Cardiac oxygen supply is compromised during the night in hypertensive patients

The enhanced heart rate and blood pressure soon after awaking increases cardiac oxygen demand, and has been associated with the high incidence of acute myocardial infarction in the morning. The behavior of cardiac oxygen supply is unknown. We hypothesized that oxygen supply decreases in the morning and to that purpose investigated cardiac oxygen demand and oxygen supply at night and after awaking. We compared hypertensive to normotensive subjects and furthermore assessed whether pressures measured non-invasively and intra-arterially give similar results. Aortic pressure was reconstructed from 24-h intra-brachial and simultaneously obtained non-invasive finger pressure in 14 hypertensives and 8 normotensives. Supply was assessed by Diastolic Time Fraction (DTF, ratio of diastolic and heart period), demand by Rate-Pressure Product (RPP, systolic pressure times heart rate, HR) and supply/demand ratio by Adia/Asys, with Adia and Asys diastolic and systolic areas under the aortic pressure curve. Hypertensives had lower supply by DTF and higher demand by RPP than normotensives during the night. DTF decreased and RPP increased in both groups after awaking. The DTF of hypertensives decreased less becoming similar to the DTF of normotensives in the morning; the RPP remained higher. Adia/Asys followed the pattern of DTF. Findings from invasively and non-invasively determined pressure were similar. The cardiac oxygen supply/demand ratio in hypertensive patients is lower than in normotensives at night. With a smaller night-day differences, the hypertensives’ risk for cardiovascular events may be more evenly spread over the 24 h. This information can be obtained noninvasively

Identifying Isolated Systolic Hypertension From Upper-Arm Cuff Blood Pressure Compared With Invasive Measurements

Isolated systolic hypertension (ISH) is the most common form of hypertension and is highly prevalent in older people. We recently showed differences between upper-arm cuff and invasive blood pressure (BP) become greater with increasing age, which could influence correct identification of ISH. This study sought to determine the difference between identification of ISH by cuff BP compared with invasive BP. Cuff BP and invasive aortic BP were measured in 1695 subjects (median 64 years, interquartile range [55-72], 68% male) from the INSPECT (Invasive Blood Pressure Consortium) database. Data were recorded during coronary angiography among 29 studies, using 21 different cuff BP devices. ISH was defined as ≥130/<80 mm Hg using cuff BP compared with invasive aortic BP as the reference. The prevalence of ISH was 24% (n=407) according to cuff BP but 38% (n=642) according to invasive aortic BP. There was fair agreement (Cohen κ, 0.36) and 72% concordance between cuff and invasive aortic BP for identifying ISH. Among the 28% of subjects (n=471) with misclassification of ISH status by cuff BP, 20% (n=96) of the difference was due to lower cuff systolic BP compared with invasive aortic systolic BP (mean, -16.4 mm Hg [95% CI, -18.7 to -14.1]), whereas 49% (n=231) was from higher cuff diastolic BP compared with invasive aortic diastolic BP (+14.2 mm Hg [95% CI, 11.5-16.9]). In conclusion, compared with invasive BP, cuff BP fails to identify ISH in a sizeable portion of older people and demonstrates the need to improve cuff BP measurements

Effects of arteriovenous fistulas on cardiac oxygen supply and demand

Effects of arteriovenous fistulas on cardiac oxygen supply and demand.BackgroundArteriovenous (AV) fistulas used for hemodialysis access may affect cardiac load by increasing the preload while decreasing the afterload. In dogs, AV fistulas have also been shown to affect coronary perfusion negatively. We investigated the net effect of AV fistulas on cardiac oxygen supply and demand.MethodsAortic pressure waves were reconstructed from finger pressure recordings obtained on the nonfistula arm using a wave-form filter. Changes in systolic, mean, and diastolic aortic pressure were calculated, together with changes in heart rate (HR), stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR) during a 60-second compression of AV fistulas in 10 patients. Changes in cardiac supply and demand were estimated by calculating the area under the aortic pressure curve during diastole [diastolic pressure time index (DPTI)] and systole [systolic pressure time index (SPTI)], respectively.ResultsDuring fistula compression, systolic, mean and diastolic pressure increased by 4.2 ± 4.3, 2.6 ± 3.0, and 2.8 ± 2.9mm Hg (mean ± sd, all P < 0.05). The HR decreased by 3.8 ± 2.5 beats per minute (P < 0.01), and SV decreased 3.7 ± 6.1% (NS). CO decreased 9.4 ± 8.6%, and SVR increased 14.3 ± 11.7% (both P < 0.05). The SPTI increased by 1.5 ± 1.5mm Hg · sec (P < 0.01), and the DPTI increased by 7.6 ± 8.1mm Hg · sec (14.8% increase, P < 0.05) during compression. The ratio of supply and demand (DPTI/SPTI) improved by 13.5 ± 13.0% (P < 0.01) when the fistula was compressed.ConclusionAV fistulas have a small effect on left ventricular oxygen demand, but decrease cardiac oxygen supply considerably

Reconstruction of brachial artery pressure from noninvasive finger pressure measurements

Background Pulse wave distortions, mainly caused by reflections, and pressure gradients, caused by flow in the resistive vascular tree, may cause differences between finger and brachial artery pressures. These differences may limit the use of finger pressure measurements. We investigated whether brachial artery pressure waves could be reconstructed from finger pressure measurements by correcting for the pressure gradient in addition to correction for pulse wave distortion with a previously described filter. Methods and Results Finger artery pressure (with Finapres), intra-arterial brachial artery pressure (BAP), Riva-Rocci/Korotkoff (RRK), oscillometric, and return-to-flow (RTF) measurements were simultaneously performed in 57 healthy elderly subjects and patients with vascular disease and/or hypertension. A generalized waveform filter was used to correct for pulse wave distortions. Correction equations for the pressure gradient, based on finger pressure, RRK, RTF, or oscillometric measurements, were obtained in 28 randomly selected subjects and tested in 29. Before reconstruction, Finapres underestimated mean and diastolic BAP (finger pressure minus BAP: systolic, -3.2±16.9 mm Hg; mean, -13.0±10.5 mm Hg; diastolic, -8.4±9.0 mm Hg [mean±SD]). After filtering, reconstructed BAP waves were similar to actual BAP in shape but not in pressure level. Optimal correction for the pressure gradient with an equation based on RTF measurements reduced the pressure differences to meet American Association for the Advancement of Medical Instrumentation criteria (reconstructed finger pressure minus BAP: systolic, 3.7±7.0 mm Hg; mean, 0.7±4.6 mm Hg; and diastolic, 1.0±4.9 mm Hg). Conclusions BAP waves can be reconstructed from noninvasive finger pressure registrations when finger pressure waves are corrected for pulse wave distortion and individual pressure gradients

Vitamin K antagonist use and renal function in pre-dialysis patients

Pauline WM Voskamp,1 Friedo W Dekker,1 Maarten B Rookmaaker,2 Marianne C Verhaar,2 Willem Jan W Bos,3 Merel van Diepen,1 Gurbey Ocak2 1Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, the Netherlands; 2Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, the Netherlands; 3Department of Nephrology, Sint Antonius Hospital, Nieuwegein, the Netherlands Purpose: A post hoc analysis of a recent trial on direct oral anticoagulants versus vitamin&nbsp;K antagonists showed that amongst patients with mildly decreased kidney function, use of vitamin K antagonists was associated with a greater decline in renal function than use of direct oral anticoagulants. Whether these vitamin K antagonist effects are the same in pre-dialysis patients is unknown. Therefore, the aim of this study was to investigate the association between vitamin K antagonist use and the rate of renal function decline and time until start of dialysis in incident pre-dialysis patients.Methods: Data from 984 patients from the PREdialysis PAtient REcord study, a multicenter follow-up study of patients with chronic kidney disease who started pre-dialysis care in the Netherlands (1999&ndash;2011), were analyzed. Of these patients, 101 used a vitamin K antagonist. Linear mixed models were used to compare renal function decline between vitamin K antagonist users and non-users. Cox proportional hazards models were used to estimate the HR with 95% CI for starting dialysis.Results: Vitamin K antagonist use was associated with an extra change in renal function of &ndash;0.09 (95% CI &ndash;1.32 to 1.13) mL/min/1.73 m2 per year after adjustment for confounding. The adjusted HR for the start of dialysis was 1.20 (95% CI 0.85 to 1.69) in vitamin K antagonist users, compared to non-users. Conclusion: In incident pre-dialysis patients, the use of vitamin K antagonists was not associated with an accelerated kidney function decline or an earlier start of dialysis compared to non-use. The lack of knowledge on the indication for vitamin K antagonist use could lead to confounding by indication. Keywords: coumarins, epidemiology, chronic kidney disease, glomerular filtration rat

Aortic stiffness and the balance between cardiac oxygen supply and demand: the Rotterdam Study

Objectives Aortic stiffness is an independent predictor of cardiovascular morbidity and mortality. We investigated whether aortic stiffness, estimated as aortic pulse wave velocity, is associated with decreased perfusion pressure estimated as the cardiac oxygen supply potential. Methods Aortic stiffness and aortic pressure waves, reconstructed from finger blood pressure waves, were obtained in 2490 older adults within the framework of the Rotterdam Study, a large population-based study. Cardiac oxygen supply and demand were estimated using pulse wave analysis techniques, and related to aortic stiffness by linear regression analyses after adjustment for age, sex, mean arterial pressure and heart rate. Results Cardiac oxygen demand, estimated as the Systolic Pressure Time Index and the Rate Pressure Product, increased with increasing aortic stiffness [0.27 mmHg s (95% confidence interval: 0.21; 0.34)] and [42.2 mmHg/min (95% confidence interval: 34.1; 50.3)], respectively. Cardiac oxygen supply potential estimated as the Diastolic Pressure Time Index decreased [-0.70 mmHg s (95% confidence interval: -0.86; -0.54)] with aortic stiffening. Accordingly, the supply/demand ratio Diastolic Pressure Time Index/ Systolic Pressure Time Index -1.11 (95% confidence interval: -0.14; -0.009) decreased with increasing aortic stiffness. Conclusion Aortic stiffness is associated with estimates of increased cardiac oxygen demand and a decreased cardiac oxygen supply potential. These results may offer additional explanation for the relation between aortic stiffness and cardiovascular morbidity and mortality