Intra-arterial Pressure Research Articles

Diurnal variation of hemodynamic indices in non-dipper hypertensive patients.

The purpose of this study was to elucidate the underlying mechanisms of blunted nocturnal blood pressure reduction in non-dipper hypertensive patients. We studied the diurnal variations in systemic hemodynamic indices and baroreflex sensitivity. In 45 subjects with essential hypertension (24 men; mean age, 49+/-1 years), intra-arterial pressure was monitored telemetrically. Non-dippers were defined as those with a nocturnal reduction of systolic blood pressure of less than 10% of daytime systolic blood pressure. Stroke volume was determined using Wesseling's pulse contour method, calibrated with indocyanine green dilution. Baroreflex sensitivity was calculated as deltapulse interval/deltasystolic blood pressure on spontaneous variations. The mean values of the hemodynamic parameters were calculated every 30 min. Twenty-six subjects were classified as non-dippers. Daytime blood pressure was not significantly different between dippers (149+/-4/87+/-3 mmHg) and non-dippers (147+/-3/82+/-2 mmHg), while the nighttime blood pressure was significantly reduced in dippers (131+/-3/77+/-2 mmHg) but not in non-dippers (145+/-3/80+/-2 mmHg). Nocturnal decreases in both cardiac index and stroke index were smaller in non-dippers (-12.0+/-1.2% and 1.5+/-1.0%) than in dippers (-17.5+/-1.4% and -2.2+/-1.1%). Baroreflex sensitivity significantly increased at nighttime both in dippers (6.5+/-0.6 to 8.0+/-0.7 ms/mmHg) and in non-dippers (5.1+/-0.3 to 6.4+/-0.4 ms/mmHg). Neither daytime nor nighttime baroreflex sensitivity was significantly different between the groups. We conclude that the hemodynamics of non-dipper essential hypertension are characterized by an inadequate nocturnal decrease in cardiac index and stroke index, suggestive of relative volume expansion or malsuppressed sympathetic activity.

Pulse oximeter waveform analysis as a measure of circulatory status

The pulse oximeter waveform (POW) is derived from variation in intensity of transmitted light through tissues. It may be used to provide a non-invasive surrogate for the intra-arterial waveform, and represents an accessible measure of cardiovascular status. We examined the effects of age, blood pressure and smoking on the waveform patterns. These factors are known to decrease arterial compliance, increase peripheral wave reflection and alter the contour of the pulse pressure waveform. Supine and standing POW recordings were taken from 200 healthy volunteers. The resting waveform patterns were categorised into four distinct classes as described by Murgo and Nichols for intra-arterial pressure waveforms, and compared to age and systolic blood pressure. Post hoc ANOVA revealed a significant relationship between waveform class and age (P < 0.001), blood pressure (P < 0.001), and smoking status (P = 0.021. These effects appear to represent changes in the peripheral arterial system resulting from altered wave reflection. We also analysed the POW in both time and frequency domains. On standing, time domain analysis showed a decrease in total variability, as measured by standard deviation and variance. Frequency domain analysis demonstrated an increase in power at a frequency (0.1 Hz) associated with sympathetic nervous system output. These results are consistent with changes in the microcirculation related to autonomic control mechanisms. These patterns of change, however, were only apparent in a proportion of the subjects. We believe that the responses elicited are dependent on factors affecting the long-term compliance of the arterial tree, and are thus related to the pulse oximeter waveform classification described. We have shown that POW analysis yields consistent and reproducible patterns. Further research may lead to the use of these techniques as a measure of peripheral vascular responsiveness, with potential utility in the evaluation of cardiovascular disease.

Transient hypertension directly impairs endothelium-dependent vasodilation of the human microvasculature.

Hypertension is associated with decreased endothelium-dependent vasodilation. However, whether endothelial dysfunction is a cause or a consequence of elevated blood pressure is unknown. Therefore, to determine whether hypertension can directly induce endothelial dysfunction, we investigated the effect of increases in intra-arterial pressure on endothelium-dependent vasodilation of the human microvasculature. Small arteries (internal diameter 202+/-75 micrometer) were isolated from gluteal fat biopsies in 12 healthy normotensive subjects (8 men and 4 women; age, 46+/-10 years). Arteries were cannulated and perfused in chambers oxygenated at 37 degrees C. Endothelium-dependent and -independent responses to acetylcholine (Ach; 10(-9) to 10(-4) mol/L) and sodium nitroprusside (SNP; 10(-9) to 10(-4) mol/L), respectively, were obtained after incubating the vessel with incremental intravascular pressures of 50, 80, and 120 mm Hg for 60 minutes each. The response to Ach was also obtained in different arteries after 3 consecutive incubation periods at 50 mm Hg. Arterial internal diameter was measured directly from amplified digital images. A significant reduction in the vasodilator response to Ach was observed with increases in intravascular pressure (mean vasodilation, 62%, 49%, and 26% at 50, 80, and 120 mm Hg, respectively; P<0.001). In contrast, the response to SNP showed a nonsignificant trend toward greater vasodilation with increases in pressure (mean vasodilation, 40%, 52%, and 57% at 50, 80, and 120 mm Hg, respectively; P=0.10). There was no difference in the consecutive dose-response curves to Ach obtained at the same intravascular pressure (mean vasodilation: 48%, 46%, and 49%; P=0.61). Transient increases in intravascular pressure significantly depress endothelium-dependent vasodilation in human resistance arteries. These findings suggest that elevated blood pressure per se may cause endothelial dysfunction in humans and have implications for the pathophysiology of endothelial dysfunction in hypertension.

Diagnostic evaluation of aortoiliac occlusive disease: when is a lesion significant?

Many methods, both invasive and noninvasive, are currently available for evaluation of the aortoiliac arterial system before and after percutaneous intervention. Optimal evaluation requires a combination of morphologic and functional information to localize, characterize, and assess the hemodynamic significance of any primary or residual arterial narrowing. In this article, we consider these methods, with an emphasis on the combination of contrast arteriography and intra-arterial pressure measurements in current management of aortoiliac disease.

Dietary magnesium intake can affect mechanical properties of rat carotid artery

The purpose of the present study was to determine the effects of Mg deficiency and supplementation on the mechanical properties of the rat common carotid artery. The internal diameter and intra-arterial pressure of carotid artery were measured continuously using an echo-tracking device. Systolic, diastolic and mean intra-arterial pressures were not significantly different in Mg-deficient, -supplemented or control rats. Histological examination showed a larger cross-sectional area, increased intima-media thickness and a greater media:lumen value in carotid artery of Mg-deficient rats, indicating that Mg deficiency may directly stimulate growth and/or proliferation of arterial wall components. In addition, we observed a negative linear relationship between intima-media thickness and plasma Mg concentration, suggesting that increased Mg intake may counteract arterial wall hypertrophy. Neither Mg deficiency nor supplementation modified the arterial distensibility v. intra-arterial pressure curve or the E(inc) v. wall stress curve, indicating that dietary Mg intake did not modify wall stiffness in young rats. At mean intra-arterial pressure, the stress and E(inc) values were, however, significantly lower in Mg-deficient rats (p < 0.05 in both cases); this finding could be related to the alteration in the geometry of the carotid artery. In conclusion, these findings suggest that Mg deficiency modifies the mechanical properties of the common carotid artery in young rats. Since Mg deficiency is considered a risk factor, these mechanical alterations could contribute to the development of atherosclerosis, hypertension and cardiovascular diseases.

An evaluation of a new continuous blood pressure monitoring system in critically ill patients

Study Objective: To determine if the DxTek monitor, which is a device that measures blood pressure (BP) noninvasively and continuously by means of pulse velocity and wave shapes derived from the pulse oximeter optical plethysmograph and electrocardiogram is as accurate as an oscillometric cuff device when compared with intraarterial BP measurement. Design: Prospective, comparative study. Setting: University Medical Center. Patients: 28 intensive care unit patients. Interventions: Blood pressures were reported every minute by intraarterial catheters and DxTek and every 10 minutes by an oscillometric monitor for 2 to 5 hours. DxTek calibration was performed initially and when specified patient manipulations by caretakers were performed (on average, every 100 minutes). Comparisons with intraarterial pressure included: 1) DxTek calibrated with arterial catheter pressure, 2) DxTek calibrated with oscillometric pressure, and 3) oscillometric pressure. Measurements and Main Results: When comparing oscillometric pressure to intraarterial pressure, the averages of the mean differences (bias) were −4.0 mmHg for systolic (SBP) and < 1.5 mmHg for diastolic (DBP) and mean (MAP) pressures. The averages of the standard deviation of the differences (precisions) were 9.6, 6.4, and 6.3 mmHg, respectively. With the DxTek device calibrated to intraarterial pressure, comparison of the DxTek pressure to intraarterial pressure resulted in a bias ≤0.5 mmHg for all three pressures and an average precision of 10.1 mmHg for SBP, 6.0 mmHg for DBP, and 6.7 mmHg for MAP. With the DxTek device calibrated to the oscillometric pressure, the DxTek pressure compared to the intraarterial pressure resulted in average biases of −5.1, −0.8, and −2.2 mmHg and average precisions of 11.1, 7.7, and 8.1 mmHg for SBP, DBP, and MAP, respectively. Conclusions: The DxTek monitor provides continuous, noninvasive BP measurements with an accuracy comparable to oscillometric devices.

Long-term central hemodynamic effects at rest and during exercise of losartan in essential hypertension

Background Losartan reduces blood pressure in patients with essential hypertension, but the long-term central hemodynamic effects at rest and during exercise are not known. Methods and Results After 8 months of losartan treatment (50 to 100 mg daily, mean 82 mg), intra-arterial pressure was reduced from 165/102 mm Hg to 145/91 mm Hg at rest and from 193/104 mm Hg to 179/96 mm Hg during 100 W exercise in 28 patients with essential hypertension. Cardiac index and heart rate remained unchanged, but total peripheral resistance index was reduced 12% to 15%. Stroke index was unchanged at rest but increased 7% to 9% during exercise. Twenty-four-hour ambulatory blood pressure was reduced 10% to 13%. Left ventricular mass was reduced 27% in patients with left ventricular hypertrophy (n = 18). Conclusion Losartan lowers blood pressure by reducing total peripheral resistance at rest and during exercise but cardiac pump function is unchanged or slightly improved. In patients with left ventricular hypertrophy, losartan induces a sizeable reduction in left ventricular mass. (Am Heart J 2000;140:624-30.)

High blood pressure and the kidney: The forgotten contribution of William Senhouse Kirkes

The realization of the key role for raised intra-arterial pressure as a pathogenetic agent in hypertension is usually credited to Ludwig Traube, but Traube in his writings gives credit for the idea to a little-known English doctor, William Senhouse Kirkes (1822-1864). Kirkes' main interest was in cardiology and vascular disease, and he gave the first account of embolism from vegetations in infective endocarditis in 1852. Three years later, he published a study of apoplexy in Bright's disease, in which he pointed clearly to the role of raised intra-arterial tension in the causation of arterial disease, a point that had eluded Bright, Johnson, and other contemporaries. Kirkes died at the age of only 42 while working on a book summarizing his work on cardiology and renal disease, and the neglect of his contribution probably resulted from his early death. We have traced his life history from the few available records; as a boy, Kirkes was apprenticed to become a surgeon and only later trained as a physician. We place his contributions within the setting of the development during the 19th century of understanding of the relationship between the kidney, vascular disease, and high blood pressure.

Invited commentary

The authors assessed the outcome of the Allen’s test compared with the use of the Doppler ultrasound test of the ulnar collateral circulation. They regard the Doppler ultrasound examination of triphasic wave form in the princeps pollicis artery as the “gold standard.” The concerns we have are, firstly, regarding the acceptance of the wave form of the Doppler ultrasound as a gold standard in the assessment of the hand collateral circulation. Baxter and his colleagues [1Baxter BT, Blackburn D, Payne K, Pearce WH, Yao JS. Noninvasive evaluation of the upper extremity. Surg Clin N Am 1990;70:87–97.Google Scholar] state in relation to this test “that the wave form characteristics do not correlate accurately with disease when measured with direct intra-arterial pressure and angiography.”Secondly, the main concern with the Allen’s test is that it may provide a false negative result, thus allowing the surgeon to harvest the artery in a situation where the ulnar collateral circulation is inadequate. The Doppler ultrasound and the digital systolic blood pressure measurements only register the changes occurring immediately following the occlusion of the radial artery and do not provide any information about the subsequent return of the collateral circulation through various compensatory mechanisms. The authors have found that using the Allen’s test with a cut-off point of five seconds results in a false negative rate of 24% (8 of 33). We also found a good correlation between the time of recovery using the Allen’s test compared with the systolic blood pressure in the thumb after occlusion of the radial artery. We concluded that the time of recovery by the Allen’s test of eight seconds achieved the maximum Youden’s index (similar to the ROC curve) and produced a more acceptable false negative rate of 18%.In our unit, 1,500 patients have proceeded to radial artery harvest based on the normal Allen’s test and experienced no complications. Our current recommendation, then, is to perform Doppler ultrasound on all patients who have a positive (abnormal) Allen’s test to prevent those patients, from whom it would be safe to remove the radial artery, being excluded from radial artery harvesting. The authors assessed the outcome of the Allen’s test compared with the use of the Doppler ultrasound test of the ulnar collateral circulation. They regard the Doppler ultrasound examination of triphasic wave form in the princeps pollicis artery as the “gold standard.” The concerns we have are, firstly, regarding the acceptance of the wave form of the Doppler ultrasound as a gold standard in the assessment of the hand collateral circulation. Baxter and his colleagues [1Baxter BT, Blackburn D, Payne K, Pearce WH, Yao JS. Noninvasive evaluation of the upper extremity. Surg Clin N Am 1990;70:87–97.Google Scholar] state in relation to this test “that the wave form characteristics do not correlate accurately with disease when measured with direct intra-arterial pressure and angiography.” Secondly, the main concern with the Allen’s test is that it may provide a false negative result, thus allowing the surgeon to harvest the artery in a situation where the ulnar collateral circulation is inadequate. The Doppler ultrasound and the digital systolic blood pressure measurements only register the changes occurring immediately following the occlusion of the radial artery and do not provide any information about the subsequent return of the collateral circulation through various compensatory mechanisms. The authors have found that using the Allen’s test with a cut-off point of five seconds results in a false negative rate of 24% (8 of 33). We also found a good correlation between the time of recovery using the Allen’s test compared with the systolic blood pressure in the thumb after occlusion of the radial artery. We concluded that the time of recovery by the Allen’s test of eight seconds achieved the maximum Youden’s index (similar to the ROC curve) and produced a more acceptable false negative rate of 18%. In our unit, 1,500 patients have proceeded to radial artery harvest based on the normal Allen’s test and experienced no complications. Our current recommendation, then, is to perform Doppler ultrasound on all patients who have a positive (abnormal) Allen’s test to prevent those patients, from whom it would be safe to remove the radial artery, being excluded from radial artery harvesting.

Noninvasive evaluation before and after percutaneous therapy of iliac artery stenoses: The value of the Bernoulli-predicted pressure gradient

Purpose: The purpose of this study was to assess the value of the Bernoulli-predicted pressure gradient in the noninvasive evaluation of patients undergoing iliac percutaneous transluminal angioplasty (PTA) or stent placement with the use of intra-arterial pressure measurements as the standard of reference. Methods: Stent placement or PTA was performed in 261 patients with intermittent claudication caused by iliac artery stenoses (333 procedures). Intra-arterial translesional pressure gradients were recorded before and after each procedure. Hemodynamic success was defined as a postprocedural mean pressure gradient less than or equal to 10 mm Hg at rest and during vasodilatation. Before and after intervention, the following noninvasive parameters were determined: the Bernoulli-predicted pressure gradient, the peak systolic velocity ratio, and the ankle-brachial pressure index. Results: Before treatment, both the intra-arterial–measured pressure gradients and the Bernoulli-predicted gradients indicated hemodynamic significance of the iliac artery stenoses. After treatment, both methods indicated significant improvement of the translesional pressure gradient (P <.0001). However, the correlation between the intra-arterially measured pressure gradient and the Bernoulli-predicted gradient of iliac artery stenoses was low (Pearson's r = 0.27). None of the three investigated noninvasive methods could differentiate an optimal PTA or stent result from a suboptimal result, as assessed by intra-arterial pressure measurements. Conclusions: The disappointing correlation among the duplex velocity data, whether expressed as pressure gradient or as a peak systolic velocity ratio, and the actually measured pressure gradient might be caused by errors in pressure or velocity measurements or the different circumstances in which the pressure or velocity measurements were performed. Residual pressure gradients after iliac PTA or stent placement assessed with intra-arterial pressure measurements could not be assessed with the investigated noninvasive methods. (J Vasc Surg 2000;32:153-9.)

Gadolinium-enhanced Magnetic Resonance Angiography, Digital Subtraction Angiography and Duplex of the Iliac Arteries Compared with Intra-arterial Pressure Gradient Measurements

Purpose: to compare gadolinium-enhanced magnetic resonance angiography (Gd-MRA), digital subtraction angiography (DSA) and duplex of the iliac arteries with intra-arterial pressure gradient measurement as the reference method. Materials and methods: Gd-MRA, DSA and duplex examinations of the iliac arteries were performed in 30 patients (60 arteries) with lower-limb arterial occlusive disease. In 29 arteries, pressure measurements were made (n=25) or the artery was found to be occluded on catheterisation (n=4). An aortofemoral peak systolic pressure gradient of 20 mmHg or more was regarded as haemodynamically significant. Stenoses with a diameter reduction of 50% or more on MRA or DSA, or an increase in peak systolic velocity greater than 150% (duplex) were considered significant. MRA examinations were evaluated by means of maximum intensity projections (MRA-MIP) and using source images and curved multiplanar reconstruction (MRA-MPR). Results: the sensitivity (specificity) for a significant iliac artery stenosis were 81% (75%) for MRA-MIP, 76% (75%) for MRA-MPR, 86% (88%) for DSA, and 72% (88%) for duplex. Conclusion: with intra-arterial pressure measurements as the reference method, similar results were achieved with Gd-MRA, DSA and duplex concerning the detection of haemodynamically significant iliac artery stenoses. The use of source images and multiplanar reconstructions resulted in higher accuracy for the detection of occlusions.

Combined regional and general anesthesia for orthopedic spine fusion surgery

The combination of epidural anesthesia and general anesthesia is a sophisticated technique that offers many advantages for the patient undergoing lumbar spine fusion. With a proper understanding of the physiological and pharmacological considerations of this technique, it can be used to aggressively lower blood pressure intraoperatively, minimizing blood loss and maximizing the condition of the surgical field. Optimal postoperative pain management can be achieved with minimal side effects. The circulatory and cardiac effects of epidural hypotension must be appreciated before embarking on the use of this technique. The extensive sympathetic blockade achieved must be controlled by support of the circulation with an infusion of epinephrine. The technique involves a combination of a high-level epidural anesthetic using bupivacaine or ropivacaine. For safety, this is started before the induction of general anesthesia. Continuous monitoring of both intraarterial and central venous pressures must be performed to avoid precipitous hypotension and sudden bradycardia. Mean arterial pressure is targeted and controlled in the 50 to 60 mm Hg range. A light, general anesthetic with a nitrous narcotic technique is used to supplement the epidural. Epidural anesthesia alone has been found to diminish intraoperative blood loss by significant volumes. Epidural hypotensive anesthesia with proper technique further reduces blood loss, decreases the incidence of deep venous thrombosis, and is associated with an extremely low complication rate. This has been shown by numerous studies on patients who had total hip arthroplasties. Extensive epidural anesthesia applied to lumbar spine fusion surgery theoretically can achieve these same advantageous outcomes. Copyright © 2000 by W.B. Saunders Company

Oscillatory patterns in sympathetic neural discharge and cardiovascular variables during orthostatic stimulus.

We tested the hypothesis that a common oscillatory pattern might characterize the rhythmic discharge of muscle sympathetic nerve activity (MSNA) and the spontaneous variability of heart rate and systolic arterial pressure (SAP) during a physiological increase of sympathetic activity induced by the head-up tilt maneuver. Ten healthy subjects underwent continuous recordings of ECG, intra-arterial pressure, respiratory activity, central venous pressure, and MSNA, both in the recumbent position and during 75 degrees head-up tilt. Venous samplings for catecholamine assessment were obtained at rest and during the fifth minute of tilt. Spectrum and cross-spectrum analyses of R-R interval, SAP, and MSNA variabilities and of respiratory activity provided the low (LF, 0.1 Hz) and high frequency (HF, 0.27 Hz) rhythmic components of each signal and assessed their linear relationships. Compared with the recumbent position, tilt reduced central venous pressure, but blood pressure was unchanged. Heart rate, MSNA, and plasma epinephrine and norepinephrine levels increased, suggesting a marked enhancement of overall sympathetic activity. During tilt, LF(MSNA) increased compared with the level in the supine position; this mirrored similar changes observed in the LF components of R-R interval and SAP variabilities. The increase of LF(MSNA) was proportional to the amount of the sympathetic discharge. The coupling between LF components of MSNA and R-R interval and SAP variabilities was enhanced during tilt compared with rest. During the sympathetic activation induced by tilt, a similar oscillatory pattern based on an increased LF rhythmicity characterized the spontaneous variability of neural sympathetic discharge, R-R interval, and arterial pressure.

High blood pressure and the kidney: The forgotten contribution of William Senhouse Kirkes

High blood pressure and the kidney: The forgotten contribution of William Senhouse Kirkes

Quantification of hemodynamic improvement after superficial femoral artery angioplasty by cine phase contrast MR angiography.

peripheral vascular disease on blood flow are made from indirect measurements such as morphologic assessment of stenosis on angiograms, Doppler velocities, or the ankle-brachial index. However, the correlation of the severity of morphologic stenosis with catheter angiography and hemodynamic significance can be difficult [I]. Intraarterial pressure recordings obtained at the time of catheter angiography have been considered the gold standard to assess the hemodynamic effect of stenoses, but the definition of a significant pressure gradient remains controversial [2]. The most widely used noninvasive method of vascular assessment is Doppler sonography. Flow measurements can be obtained by measuring cardiac rate, velocities, and blood vessel cross-sections; however, in a previous study the latter were prone to considerable observer variability [3]. Peripheral vascular assessment by Doppler sonography is limited in regions that have overlying bowel or adjacent cortical bone, and differentiation between a stenosis and occlusion may be problematic when welldeveloped collaterals are present. Techniques such as venous occlusion p1ethysmography that directly measure blood flow reveal that exercise flow correlates well with the severity of occlusive disease, but resting blood flow does not [4]. However, venous occlusion plethysmography has proved awkward for clinical use. Peripheral MR angiography using timeof-flight and gadolinium techniques now rivals catheter angiography for routine assessment of the peripheral vasculature [5] but is subject to the same morphologic limitations in stenosis assessment as catheter angiography. Previous studies have shown that cine phase contrast MR angiography can accurately quantify resting and exercise flow in the lower extremity [4] and can also quantify renal blood flow before and after angioplasty [6]. The addition of this sequence to routine MR angiography would provide important physiologic information with respect to stenoses. To evaluate the feasibility of using cine phase contrast MR angiography for this evaluation, we quantified the improvement in arterial blood flow after exercise in the superficial femoral artery before and after perFig. 1.-Drawing shows superficialfemoral artery stenosis and three flow sampling levels (samples 1. 2. and 3). (Courtesy of Bromley P, Vancouver, B. C., Canada)

Similar Central Hemodynamics in Salt-sensitive and Salt-resistant Hypertensive Patients

Salt may be involved in the pathogenesis of essential hypertension but no agreement has been reached on how salt might exert its blood pressure control. One reason for the conflicting results could be differences in response to changes in salt intake--i.e. between salt-sensitive and salt-resistant subjects. Hypertension reflects a hemodynamic disturbance: mainly an increase in total peripheral resistance. In order to determine whether central hemodynamics is different in salt-sensitive and salt-resistant essential hypertension, a study was carried out on 37 patients aged 31-63 years with mean casual blood pressure 165/104 mmHg. Based on an increase in ambulatory 24-h mean blood pressure of > or = 10% after one week of dietary salt loading (260 mmol NaCl/24 h) following a one-week salt depletion period (60 mmol NaCl/24 h), 7 patients (19%) were classified as salt sensitive and 30 patients (81%) as salt resistant. Before the salt-sensitivity test, while patients were on their habitual salt intake (160 mmol NaCl/24 h), central hemodynamics (intra-arterial pressure, cardiac output by dye dilution, heart rate by electrocardiogram, and total peripheral resistance) was examined at rest and during bicycle exercise. None of the central hemodynamic variables were different between the two groups, despite a marked difference in blood pressure response to one week of salt loading between the salt-sensitive and the salt-resistant groups (27/9 mmHg vs -2/1 mmHg). Furthermore, no statistically significant differences were observed in neurohumoral variables or echocardiographic indices of left ventricular dimensions between the two groups. Owing to the invasive hemodynamic procedure, central hemodynamics was not restudied during high- or low salt intake. It is concluded that there is no difference in central hemodynamics in salt-sensitive and salt-resistant hypertensive patients when they are on their habitual salt diet.

Large artery structure and function in hypertension and end-stage renal disease.

The cardiovascular complications in hypertension are ascribed to two different but associated alterations, namely atherosclerosis and arteriosclerosis. Whereas the former disturbs principally the conduit function and the delivery of an adequate blood flow to peripheral organs and tissues, the latter disturbs the cushioning function of large arteries, inducing an inadequate increase in systolic and pulse pressure. Arteriosclerosis represents a clinical form of accelerated ageing process and is characterized by a diffuse dilation and hypertrophy of large conduit arteries and stiffening of arterial walls. Independently from the ageing, structural changes are associated with several haemodynamic alterations such as increased in blood flow and flow velocity, and increased parietal stress due to increased arterial diameters and/or intraarterial pressure. The principal consequences of arterial stiffening are: (1) an increased left ventricular afterload with development of left ventricular hypertrophy and increased myocardial oxygen demand; (2) altered coronary perfusion and blood flow distribution; and (3) decreased perfusion reserve during haemodynamic stress. In the absence of controlled studies, it is difficult to propose therapeutic interventions aimed to prevent or treat arterial abnormalities in hypertensive patients. It has been shown that long-term administration of either calcium channel blockers and angiotensin converting enzyme inhibitors led to an improvement of vessel wall elasticity. Nevertheless, these studies did not conclude whether the improvement of elastic properties were due only to decrease in blood pressure or to alterations in intrinsic properties of arterial walls. More investigations should be necessary to investigate this important problem.

Comparison of Iotrolan 320 and Iohexol 350 in cardiac angiography: a randomised double-blind clinical study

Objective: A double-blind randomised study was conducted in two British centres, to evaluate the safety, tolerance and efficacy of the new dimeric non-ionic contrast medium Iotrolan 320 in comparison with the monomeric non-ionic compound Iohexol 350 in coronary angiography. Methods and Material: 120 patients were randomised to receive either Iotrolan at a concentration of 320 mgI/ml or Iohexol at a concentration of 350 mgI/ml, during selective coronary angiography and left ventriculography. The variables measured were: maximum increase of the left ventricular end-diastolic pressure up to 6 min after ventriculography, haemodynamic and electrocardiographic variables, arrhythmogenicity, clinical laboratory parameters, tolerance, adverse events and efficacy. Results: Iotrolan resulted in a smaller change of left ventricular end-diastolic pressure compared to Iohexol, but the difference was not statistically significant. Transient changes in left ventricular systolic pressure, intra-arterial systolic pressure, intra-arterial diastolic pressure, and in electrocardiographic parameters, occurred after the injections, but they were not clinically significant. Changes in the clinical laboratory markers from baseline values were comparable between the two groups and confirmed good renal and hepatic tolerance. During the left ventriculogram, Iotrolan resulted in less symptoms compared to Iohexol ( P=0.002). Adverse events, which were mild or moderate in most cases, were observed with no statistical difference between the two agents. The contrast quality of both agents was good with no statistical difference. Conclusion: This study did not show a significant difference between Iotrolan 320 and Iohexol 350 with regard to cardiovascular safety or patient tolerance, except for a minor difference in the intensity of heat/warmth sensation.

Randomised trial of management of hypertensive pregnancies by Korotkoff phase IV or phase V

There is debate about whether diastolic blood pressure should be recorded as the fourth (muffling, K4) or fifth (disappearance, K5) Korotkoff sound in pregnancy. We compared maternal and fetal outcomes and the likelihood that episodes of severe hypertension would be recorded when hypertensive pregnancies were managed according to either K4 or K5. 220 pregnant women with diastolic hypertension (K4 > or =90 mm Hg) after the 20th week of gestation were enrolled in a prospective randomised study at two obstetric units in Australia; they were randomly assigned management with K4 (n=103) or K5 (n=117) for the remainder of the pregnancy. Clinical management was according to a uniform department protocol. Analysis was by intention to treat. All the women completed the trial. An episode of severe hypertension (systolic > or =170 mm Hg, diastolic > or =110 mm Hg, or both) was more likely to be recorded with use of K4 than with use of K5 (39 [38%] vs 30 [26%] women, p=0.051), mainly because of a greater likelihood that severe diastolic hypertension would be recorded (34 [33%] vs 20 [17%], p=0.006). The frequency of severe systolic hypertension and simultaneous severe systolic and diastolic hypertension did not differ between groups. Pregnancy was prolonged by an average of 2 weeks in both groups, and there were no significant differences between the groups in laboratory data, requirements for antihypertensive treatment, birthweight, fetal growth retardation, or perinatal mortality. There was no eclampsia or significant maternal morbidity in either group. A change from use of K4 to K5 would mean that one fewer case of severe diastolic hypertension would be recorded for every six hypertensive pregnancies, but all other episodes of severe hypertension would be recorded with similar frequency. Since the K4/K5 difference is smaller in hypertensive than in normotensive pregnant women and since K5 is closer to the actual intra-arterial pressure and more reliably detected, universal adoption of K5 to record diastolic blood pressure in hypertensive pregnancy should be considered.

Lower extremity vascular reconstruction and endovascular surgery without preoperative angiography

Background: Recent studies have shown the feasibility of performing lower extremity revascularization based on noninvasive vascular studies alone. Methods: We undertook a prospective study of patients with lower extremity ischemia who underwent revascularization without preoperative angiography. Preoperative evaluation was done with noninvasive studies including segmental pressures, ankle arm index, duplex scan, and selective use of magnetic resonance angiography. Intraoperative angiography and intra-arterial pressure measurements were used prior to revascularization. Standard patency analysis and follow-up examination were performed. Results: In all, 47 patients underwent 65 procedures (27 iliac, 38 infrainguinal) over a 3-year period. Intraoperative angiography and operative findings correlated with the noninvasive studies. There was one immediate failure, and life table analysis demonstrated primary patency rates of 92% for iliac reconstruction (29 months) and 82% for infrainguinal reconstruction (40 months). Conclusion: Preoperative evaluation for lower extremity revascularization utilizing only noninvasive vascular testing gives satisfactory results and is a safe and potentially durable alternative to routine preoperative angiography in most cases.