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Biomedical subjects

T G Pickering

Publications and source records attributed to T G Pickering.

At least 217 records · Page 12Linked to original sources
PubMed1985

Indication for intervention in patients with renovascular hypertension.

It is now possible to accurately identify patients with renovascular hypertension who need renal angioplasty or revascularization. Evaluation does not require hospitalization and begins with the determination of an ambulatory plasma renin activity (PRA) indexed against sodium excretion and a captopril test. Subsequently differential renal vein renins with matching inferior vena caval (IVC) renins are measured often with converting enzyme inhibition. Identifying criteria are as follows: (1) high PRA indexed against sodium excretion, (2) hypersecretion of renin following captopril administration, (3) absence of renin secretion from the contralateral kidney, and (4) an ipsilateral renal vein renin increment at least 50% greater than the matching IVC renin. Patients who meet the criteria are admitted for percutaneous transluminal renal angioplasty.

Angiography↗
PubMed1985

Comparison of renal vein renin activity in hypertensive patients with stenosis of one or both renal arteries.

Renal vein renin measurements were compared in 64 hypertensive patients with arteriographically documented stenoses or complete occlusion of one or both renal arteries. The characteristic pattern of curable renovascular hypertension, i.e. increased increment of renin from the ischaemic kidney with contralateral suppression of renin secretion, was seen not only in patients with unilateral stenoses, but also in most patients with bilateral stenoses. Contralateral suppression was less marked in azotemic patients. The highest increments of renal vein renin were seen when the renal artery was completely occluded. The patterns were similar following acute or chronic administration of captopril, suggesting that angiotensin II is not responsible. Increased sodium delivery to the macula densa is postulated as a possible cause of contralateral suppression.

Angiotensin II↗
PubMed1984

Whole blood viscosity as a determinant of cardiac hypertrophy in systemic hypertension.

The relationships among blood pressure (BP), blood viscosity and echocardiographic left ventricular (LV) muscle mass were evaluated in 24 patients with essential hypertension and in 13 normotensive control subjects. LV mass was greater in the hypertensive patients than in the control subjects (225 +/- 69 vs 170 +/- 31 g, p less than 0.02) as was blood viscosity at a shear rate of 104 sec-1 (4.7 +/- 0.1 vs 4.3 +/- 0.2 cp, p less than 0.005). Among the hypertensive patients, LV mass was most closely related to viscosity at 104 sec-1 (r = 0.80, p less than 0.001), whereas only weak correlations were found between LV mass and systolic or diastolic BP (r = 0.45, p less than 0.05 for both). The 14 hypertensive patients with normal LV mass had viscosity similar to that in control subjects (4.5 +/- 0.3 vs 4.3 +/- 0.2 cp), whereas viscosity was consistently increased (5.0 +/- 0.4 cp, p less than 0.02) in hypertensive patients with LV hypertrophy. Thus, increased blood viscosity may be a determinant of or a response to hypertensive cardiac hypertrophy.

Adult↗
PubMed1984

Role of balloon dilatation in the treatment of renovascular hypertension.

Renal angioplasty is now well established as a treatment for renovascular hypertension. In patients with fibromuscular dysplasia, the technique is usually technically successful, and the therapeutic effect on blood pressure is as good as with surgical revascularization. In patients with atheroma, the success rate is lower, mainly because of technical problems associated with inability to pass the catheter across the stenosis. In patients in whom this can be done, the results are similar to those of surgery. In our experience, the rate of restenosis is acceptably low, and in most patients, improvement has been maintained over two years. Selection of suitable patients is based on screening from the clinical history and examination, combined with renin-sodium profiling. Renal vein renin measurements have been found reliably to predict the therapeutic outcome of angioplasty, and the incremental method of Vaughan has been preferable to use of the ratio between the two renal veins. In patients with high renin-sodium profiles or in those with normal profiles and a clinical suspicion of renovascular hypertension, renal vein renin values would be determined next, usually with digital intravenous angioplasty. A single test dose of captopril may also be useful as a screening test. If these procedures do indicate the presence of renovascular hypertension, the patient is admitted to the hospital, and arteriography and angioplasty are performed at the same session.

Angioplasty, Balloon↗
PubMed1984

Predictive value and changes of renin secretion in hypertensive patients with unilateral renovascular disease undergoing successful renal angioplasty.

Peripheral and renal vein renin activity was measured in 46 hypertensive patients with arteriographically diagnosed unilateral renal artery stenosis before and six months after technically successful renal angioplasty. The renin-sodium profile was high in 80 percent before angioplasty, fell in all patients, and became normal or low in 85 percent after angioplasty. Renal vein renin activity, which initially showed lateralization of renin secretion to the ischemic kidney with contralateral suppression, became normal. Renal vein renin activity was more reliable for predicting the therapeutic response when expressed as the increment of renin for each renal vein over the infrarenal vena caval value (sensitivity 74 percent, specificity 100 percent) than as the ratio between the two renal veins (sensitivity 62 percent, specificity 60 percent). The predictive value of renal vein renin activity is poor when plasma renin activity is stimulated by long-term administration of captopril. These data support the usefulness and define the limitations of peripheral and renal vein renin measurements in selecting patients for treatment by renal angioplasty.

Adult↗
PubMed1984

Clinical evaluation of renovascular hypertension and therapeutic decisions.

The renal arteriogram alone, useful as an anatomic guide for the surgeon or radiologist, is inadequate to predict potential blood pressure reversal by correction of the obstructing lesion. A patient must be identified as having functionally significant renal arterial disease before intervention can be recommended. The authors discuss uncovering functionally significant renal artery stenosis, the pathophysiology of experimental Goldblatt hypertension, and criteria to identify renovascular hypertension, including peripheral plasma renin activity and differential renal-vein renin determinations.

Adult↗
PubMed1984

The current role of renal angioplasty in the treatment of renovascular hypertension.

Percutaneous transluminal renal angioplasty, a relatively noninvasive technique, has assumed an increasing role in the treatment of renovascular hypertension. The combined advent of digital subtraction angiography, renal-vein renin samples, and percutaneous transluminal angioplasty have prompted many physicians to reassess their treatment strategies. The authors present their experience with renal angioplasty at the New York Hospital and briefly describe the history and mechanism of action of this procedure.

Adult↗
PubMed1983

Cigarette smoking and renovascular hypertension.

A retrospective cohort study to investigate the association between smoking and renal artery stenosis compared 71 patients with documented renovascular hypertension and 308 age-matched control patients with essential hypertension. 94% (30/32) of men and 74% (29/39) of women with renal artery stenosis had smoked cigarettes compared with only 43% (64/150) of men and 41% (65/158) of women in the control group. This striking relation was true for both patients with fibromuscular disease (71% smokers; 15/21) and patients with atherosclerotic lesions (88% smokers; 44/50). All renal artery stenosis groups had significantly higher systolic and diastolic blood pressures than the relevant control group. When the groups were stratified according to blood pressure, there were significantly more smokers in the renal artery stenosis group at every level of blood pressure.

Diastole↗
PubMed1983

Percutaneous transluminal renal angioplasty in renovascular hypertension due to atheroma or fibromuscular dysplasia.

We attempted percutaneous transluminal renal angioplasty in 89 patients with hypertension and renal-artery stenosis (including 51 with atheromatous and 31 with fibromuscular stenoses) who were then followed for an average of 16 months (range, 4 to 40). Angioplasty was technically successful in 87 per cent of the fibromuscular stenoses and in 57 per cent of the unilateral atheromatous stenoses but in only 10 per cent of the bilateral atheromatous stenoses. After successful angioplasty, blood pressure was reduced to normal or improved in 93 per cent of the patients with fibromuscular dysplasia and in 84 per cent of the patients with atheromatous disease. Angiographic follow-up at an average of 21.8 months in 15 patients showed persistent relief of the stenoses and a 12 per cent average increase in kidney size. Renal angioplasty is effective for long-term control of hypertension in patients with renal-artery stenosis due to fibromuscular dysplasia or unilateral non-ostial atheroma.

Adult↗
PubMed1983

Foil electret transducer for blood pressure monitoring.

A foil electret microphone for use under the cuff of an automatic blood pressure monitoring system is described. The transducer is designed to operate with relatively flat sensitivity over a static pressure range of 40 to 250 mm Hg (5.33 X 10(4) to 3.33 X 10(5) dyn/cm2). The new electret microphone differs from conventional microphones used for airborne sound reception in two ways: (1) the diaphragm thickness is 50 micron rather than the typical 12.5 or 25 micron, and (2) the backplate contains a set of annular ridges spaced at 4 mm rather than the typical 7-10 mm. This microphone offers three advantages over the piezoelectric microphone now in use: (1) greater tolerance in positioning the microphone over the brachial artery, (2) nearly 20-dB higher sensitivity and signal-to-noise ratio, and (3) the ability to obtain measurements with the microphone placed midway between the elbow and shoulder. Tests of the new foil electret microphone in conjunction with the automatic blood pressure monitoring system indicate that the automatic and conventional measurements of systolic and diastolic blood pressure agree to within 5 mm Hg at least 90% of the time. In addition, the electret microphone is able to obtain automatic measurements on subjects with a wider range of ages and sizes.

Acoustics↗
PubMed1983

Pheochromocytoma and prazosin.

Prazosin was used to control the signs and symptoms of excessive alpha-adrenergic activity in four patients with pheochromocytomas. Long-term dosage requirements were predicted by the blood pressure response to a single 1-mg oral dose. However, surgical management of the pheochromocytomas was inadequate with prazosin alone, and intravenous phentolamine was required to suppress the pressor surges generated by the tumor during surgical manipulation and excision.

Adult↗
PubMed1982

Comparison of antihypertensive and hormonal effects of captopril and propranolol at rest and during exercise.

Captopril and propranolol were given alone and in combination to 13 hypertensive men and the effects studied at rest (seated, supine and standing) and during exercise. The two drugs were equipotent at rest, and individual patients showed similar blood pressure responses to the two drugs. Both produced slight reduction of urinary aldosterone; when given in combination, both blood pressure and aldosterone were further reduced. During exercise the increase in blood pressure was unaffected by captopril but reduced by propranolol, and there was no correlation between individual responses to the two drugs. It is concluded that the similar effects of the two drugs on resting blood pressure are consistent with their effects on the renin-angiotensin system.

Aldosterone↗
PubMed1982

Blood pressure during normal daily activities, sleep, and exercise. Comparison of values in normal and hypertensive subjects.

Blood pressure (BP) readings were taken every 15 minutes using a noninvasive ambulatory BP recorder during 24 hours in 25 subjects with normal BP, 25 with borderline hypertension, and 25 with established essential hypertension. Readings were analyzed for four situations: (1) physician's office, (2) work, (3) at home, and (4) asleep. Treadmill exercise tests were also performed on a separate occasion with the Bruce protocol. The 24-hour recording in all three groups showed the highest BPs at work and the lowest during sleep. The situational BP changes were generally similar, but both hypertensive groups differed from normal subjects in that they showed consistently higher BPs in the physician's office than at home, whereas normal subjects showed a similar rise of systolic pressure to that of normal subjects. Pressures recorded in the physician's office gave good predictions of the average 24-hour pressure in normal and established hypertensive subjects, but not in the borderline group; in such patients, 24-hour monitoring may be of particular value in establishing the need for treatment.

Adult↗