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PubMed2000

The quincunx of surgery.

From the earliest days of surgery the central and unifying theme of the discipline has been the mastery of technical proficiency with the view to not only management of the diseased or damaged part but the preservation of general health and well being. This central tenet of the discipline has been supported by four critical columns of knowledge, each of which has amplified over the passage of time. Initially anatomy was the cornerstone of surgical intervention and mastery of surgery to a large part depended upon a secure grasp of the intricacies and relationships of corporeal macro structure. The second column comprised functional anatomy or physiology and the appreciation of organ activity enabled the subsequent delineation of malfunction during disease. Regardless of the level of sophistication that could be brought to bear upon the disease a requisite for most successful technical intervention was the management of pain and the prevention of sepsis. As the quincunx of surgery embraces a new century it must continue to evolve to maintain the balance of growth in the four supporting columns. Thus anatomy has been expanded into subcellular structure and the elucidation of function has amplified into the role of individual organelles. Similarly pathology has moved beyond the organ and cell into the genome and deletion may be conceived of in terms of codons and sequences rather than colons and spleens. Indeed it is feasible that antisense strategies may become more sensible than antibiotics. Manual and digital techniques will be supplanted by robotic intervention and visualization will move beyond the visible into the non-visible world of spectroscopy. Millimetric dexterity will need to become nanometric and the mantra must become molecular and intervention directed not only at adults or neonates but the fetus. In order to achieve such goals teaching and training strategies need dramatic revision to produce individuals capable of transforming from tactile to telemetric skills and from gentle technique to genomic intervention.

Adult↗
PubMed2000

A whole-body registration-free navigation system for image-guided surgery and interventional radiology.

RATIONALE AND OBJECTIVES: To develop and test an image-guided navigation system in which the base of reference is taken from the imaging modality, here, a helical CT scanner. METHODS: An optical digitizer together with a calibration device is used to measure the transformation matrix between the digitizer reference system and a CT reference system. During intervention, it tracks radiological and surgical tools with tool references. A specific software visually integrates the current tool position with the corresponding image information. In vitro accuracy tests were performed. RESULTS: With helical CT, freehand positioning accuracy was 1.9 +/- 1.1 mm (mean +/- SD) in vitro (n = 718). CONCLUSIONS: The navigation system developed by the authors appears to be feasible for radiological interventions as well as for minimally invasive surgery. It is not limited to a certain procedure, can be used in every region of the body, and is functional after imaging. Intraprocedural scans can be integrated immediately.

Equipment Design↗
PubMed2002

Gadodiamide as an alternative contrast agent during angioplasty in patients with contraindications to iodinated media.

PURPOSE: To evaluate gadodiamide as an alternative contrast agent for peripheral and renal angioplasty in patients with contraindications to iodinated contrast media. METHODS: Seventeen patients (10 men; mean age 74 years, range 68-83) with contraindication to iodinated contrast media were given gadodiamide as the contrast agent during peripheral and renal intra-arterial digital subtraction angiography (DSA) and subsequent percutaneous interventions (balloon angioplasty, stent placement). RESULTS: The mean volume of gadodiamide used was 136 +/- 46 mL (range 60-200). No serious side effects were observed, especially no change in renal or thyroid function; no exanthema or other allergic reactions were noted. In patients without renal artery intervention, serum creatinine at discharge remained unchanged (2.57 +/- 1.43 mg/dL to 2.40 +/- 1.28 mg/dL, p=NS). In patients undergoing angioplasty/stenting of renal artery stenoses, serum creatinine decreased significantly from 3.53 +/- 1.75 mg/dL to 2.36 +/- 1.15 mg/dL (p<0.01). All but 1 intervention was successful. Using a simple scoring system, 2 judges blinded to the contrast agent graded the quality of the peripheral DSAs as "good," whereas renal DSA images were only "sufficient." CONCLUSIONS: For patients with contraindications to iodinated materials, gadodiamide may be a suitable alternative for renal or peripheral DSA followed by angioplasty.

Aged↗
PubMed2000

Software development for registration of digital subtraction angiography (DSA) images in uterine fibroid embolization.

The ISIS Center at Georgetown University Medical Center has developed a comprehensive program for image-guided procedures in the spine. As part of this program, ISIS has developed a software application known as I-SPINE (ISIS's Spine Procedure Imaging Navigation Engine). I-SPINE is a Windows NT application, which is based on the Analyze/AVM libraries. The software architecture follows the Microsoft Foundation Classes (MFC) single document, multiple view paradigm. This has allowed the developers to add new visualization modules to I-SPINE that aid physicians in procedures outside the spine. One such procedure I-SPINE has been expanded for is uterine fibroid embolization. The idea is that by registering and subtracting post-embolization angiographic images from pre-treatment images the resulting image can be used to quantify the embolization effect on the fibroid circulation and predict the treatment response. The I-SPINE digital subtraction angiography (DSA) module allows the interventional radiologist to open a series of pre and post-embolization DSA images that shows the vascular structures of the uterus and the fibroid or fibroids. From these images, the radiologist selects an appropriate image from each series. The selected images are then hand registered using pixel shifting. Once the images are registered, the pixels are subtracted resulting in an image that shows the embolized arteries that were supplying the fibroids.

Angiography, Digital Subtraction↗
PubMed1994

Digital angiotomosynthesis for preoperative evaluation of cerebral arteriovenous malformations and giant aneurysms.

PURPOSE: To evaluate the clinical utility of the digital angiotomosynthesis technique for giving additional information regarding critical anatomy of cerebrovascular lesions before surgical intervention. METHOD: Seven arteriovenous malformations and three giant aneurysms were examined with digital angiotomosynthesis; these images were compared with conventional angiograms. RESULTS: 1) Detailed recognition of three-dimensional vascular structures of the arteriovenous malformation and giant aneurysm was facilitated by the cine mode of digital angiograms and angiotomograms. 2) Reconstructed angiotomograms could show clear separation of overlapping vessels and demonstrate fine vasculature. 3) Fine feeders, which were difficult to trace on the conventional angiogram, were more easily recognized in all cases of arteriovenous malformation. 4) Small arteries passing in close proximity to the arteriovenous malformation nidus were identifiable. 5) Fine arterial branches, being obscured by big shadows of giant aneurysms on the conventional angiograms, were well identified. 6) The anatomic relationship of bone structures to the giant aneurysm was clearly shown. CONCLUSIONS: Digital angiotomosynthesis is helpful for recognizing the three-dimensional and detailed vascular anatomy of arteriovenous malformations and giant aneurysms and provides neurosurgeons with useful information for preoperative evaluation.

Adolescent↗
PubMed1988

The effect of balloon dilatation on post-stenotic myocardial perfusion before and after stimulation of coronary flow reserve: evaluation by the densitometric parameter 'mean rise time'.

From densitometric evaluation of digital subtraction cineangiocardiograms the parameter 'Mean Rise Time' (MRT), defined as the time from the onset of local myocardial contrast medium opacification to the point of maximal opacification can be derived; this parameter revealed a close correlation with the results on myocardial perfusion obtained by Thallium-201 scintigraphy. A prolonged 'Mean Rise Time' was indicative of an impairment of myocardial perfusion. We have developed a heart-phase gated real-time digitization procedure and computer-supported method for the densitometric estimation of the MRT to obtain information about the effect of coronary balloon dilatation on myocardial perfusion before and after stimulation of coronary flow reserve by Moxaverin. In 22 patients with single vessel coronary artery disease Moxaverin caused a significant prolongation of the post-stenotic MRT (2.3 +/- 1.2s (mean +/- s.d.) vs. 2.9 +/- 1.1s, p less than 0.05), while after successful dilatation of the obstructive lesion a significant shortening of the MRT was found after stimulation of the coronary flow reserve (2.5 +/- 1.2s vs. 1.9 +/- 0.9s, p less than 0.05). A highly significant decrease in MRT after Moxaverin was measured post-dilatation in comparison to the initial pre-dilatation results (2.9 +/- 1.1s vs. 1.9 +/- 0.9s, p less than 0.005); this shows that the effect of successful balloon dilatation on the post-stenotic myocardial perfusion can be described very well by this parameter. These results demonstrate that information about post-stenotic myocardial perfusion during interventional heart catheterization can be obtained from digital densitometry.

Adult↗
PubMed1989

The clinical value of percutaneous transluminal angioscopy. Angioscopical findings in primary vascular diagnosis and in interventional radiology.

Since the introduction of ultrathin angioendoscopes into clinical application conventional or digital angiography have been controlled by using the same approach like in angiography. In dogs and angiography patients this new angioscopic method for arteries without surgical intervention has been developed. The approach is transfemoral. Endoscopy is combined with angiography, percutaneous transluminal angioplasty (PTA), thrombolysis, thrombus extraction and a new kind of stents and their application. An ultrathin endoscope with an outer diameter of 1.6 mm and working channel of 0.35 mm is used. Guide wires, contrast media and drugs for local thrombolysis can be applied through this channel. The endoscope is placed into the region of interest under fluoroscopic control and view is obtained by using 0.9% NaCl for decreasing blood flow. Endoscopy is documented by video or by a high-speed camera. It was possible to demonstrate the proceedings of dilatation, recanalization, local lysis, stent-application and thrombus-extraction.

Constriction, Pathologic↗
PubMed2007

Clinical utility of time-resolved imaging of contrast kinetics (TRICKS) magnetic resonance angiography for infrageniculate arterial occlusive disease.

OBJECTIVE: The diagnostic accuracy of magnetic resonance angiography (MRA) in the infrapopliteal arterial segment is not well defined. This study evaluated the clinical utility and diagnostic accuracy of time-resolved imaging of contrast kinetics (TRICKS) MRA compared with digital subtraction contrast angiography (DSA) in planning for percutaneous interventions of popliteal and infrapopliteal arterial occlusive disease. METHODS: Patients who underwent percutaneous lower extremity interventions for popliteal or tibial occlusive disease were identified for this study. Preprocedural TRICKS MRA was performed with 1.5 Tesla (GE Healthcare, Waukesha, Wis) magnetic resonance imaging scanners with a flexible peripheral vascular coil, using the TRICKS technique with gadodiamide injection. DSA was performed using standard techniques in angiography suite with a 15-inch image intensifier. DSA was considered the gold standard. The MRA and DSA were then evaluated in a blinded fashion by a radiologist and a vascular surgeon. The popliteal artery and tibioperoneal trunk were evaluated separately, and the tibial arteries were divided into proximal, mid, and distal segments. Each segment was interpreted as normal (0% to 49% stenosis), stenotic (50% to 99% stenosis), or occluded (100%). Lesion morphology was classified according to the TransAtlantic Inter-Society Consensus (TASC). We calculated concordance between the imaging studies and the sensitivity and specificity of MRA. The clinical utility of MRA was also assessed in terms of identifying arterial access site as well as predicting technical success of the percutaneous treatment. RESULTS: Comparisons were done on 150 arterial segments in 30 limbs of 27 patients. When evaluated by TASC classification, TRICKS MRA correlated with DSA in 83% of the popliteal and in 88% of the infrapopliteal segments. MRA correctly identified significant disease of the popliteal artery with a sensitivity of 94% and a specificity of 92%, and of the tibial arteries with a sensitivity of 100% and specificity of 84%. When used to evaluate for stenosis vs occlusion, MRA interpretation agreed with DSA 90% of the time. Disagreement occurred in 15 arterial segments, most commonly in distal tibioperoneal arteries. MRA misdiagnosed occlusion for stenosis in 11 of 15 segments, and stenosis for occlusion in four of 15 segments. Arterial access was accurately planned based on preprocedural MRA findings in 29 of 30 patients. MRA predicted technical success 83% of the time. Five technical failures were due to inability to cross arterial occlusions, all accurately identified by MRA. CONCLUSION: TRICKS MRA is an accurate method of evaluating patients for popliteal and infrapopliteal arterial occlusive disease and can be used for planning percutaneous interventions.

Adult↗
PubMed1995

Intraoperative digital subtraction angiography after thromboembolectomy: preliminary experience.

PURPOSE: To evaluate the potential influence of intraoperative digital subtraction angiography (DSA) on surgical strategy after balloon thromboembolectomy for acute lower limb ischemia. METHODS: Thirty-six consecutive patients with critical limb ischemia were treated with balloon catheter thromboembolectomy assessed by intraoperative digital subtraction angiography. The need for further intervention was determined by the surgeon based on the DSA information. Primary completion DSAs were made in every procedure; subsequent completion DSAs were performed after reinterventions at the discretion of the surgeon. RESULTS: Initial treatment in this patient group consisted of 14 embolectomies and 26 thrombectomies. From the completion DSAs of these 40 procedures, a reintervention was judged necessary in 27 (68%). Of these 27 reinterventions, 17 underwent a secondary DSA; evidence supporting a third intervention was found in 11 (64%). Overall, a total of 69 DSAs were performed in these patients. Mortality was 22% (8 patients); 38% (5) in embolectomy patients and 13% (3) in the thrombectomy cohort. Eighty-eight percent of the embolectomy survivors had an uneventful recovery, while only 25% of the thrombectomy survivors experienced an uncomplicated follow-up. In one quarter of the surviving thrombectomy patients, a surgical revascularization resulted in limb salvage; in 45%, a major amputation was the outcome. CONCLUSIONS: In this study, the completeness of balloon catheter thromboembolectomy was assessed by intraoperative DSA. As a result, 68% of the procedures required one or more reinterventions for residual lesions. Intraoperative DSA is a simple and quick technique that may be a promising adjunct to intraoperative balloon thromboembolectomy.

Angiography, Digital Subtraction↗
PubMed2005

Reducing the digital divide for low-income women with breast cancer: a feasibility study of a population-based intervention.

A fundamental challenge to helping underserved women and their families cope with breast cancer is providing them with easily accessible, reliable health care information and support. This is especially true for low-income families living in rural areas where resources are few and frequently distant as well as low-income families in urban areas where access to information and support can be complex and overwhelming. The Internet is one mechanism that has tremendous potential to help these families cope with breast cancer. This article describes a feasibility test of the potential for the National Cancer Institute's (NCI's) Cancer Information Service (CIS) to provide access to an Internet-based system that has been shown to improve quality of life for underserved breast cancer patients. The test was conducted in rural Wisconsin (low socioeconomic status [SES] Caucasian women) and in Detroit, Michigan (low SES African American women), and compares the effectiveness of several different dissemination strategies. Using these results we propose a model for how CIS telephone and partnership program services could efficiently disseminate such information and support systems. In doing so we believe that important steps can be taken to close the digital divide that separates low-income families from the resources they need to effectively face cancer. This is the first of two articles coming from this study. A companion article reports on an evaluation of the use and impact of this system on the women who were given access to it.

Breast Neoplasms↗
PubMed2002

Hybrid MR interventional imaging system: combined MR and angiography suites with single interactive table. Feasibility study in vascular liver tumor procedures.

Our objective was to evaluate the feasibility of a hybrid system consisting of a high-field MR and fully equipped digital subtraction angiography (DSA) unit for MR-guided vascular interventions. In a newly built hybrid system, consisting of a high-field MRI and a fully equipped DSA unit, elective interventional hybrid procedures were performed. Between May 2000 and November 2001, 30 patients with liver tumors underwent MR-guided chemoembolization using the hybrid system. During the intervention accurate catheter position was monitored with real-time and dynamic MR imaging. Elective hybrid interventional vascular procedures were performed successfully in 23 patients with liver metastases and hepatocellular carcinoma ( n=7). Patients could be transferred between the MRI and angiographic units on a carbon fiber tabletop within 10 s. Initial clinical trials demonstrated that in the chemoembolization of primary and secondary liver tumors the hybrid approach resulted in a change of catheter position in 40% of procedures. In combining high-field MR system and a fully equipped interventional vascular angiographic unit as backup, this hybrid system improves the therapeutic capabilities of interventional vascular procedures in the liver.

Angiography, Digital Subtraction↗
PubMed2000

Frequency and characteristics of enlarging common melanocytic nevi.

OBJECTIVE: To analyze the frequency and characteristics of enlarging common melanocytic nevi. DESIGN: Cohort study using digital epiluminescence microscopy (ELM) for documentation and follow-up, with a median follow-up interval of 11.4 months. SETTING: A dermatology department at a university hospital in Vienna, Austria. PATIENTS: One thousand six hundred twelve melanocytic nevi appearing clinically as common nevi, obtained from 385 patients (mean [+/-SD] age, 34.2 +/- 14.8 y; 55.6% female). INTERVENTIONS: Follow-up examination and documentation by digital ELM. MAIN OUTCOME MEASURES: Frequency of enlarging nevi according to age and comparison of ELM features observed in enlarging and nonenlarging nevi. RESULTS: Enlargement was found in 5.3% (n = 86) of nevi. The frequency of enlarging nevi was inversely related to age (P<.001), in that enlarging nevi were common in patients younger than 20 years and relatively rare in older age groups. Epiluminescence microscopy revealed a peripheral rim of brown globules in 48.8% (n = 42) of enlarging nevi. In contrast, a peripheral rim of brown globules was found in only 0.7% (n = 11) of nevi without enlargement (P<.001). Enlarging nevi that were excised in children and adolescents showed no histological signs of atypia. In older age groups, 48.1% of excised enlarging nevi that were clinically diagnosed as common nevi showed some histological signs of atypia. None of the excised enlarging lesions was histologically diagnosed as melanoma. CONCLUSIONS: The frequency of enlarging common nevi is inversely related to age. In the absence of clinical signs of atypia, enlargement alone does not indicate malignancy. A peripheral rim of brown globules is a characteristic ELM feature of symmetrically enlarging melanocytic nevi.

Adult↗
PubMed2005

Dynamic CE-MRA for endoleak classification after endovascular aneurysm repair.

AIM: To evaluate the value of dynamic contrast enhanced magnetic resonance angiography (CE-MRA) for classification of endoleaks after endovascular aneurysm repair (EVAR). MATERIALS AND METHODS: Twenty-eight patients, between 2 days and 54 months after EVAR, were evaluated with CTA, MRI and dynamic CE-MRA. The additional diagnostic value of the dynamic 3D CE-MRA was evaluated by determining the ability of the dynamic series in pinpointing the site of inflow of an endoleak. RESULTS: An endoleak was detected in 23 patients. Seventeen of the 23 dynamic series were technically successful (no disturbing artifacts limiting the diagnostic value). Using MRI our findings were: 2 type I, 6 type II, 1 type III, no type IV endoleaks and in 14 cases classification could not be made. The classification results for MRI plus the dynamic CE-MRA were: 2 type I, 12 type II, 1 type III, no type IV endoleaks and in eight cases classification could not be made. In six cases the dynamic MRA allowed classification of the endoleak, which was not possible with the non-dynamic images alone (p=0.091, Fisher exact). CONCLUSION: This pilot study shows that dynamic CE-MRA can have additional value in the classification of endoleaks. Dynamic CE-MRA might obviate the need for diagnostic digital subtraction angiography and aid planning for intervention.

Aged↗
PubMed2006

Association of a traditional vs shared meal decision-making and preparation style with eating behavior of Hispanic women in San Diego County.

OBJECTIVE: To examine the influence of meal decision-making and preparation on Hispanic women's dietary practices. DESIGN: One-on-one structured interviews were conducted, assessing meal decision-making and preparation practices, barriers, and behavioral strategies to eating low-fat and high-fiber diets, fat and fiber intake, demographic, and other psychosocial factors. SUBJECTS/SETTING: The study population included 357 Hispanic women living in the southern or central regions of San Diego County. Participants were recruited via random-digit dialing to a tailored nutrition communication intervention. MAIN OUTCOME MEASURE: Household decision-making style (alone vs with family) by household activity (decides meals, prepares meals, and decides snacks). STATISTICAL ANALYSES PERFORMED: Multiple logistic regressions were used to evaluate associations between the predictors and dependent variable. All models included adjustments for potential confounders, such as marital status, education, employment, age, and acculturation. RESULTS: A positive statistical association between Hispanic women's acculturation level and shared decision-making style was found. Also, Hispanic women in shared decision-making households faced greater psychosocial barriers to healthful eating and reported less healthful eating compared with Hispanic women in traditional households. Women in shared decision-making households were more likely to eat at fast-food restaurants, less likely to engage in behavioral strategies promoting fiber consumption, eat more saturated fat, and encounter more barriers to reduce dietary fat as compared with Hispanic women in traditional households. Acculturation did not attenuate differences in psychosocial and dietary practices between shared decision-making and traditional households. CONCLUSIONS: Study findings suggest intervention efforts should focus on different aspects of healthful eating among Hispanic women in shared-decision, compared with traditional, households.

Acculturation↗
PubMed1990

Surgical treatment of distal ulnar artery aneurysm.

In the past 7 years, we have encountered six patients with finger ischemia as a result of digital artery occlusion associated with seven distal ulnar artery aneurysms. Our experience with the management of these patients forms the basis of this report. All patients were men, with a mean age of 29 years, and all experienced repetitive trauma to the involved upper extremity. Each patient presented with the acute onset of cool and painful digits, with no previous history of cold sensitivity or Raynaud's syndrome. None of the patients had any serologic or clinical evidence of autoimmune disease. Angiography revealed occlusion of the ulnar artery on the affected side in two patients and patent ulnar artery aneurysms in the remaining five patients. There was occlusion of multiple common and proper digital arteries in all patients. One patient with bilateral ulnar artery aneurysms underwent operative repair consisting of aneurysm excision and replacement with autogenous vein grafts from the lower extremity. All patients have improved symptoms, and the grafts remained patent over a mean follow-up of 24 months (range: 13 to 57 months). Based on these results, we recommend that excision and grafting be considered for patients with symptomatic patent ulnar artery aneurysms. Selected patients with thrombosed aneurysms with ongoing digital ischemia may also benefit from surgical intervention.

Adolescent↗
PubMed1999

Should patients who are suspected of having an ectopic pregnancy undergo physical examination?

OBJECTIVE: To determine whether physical examination is useful for patients with suspected ectopic pregnancy (EP) for whom transvaginal sonography is performed and serum hCG levels are measured. DESIGN: Prospective study. SETTING: Two large teaching hospitals. PATIENT(S): Three hundred eighty-two patients with suspected EP, based on a positive urine pregnancy test and the presence of abdominal pain, vaginal bleeding, or risk indicators. INTERVENTION(S): Abdominal examination, speculum inspection, and digital vaginal examination. MAIN OUTCOME MEASURE: A final diagnosis made by transvaginal sonography, serum hCG measurement, and, if necessary, confirmatory laparoscopy. RESULT(S): One hundred sixteen (30%) of the 382 patients had an EP. At external abdominal examination, rebound tenderness and muscular rigidity had likelihood ratios of 3.7 and 8.0, respectively. Findings at speculum inspection and digital vaginal examination had likelihood ratios between 0.33 and 2.4. Logistic regression analysis showed that the additional information provided by physical examination for the diagnosis of EP is limited compared with the information provided by transvaginal sonography and serum hCG measurement alone. CONCLUSION: On the basis of our results, we believe that vaginal digital examination for patients with suspected EP is unnecessary.

Adult↗
PubMed1995

Low-frequency spectral power of heart rate variability is not a specific marker of cardiac sympathetic modulation.

BACKGROUND: Heart rate variability in the frequency domain has been proposed to reflect cardiac autonomic control. Therefore, measurement of heart rate variability may be useful to assess the effect of epidural anesthesia on cardiac autonomic tone. Accordingly, the effects of preganglionic cardiac sympathetic blockade by segmental epidural anesthesia were evaluated in humans on spectral power of heart rate variability. Specifically, the hypothesis that cardiac sympathetic blockade attenuates low-frequency spectral power, assumed to reflect cardiac sympathetic modulation, was tested. METHODS: Ten subjects were studied while supine and during a 15-min 40 degrees head-up tilt both before and after cardiac sympathetic blockade by segmental thoracic epidural anesthesia (sensory block: C6-T6). ECG, arterial pressure, and respiratory excursion (Whitney gauge) were recorded, and a fast-Fourier-transformation was applied to 512-s data segments of heart rate derived from the digitized ECG at the end of each intervention. RESULTS: With cardiac sympathetic blockade alone and the subjects supine, both low-frequency (LF, 0.06-0.15 Hz) and high-frequency (HF, 0.15-0.80 Hz) spectral power remained unchanged. During tilt, epidural anesthesia attenuated the evoked increase in heart rate (+11.min-1 +/- 7 SD vs. +6 +/- 7, P = 0.024). However, while during tilt cardiac sympathetic blockade significantly decreased the LF/HF ratio (3.68 +/- 2.52 vs. 2.83 +/- 2.15, P = 0.041 vs. tilt before sympathetic blockade), a presumed marker of sympathovagal interaction, absolute and fractional LF and HF power did not change. CONCLUSIONS: Although preganglionic cardiac sympathetic blockade reduced the LF/HF ratio during tilt, it did not alter spectral power in the LF band during rest or tilt. Accordingly, low-frequency spectral power is unlikely to specifically reflect cardiac sympathetic modulation in humans.

Adult↗