Hemodynamic consequences of Cimino fistulas studied with finger pressure measurements during fistula compression

Comparison of effects of peripheral vasculature on tonometric radial pulse and cuff-based brachial pulse waveform as used in estimation of central aortic pressures

OBJECTIVE

Aortic pressure estimation requires reliable peripheral pulse waveform acquisition. The peripheral waveform can change with local vascular effects that can be independent of aortic pressure. This study quantifies the effects of peripheral vasculature changes on radial and brachial waveforms.

DESIGN AND METHOD

In 20 subjects (37± 15 years, 7 female), brachial volumetric displacement (cuff-based) and radial tonometry waveforms were simultaneously measured whilst a cuff around the hand on the same arm was inflated to induce transmural pressures of -60, -30, -15, 0, 15 and 30 mmHg, altering local peripheral resistance and compliance by graded arterial wall unloading. Aortic blood pressure (BP), augmentation index (AIx) and ejection duration were calculated from the measurements using a generalized transfer function. The parameters under unloaded conditions were compared to baseline measurements.

RESULTS

Brachial systolic and diastolic BP did not change throughout the experiment. Altering peripheral resistance and compliance did not significantly change calculated aortic BP values, although changes were nominally greater for radial (maximum +8±1 mmHg) compared to brachial (maximum +2±1 mmHg) waveforms. AIx at 0 mmHg transmural pressure (maximum arterial wall unloading) was higher when derived from radial waveforms (+24±3%, p<0.001) but not when derived from brachial waveforms.

CONCLUSIONS

Localized changes in peripheral resistance and compliance affect tonometer acquired radial waveforms but not volumetric displacement acquired brachial pressure waveforms, as judged by computed central aortic augmentation pressure parameters. This suggests aortic pressure estimation from the brachial cuff waveform is less sensitive to peripheral vasculature disturbances that alter the peripheral arterial pulse morphology.

ASDIN white paper: Assessment and management of hemodialysis access-induced distal ischemia by interventional nephrologists

Although not common, hemodialysis access-induced distal ischemia is a serious condition resulting in significant hemodialysis patient morbidity. Patients with signs and symptoms suggestive of hand ischemia frequently present to the general and interventional nephrologist for evaluation. In order to care for these cases, it is necessary to understand this syndrome and its management. Most cases can be managed conservatively without intervention. Some cases requiring intervention may be treated using techniques within the scope of practice of the interventional nephrologists while other cases require vascular surgery. In order for the interventional nephrologists to evaluate and manage these cases in a timely and appropriate manner, practice guidelines are presented.

A successful case of percutaneous fistula closure in a patient with high output heart failure and extracardiac arteriovenous fistula

Intra-cardiac shunt diseases may cause chronic ventricular volume overload, but extra-cardiac fistula could also cause high-output heart failure (HF). A patient presented with high-output HF and significant extra-cardiac shunt flow. Although the size and shape of the patient's left ventricle suggested dilated cardiomyopathy, considerable origins were not identified except for a high-flow fistula between the right subclavian artery and right internal jugular vein. Right heart catheter examination revealed inappropriately high cardiac output. Left-to-right shunt ratio was calculated at 40.3% from an oximetry run, under the assumption that the left anonymous vein which was not contaminated with any shunt flow could be substituted for venous return from the upper body. We could determine the indication of fistula closure according to the estimated high left-to-right shunt ratio, reducing cardiac output by 42.7% which was similar to the pre-estimated left-to-right shunt ratio. Two months later, the patient's serum B-type natriuretic peptide level and left ventricular end-diastolic and end-systolic diameters were decreased. The proposed method to estimate the left-to-right shunt ratio was useful in determining the indication for fistula closure in a patient with HF and a significant shunt fistula. <Learning objective: A significant extracardiac left-to-right shunt more than 30-35% could cause heart failure with left ventricular dilatation similar to dilated cardiomyopathy. One can decide fistula closure with the finding of left-to-right shunt ratio calculated using a transcatheter oximetry run. It is mandatory that the venous oxygen saturation at the upper stream of fistula is determined precisely without the contamination of arterial blood. In this case, the oxygen saturation at the left anonymous vein substituted for it.>.

Effect of high flow arteriovenous fistula on cardiac function in hemodialysis patients

BACKGROUND

Vascular access for hemodialysis (HD) with an inappropriately high flow may underlie the onset of high output heart failure (HOHF).The aim of this study was to determine the prevalence of high flow access (HFA) in chronic HD patients, and to determine its effects on cardiac functions.

METHODS

This cross sectional study was conducted on 100 chronic hemodialysis patients through arteriovenous fistula (AVF). The study cohort was subdivided into 2 groups based on AVF flow: Group A (Non-HFA group with Qa < 2000 ml/min), and Group B (HFA group with Qa ≥ 2000 ml/min). AVF flow (Qa) was assessed using Color Doppler ultrasonography. Transthoracic echocardiography was performed for all patients to assess cardiac dimensions and functions.

RESULTS

Prevalence of HFA among study population was 24%. Mean AVF Qa was 958.63 ± 487.35 and 3430.13 ± 1256.28 ml/min, for group A and B respectively. The HFA group demonstrated a significant dilatation in LV dimensions and volumes and significantly larger LA volume as compared to non-HFA group. A significantly lower LV ejection fraction [EF] was also observed in group B with a mean value of 57.32 ± 6.19% versus 62.90 ± 5.76%. A significant association between HFA group and high Qa/cardiac output (CO) ratio (≥20%) was also observed.

CONCLUSION

HFA is a prevalent hemodialysis vascular access problem. HFA was associated with dilated LV dimensions, impaired LV systolic function. High Qa/CO ratio (≥20%) was an independent predictor of high output heart failure (HOHF) in our study population.

Influence of autologous arteriovenous fistula on the blood supply to the hand in very elderly hemodialyzed patients

INTRODUCTION

Arteriovenous fistula (AVF) creation for hemodialysis (HD) could predispose to local arterial insufficiency of the hand (steal syndrome). Patients with diabetes mellitus, peripheral arterial disease and elderly patients tend to have a higher risk of hand ischemia.

PURPOSE AND METHODS

To estimate the influence of AVF on the blood supply to the hands in the elderly population and to identify steal syndrome cases by non-invasive diagnostics (finger photoplethysmography (PPG), pulse volume recording (PVR), Doppler analysis and pulseoxymetry). The evaluation was carried out in 25 random patients (10 females, 15 males) >75 yrs of age (79.6 +/- 3.87 yrs), whose functioning autologous AVFs had been placed at least 1 month previously.

RESULTS

Mean PPG and PVR amplitudes did not differ in statistical analysis (p > 0.05) between hands with and without an AVF. One patient (4%) with end-to-side anastomosis was diagnosed with steal syndrome (typical manifestation confirmed in PPG, Doppler and pulseoxymetry). Two other patients with high brachio-cephalic anastomosis presented subclinical steal syndrome (only low PPG and PVR).

CONCLUSIONS

Even in the very elderly, AVF creation should be considered due to a lesser influence on the blood supply to the hands. Non-invasive diagnostics used by us seemed to be useful in identifying steal syndrome after AVF creation.

Hemodynamic cardiovascular risk factors in chronic kidney disease: what are the effects of intervention?

Left ventricular (LV) volume and pressure overload occur frequently in chronic kidney disease (CKD). Anemia is a risk factor for left ventricular hypertrophy (LVH) and dilatation, heart failure, and death. Normalization of hemoglobin with erythropoietin may prevent LVH and dilatation in CKD, but in patients in later phases of their cardiac disease, this intervention is not of benefit. Increased vascular volume causes hypertension, which in turn causes LVH, cardiac failure, and ischemic heart disease (IHD). Manifestations of arteriosclerosis are associated with adverse cardiac outcomes, and angiotensin converting enzyme (ACE) inhibitors may improve LVH and markers of arteriosclerosis. Aortic stenosis in dialysis patients occurs infrequently, but may deteriorate rapidly. The hemodialysis milieu is the quintessential model of LV overload cardiomyopathy.

Effects of the creation of arteriovenous fistula for hemodialysis on cardiac function and natriuretic peptide levels in CRF

BACKGROUND

Cardiac failure occasionally is caused by the creation of vascular access for hemodialysis. However, the influence of an arteriovenous (AV) fistula on cardiac function has not been fully elucidated. The present study investigated serial changes in cardiac function and hormonal levels after the AV fistula operation.

METHODS

Sixteen patients with chronic renal failure underwent echocardiographic studies before and 3, 7, and 14 days after the AV fistula operation. Plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations were measured before and 1, 3, 6, 10, and 14 days after the operation.

RESULTS

Creation of an AV fistula produced significant elevations in left ventricular (LV) end-diastolic diameter (+4%), fractional shortening (+8%), and cardiac output (CO; +15%). In LV inflow velocities measured by Doppler echocardiography, deceleration time of the early diastolic filling wave shortened (-12%) and the ratio of the peak velocity of early diastolic to atrial filling (E-A ratio) increased (+18%). The difference in duration of LV inflow and pulmonary venous flow at atrial contraction, a marker of LV end-diastolic pressure, significantly shortened day 14 after the operation (-37%). That is, creation of an AV fistula induced LV diastolic dysfunction toward a restrictive filling pattern. Both ANP and BNP levels increased after the operation, and maximal percentages of increase were observed after 10 days (ANP, +48%; BNP, +68%). In the relationship between cardiac function and hormonal response, the increase in CO was associated with elevation of ANP levels (r = 0.61; P = 0.01), but not BNP levels. Conversely, the increase in E-A ratio correlated only with BNP level elevation (r = 0.60; P = 0.01).

CONCLUSION

Our observations indicate that creation of an AV fistula has significant effects on cardiac systolic and diastolic performance, and ANP release is induced by volume loading, but BNP release is stimulated by LV diastolic dysfunction.

Effects of arteriovenous fistulas on cardiac oxygen supply and demand

BACKGROUND

Arteriovenous (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.

METHODS

Aortic 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.

RESULTS

During fistula compression, systolic, mean and diastolic pressure increased by 4.2 +/- 4.3, 2.6 +/- 3.0, and 2.8 +/- 2.9 mm 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 +/- 1.5 mm Hg.sec (P < 0.01), and the DPTI increased by 7.6 +/- 8.1 mm 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.

CONCLUSION

AV fistulas have a small effect on left ventricular oxygen demand, but decrease cardiac oxygen supply considerably.