalized and gender-specific transfer functions for the derivation of aortic waveforms

Arterial transfer functions have been promoted for the derivation of central aortic waveform characteristics not usually accessible noninvasively, but possibly of prognostic significance. The utility of generalized rather than gender-specific transfer functions has not been assessed. Invasive central aortic and noninvasive radial (Millar Mikro-tip tonometer) blood pressure waveforms were recorded simultaneously in 78 subjects (61 male and 17 female). Average transfer functions were obtained for the whole group and for each gender by two methods. Reverse transformation was performed with the use of each transfer function. Measured aortic waveform parameters were compared with those derived using average, gender-appropriate, and gender-inappropriate transfer functions. Differences in central waveform characteristics were demonstrated between men and women. Derived waveform parameters were significantly different from measured values [e.g., subendocardial viability index and augmentation index (P < 0.001)]. A gender-appropriate transfer function significantly improved the derivation of some parameters, including systolic pressure and systolic and diastolic pressure time integrals (P < 0.05). Generalized arterial transfer functions may not be universally applicable across all waveform parameters of potential interest, and gender-specific transfer functions may be more appropriate.

Large artery stiffness predicts ischemic threshold in patients with coronary artery disease

OBJECTIVES

The goal of this study was to determine whether large artery stiffness contributes to exercise-induced myocardial ischemia in patients with coronary artery disease (CAD).

BACKGROUND

Large artery stiffness is an independent predictor of cardiovascular mortality and a major determinant of pulse pressure and, thus, cardiac afterload and coronary perfusion. Clinical relevance of the hemodynamic consequences of large artery stiffening has not previously been demonstrated in relation to myocardial ischemia.

METHODS

We hypothesized that stiffer large arteries would reduce myocardial ischemic threshold as assessed by time to ST-segment depression of 0.15 mV during a treadmill exercise test in patients with CAD. Ninety-six patients with CAD (78 men) age 62 +/- 9 years (mean +/- SD) were classified as having single (52 patients), double (31 patients), or triple (13 patients) coronary vessel disease, based on angiographically confirmed stenoses >50%. Systemic arterial compliance, distensibility index, aortic pulse wave velocity, and carotid augmentation index were measured using carotid applanation tonometry and Doppler velocimetry of the ascending aorta, at rest.

RESULTS

In univariate analysis, all large artery stiffness/compliance indexes correlated with time to ischemia (p = 0.01 to 0.009). Both carotid (p = 0.007) and brachial (p = 0.001) pulse pressure also correlated inversely with time to ischemia. In multivariate analysis including other major risk factors plus severity of coronary stenosis, indexes of arterial stiffness were significant independent predictors of ischemic threshold.

CONCLUSIONS

Within a patient group with moderate CAD, large artery stiffness was a major determinant of myocardial ischemic threshold.

Determinants of coronary artery compliance in subjects with and without angiographic coronary artery disease

OBJECTIVES

The goal of this study was to determine factors contributing to the biomechanical properties of coronary arteries in people with and without angiographic coronary artery disease (CAD).

BACKGROUND

The stiffness of the aorta is known to increase with increasing age and in the presence of CAD. However, little is known about the mechanics of coronary arteries, which may have important clinical consequences.

METHODS

Intravascular ultrasound was used to determine the mechanical properties of coronary arteries and plaque behavior in subjects with CAD (n = 38), those with chest pain but angiographically normal coronary arteries (N) (n = 9) and those early (<2 weeks) after cardiac transplant (T) (n = 14).

RESULTS

Coronary arteries dilated during systole in all groups, but cross-sectional compliance and distensibility were lowest in the proximal left anterior descending artery (LAD) in the subjects with CAD compared with the N and T groups (compliance: 1.2 +/- 0.2 vs. 1.7 +/- 0.5 and 2.7 +/- 0.6 x 10(-2) mm(2) mm Hg(-1) [mean +/- SEM] respectively, p < 0.02 CAD vs. T; distensibility: 0.8 +/- 0.2 vs. 1.7 +/- 0.5 and 1.7 +/- 0.3 x 10(-3) mm Hg(-1), p < 0.05 CAD vs. T). There was extensive plaque in the CAD group, and plaque was also present in the N group, but minimal atheroma was present in the T group. Plaque cross-sectional area diminished significantly during systole in both the LAD and circumflex arteries. Absolute changes were: 0.50 +/- 0.30, 0.33 +/- 0.11 and 0.68 +/- 0.13 mm(2) in the proximal LAD, distal LAD and proximal circumflex arteries, respectively. In subjects with atheroma, there was a significant correlation between cross-sectional compliance and plaque compression at all sites, and plaque compression was a significant determinant of cross-sectional compliance at both proximal sites in multiple regression analyses with age, mean arterial pressure and extent of plaque as the other independent variables.

CONCLUSIONS

A major determinant of the systolic increase in coronary luminal area in patients with atheroma is a reduction in plaque cross-sectional area during systole.

Intensive cholesterol reduction lowers blood pressure and large artery stiffness in isolated systolic hypertension

OBJECTIVES

We sought to investigate the effects of intensive cholesterol reduction on large artery stiffness and blood pressure in normolipidemic patients with isolated systolic hypertension (ISH).

BACKGROUND

Isolated systolic hypertension is associated with elevated cardiovascular morbidity and mortality and is primarily due to large artery stiffening, which has been independently related to cardiovascular mortality. Cholesterol-lowering therapy has been efficacious in reducing arterial stiffness in patients with hypercholesterolemia, and thus may be beneficial in ISH.

METHODS

In a randomized, double-blinded, cross-over study design, 22 patients with stage I ISH received three months of atorvastatin therapy (80 mg/day) and three months of placebo treatment. Systemic arterial compliance was measured noninvasively using carotid applanation tonometry and Doppler velocimetry of the ascending aorta.

RESULTS

Atorvastatin treatment reduced total and low-density lipoprotein cholesterol and triglyceride levels by 36 +/- 2% (p < 0.001), 48 +/- 3% (p < 0.001) and 23 +/- 5% (p = 0.003), respectively, and increased high density lipoprotein cholesterol by 7 +/- 3% (p = 0.03). Systemic arterial compliance was higher after treatment (placebo vs. atorvastatin: 0.36 +/- 0.03 vs. 0.43 +/- 0.05 ml/mm Hg, p = 0.03). Brachial systolic blood pressure was lower after atorvastatin treatment (154 +/- 3 vs. 148 +/- 2 mm Hg, p = 0.03), as were mean (111 +/- 2 vs. 107 +/- 2 mm Hg, p = 0.04) and diastolic blood pressures (83 +/- 1 vs. 81 +/- 2 mm Hg, p = 0.04). There was a trend toward a reduction in pulse pressure (71 +/- 3 vs. 67 +/- 2 mm Hg, p = 0.08).

CONCLUSIONS

Intensive cholesterol reduction may be beneficial in the treatment of patients with ISH and normal lipid levels, through a reduction in large artery stiffness.