Induced myocardial ischemia in candidates to liver transplantation without evidence of heart disease

BACKGROUND

Coronary artery disease (CAD) is associated with perioperative liver transplantation (LT) mortality. In absence of a defined risk algorithm, we aimed to test whether stress echocardiography and coronary computed tomography angiography (CCTA) could detect CAD in end-stage liver disease (ESLD) patients without previous evidence of heart disease.

METHODS

LT candidates ≥30 years underwent a cardiovascular (CV) assessment through stress echocardiography. CCTA was performed in patients ≥50 years with two or more CV risk factors (e.g. diabetes, CAD family history, dyslipidaemia). Coronary angiography (CAG) was scheduled when stress echocardiography and/or CCTA were positive. Sensibility, specificity, positive and negative predictive values of stress echocardiography and CCTA were assessed by numbers of coronary revascularization (true positives) and lack of acute coronary events over a mean follow-up of 3 years (true negatives).

RESULTS

Stress echocardiography was performed in 273 patients, CCTA in 34 and CAG in 41. Eight patients had critical coronary lesions, and 19 not-critical lesions. Sensitivity, specificity, positive and negative predictive values were 50.0%, 90.2%, 13.3% and 98.4% for stress echocardiography and 100%, 76.7%, 36.4% and 100% for CCTA. Among 163 patients who underwent LT (57.6%), 16 died and 5 had major adverse CV events over a mean follow-up of 3 years.

CONCLUSIONS

A very low prevalence of CAD in a selected population of ESLD at intermediate to high CV risk was found. A screening based on stress echocardiography and CCTA resulted in low incidence of post-LT acute coronary events in ELSD patients. CAD has no impact on mid-term survival.

Atrial fibrillation and ischemic heart disease: (un)solved therapeutic dilemma?

Concomitant presence of atrial fibrillation and coronary artery disease requiring percutaneous coronary intervention is a frequent occurrence. The choice of optimal antithrombotic therapy, in this context, is still challenging. To offer the best protection both in terms of stroke and stent thrombosis, triple therapy with oral anticoagulation and dual antiplatelet therapy would be required. Several drug combinations have been tested in recent years, including direct oral anticoagulants, with the aim of balancing ischemic and bleeding risk. Both pharmacokinetic aspects of the molecules and patient's characteristics should be analyzed in choosing oral anticoagulation. Then, as suggested by guidelines, triple therapy should start with a seven-day duration and the aim to prolong to thirty days in high thrombotic risk patients. Dual therapy should follow to reach twelve months after coronary intervention. Even not fully discussed by the guidelines, in order to balance ischemic and bleeding risk it should also be considered: 1) integrated assessment of coronary artery disease and procedural complexity of coronary intervention; 2) appropriateness to maintain the anticoagulant drug dosage indicated in technical data sheet; the lack of data on the suspension of antiplatelet drugs one year after percutaneous intervention; 3) the possibility of combination therapy with ticagrelor; and 4) the need to treat the occurrence of paroxysmal atrial fibrillation during acute coronary syndrome. With data provided clinician should pursue a therapy as personalized as possible, both in terms of drug choice and treatment duration, in order to balance ischemic and bleeding risk.

The "Woggle" Technique for Venous Access Site Management: An Old Technique for a New Need

BACKGROUND

Several closure devices are routinely used for percutaneous arterial access, while a relatively low number is available for the management of large bore venous accesses. The Woggle technique is a modification of the purse-string suture which was introduced several years ago in patients undergoing hemodialysis.

METHODS

A population of 45 patients who underwent transvenous femoral structural heart interventions was retrospectively evaluated. The Woggle technique consists of a purge string suture with a collar to maintain the tension as stable over time and a suture lock to tighten the suture.

RESULTS

Sheaths magnitude ranged from 8 French (F) to 14 F. A rapid post-procedural hemostasis was achieved in the whole population, and in 95% of cases, definite hemostasis was obtained after the first single release; the mean time of release was 302 ± 83 min. Although no relevant bleedings were reported, a significant reduction in hemoglobin levels was found in the whole population. This decrement was statistically significant only in the group with sheaths higher than 12 F. A single mild local hematoma was recorded in the group in which smaller sheaths were used. Seventy-two percent of patients were pre-treated with a dual antiplatelet therapy.

CONCLUSIONS

The Woggle technique has shown to be a simple, effective, and safe approach for the management of large bore venous in percutaneous structural heart interventions.

Right Heart Catheterization: An Antecubital Vein Approach to Reduce Fluoroscopy Time, Radiation Dose, and Guidewires Need

Antecubital access for right heart catheterization (RHC) is a widespread technique, even though there is a need to clarify if there are differences and significant advantages compared to proximal vein access. To pursue this issue, we retrospectively identified patients who underwent RHC in our clinic over a 7 year period (between January 2015 and December 2022). We revised demographic, anthropometric, and procedural data, including the fluoroscopy time, the radiation exposure, and the use of guidewires. The presence of any complications was also assessed. In patients with antecubital access, the fluoroscopy time and the radiation exposure were lower compared to proximal vein access (6 vs. 3 min, mean difference of 2 min, CI 95% 1-4 min, p < 0.001 and 61 vs. 30 cGy/m2, mean difference 64 cGy/m2, CI 95% 50-77, p < 0.001). The number of patients requiring the use of at least one guidewire was lower in the group undergoing RHC through antecubital access compared to proximal vein access (55% vs. 43%, p = 0.01). The feasibility was optimal, as just 0.9% of procedures switched from antecubital to femoral access, with a negligible rate of complications. The choice of the antecubital site exhibits advantages, e.g., a shorter fluoroscopy time, a reduced radiation dose, and a lower average number of guidewires used compared to proximal vein access.

P68 PERCUTANEOUS REVASCULARIZATION OF CORONARY CHRONIC OCCLUSIONS IN THE ELDERLY: EFFICACY AND SAFETY

Background

Percutaneous revascularization (PCI) of coronary total occlusions (CTO) is an effective treatment of refractory angina. This procedure presents higher procedural risks than routine PCI. For this reason PCI CTO is often not considered a viable option for elderly patients. The aim of the work is to evaluate the efficacy and safety of CTO PCI in a population over 75 years of age.

Materials and Methods

We considered patients undergoing CTO PCI from 2015 to 2021 in our center. Primary efficacy endpoint was the incidence of major adverse cardiovascular events (MACE) during follow–up in older subjects compared to younger subjects. Endpoints include target vessel revascularization (TVR), urgent non–target vessel revascularization, and cardiovascular death. Safety endpoints were considered complications intra–procedure, during hospitalization and 15 days after discharge. MACE–free survival rates were assessed with Kaplan–Meier analysis.

Results

127 patients were included, 30 aged more than 75 years (24%). The follow–up was 22 months. 86% were male. 32% were suffering from diabetes, 8% from chronic renal failure (creatinine &gt; 2 mg / ml), 76% from arterial hypertension, 40% were familiar with ischemic heart disease. No significant differences are reported in the distribution of risk factors between the two groups. The average age in younger group is 69 years compared to 79 in the elderly. In the follow–up, 16 MACE were found (1 death from cardiac arrest, 14 TVR, 1 non–target vessel revascularization). TVR was the most common endpoint, in 90% of cases this revascularization took place by election. Four events (13%) occurred in the group over 75 years and 12 cases (12%) in the other group (n = ns). Kaplan–Meier MACE–free survival rates were similar. Only 3 complications related to the procedure (2.5%) were reported and these are coronary perforations effectively managed in the hemodynamics room. The success rate of the revascularization procedure was similar (80% for those over 75 versus 82% for the younger group).

Conclusions

in our population age did not influence the efficacy and safety of CTO PCI which represents a valid option for refractory angina even in older patients.

P343 VALIDATION OF ESC 2014 GUIDELINES PROTOCOL FOR CORONARY ARTERY DISEASE DETECTION IN PATIENTS CANDIDATES TO LIVER TRANSPLANTATION

Introduction

Orthotopic liver transplantation (OLT) is the only effective treatment in patients with end–stage liver disease. Coronary artery disease (CAD) is associated with increased peri–operative OLT mortality. Thus, identification of CAD is crucial in pre–OLT evaluation. There is not a specific pre–OLT accepted diagnostic algorithm for CAD detection. 2014 ESC guidelines for non–cardiac surgery management consider OLT as a high–risk abdominal surgery and only patients with CAD history, suspected symptoms and low exercise capacity are invited to undergo to specific functional exams such as stress–echo.

Purpose of the present study was to compare the ESC protocol with our cardiologic pre–OLT protocol, in which tests of ischemia and coronary CT are largely administered on based on presence of risk factors. Methods. From 2014 to 2021 all OLT candidates have been evaluated by visit, electrocardiography, rest and, when possible, stress echocardiography. In subject aged &gt; 50 years with diabetes and/or two or more of the following risk factors: smoking, CAD family history, peripheral vascular disease, CT was performed. CGF was scheduled when CAD history and typical symptoms of angina. We theoretically re–analyse our database in order to consider the potential destiny of each patient in case of application of ECS 2014 protocol. We were able to calculate the differences in the number of potentially loss CAD diagnosis. Results. 367 patients (58.2%, age 57±5.7 years, males 74%) underwent OLT. Stress Echo was performed in 239 (65.1%) and positivity was found in 24 pz (6,5%). Coronary CT was performed in 95 (25,8%). CGF was performed in 75 patients (20.1%), 38 (9,2%) directly for known CAD and/or symptoms. Critical coronary lesions were found in 12 patients (3,2 %): 7 revascularized by PTCA, 1 by CABG and 4 medically managed, 25 patients had non critical lesions (7.8%), 31 patients (9.6%) referred to CGF were subsequently removed by transplant list, whereas OLT was successfully performed in PTCA patients (n = 8). During follow–up (35±20 months) 28 patients died (14.2%), 5 with symptoms of congestive heart failure, but no ischemic events were observed.

Conclusions

CAD detectionis remains a clinical challenge in candidates to OLT. The large number of normal stress echoes and normal CGF, even in presence of cardiovascular risk factors, demonstrates that CAD prevalence in ESLD is no higher than in general population, but a gold method to detect CAD is still unclear.

P213 ROLE OF ANEMIA AND IRON IMPLEMENTATION ON PROGNOSIS AND MANAGEMENT OF ELDERLY STEMI PATIENTS

Introduction

Elderly patients with S–T elevation myocardial infarction (STEMI) presented a very high risk for both in–hospital and long–term morbility and mortality. Comorbidities plays a key role in prognosis, in particular anemia (pre–existent or acquired) is a more and more emerging clinical element able to influence short– and long–term clinical outcome. Prognostic role of anemia in elderly STEMI patients in not completely clarified.

Purpose

of the present study is to evaluate the role of anemia and its therapy by iron implementation in a very–old population of STEMI patients followed for 1 year after index event.

Methods

we considered all STEMI patients admitted in our Coronary Care Unit from 2020 to 2021 and we selected only people aged &gt; 80 years–old (n = 120). Haemoglobin (Hb, g/dl) values were considered at admission (T0), at hospital discharge (T1) and after 6 month (T2). In hospital and 1 year mortality, treatment by primary PCI, major bleedings (TIMI criteria), need of transfusion, double antiplatelet therapy (DAPT) discontinuation, were considered and compared between groups of patients without and with anemia (A, Hb &lt; 13.5 for men and &lt;12 for women at T1) and without (NA group). Type of iron implementation (sucrosomial or not) and its tolerability were considered only for A group. Data were expressed as means±SD or % values.

Results

18 patients (15%) presented anemia at T0 (women 66%), 4 (22%) of them showed a TIMI major in–hospital bleeding (3, 20%, required blood transfusion) whereas 5 (5%) in non anemic, in–hospital mortality was similar between anemic and non–anemic (18% vs 17%). Sixteen (14%) presented mild anemia at T1 (14%, A group), mean age were similar to NA group (years, 86±4 vs 85±5, A vs NA, ns). In A 4 (25%) died during follow–up vs 11 (13%) in NA group during 1 year follow–up. Treatment with primary PTCA (31% vs 39%, A vs NA, ns) were similar. DAPT discontinuation In A group 16 patiens were discharged with indication to long–term iron implementation therapy, 6 of them with sucrosomial. Incidence of iron discontinuation was 16% (1 pt) for sucrosomial vs 50% (5 pts) for non–sucrosomial.

Conclusions

In elderly STEMI patients, 1) anemia at hospital admission influences in hospital major bleedings and need of blood trasfusions. 2) anemia at hospital discharge seems to affect DAPT discontinuation and long–term mortality. 3) use of sucrosomial iron reduces probability of discontinuation of implementation therapy.

P978 Acute myocardial infarction in young women without atherosclerotic disease

CONCLUSION

A high proportion of subjects presented with atypical challenging symptoms, while 30% were complicated with ventricular arrhythmias. This might be related to the high prevalence of proximal LAD dissection and anterior AMI in our subjects. An equal distribution of risk factors was recorded. No mortality events and no SCAD-recurrence were documented during follow up.

Abstract P978 Figure. Image 1

G-CSF for Extensive STEMI

RATIONALE

In the exploratory Phase II STEM-AMI (Stem Cells Mobilization in Acute Myocardial Infarction) trial, we reported that early administration of G-CSF (granulocyte colony-stimulating factor), in patients with anterior ST-segment-elevation myocardial infarction and left ventricular (LV) dysfunction after successful percutaneous coronary intervention, had the potential to significantly attenuate LV adverse remodeling in the long-term.

OBJECTIVE

The STEM-AMI OUTCOME CMR (Stem Cells Mobilization in Acute Myocardial Infarction Outcome Cardiac Magnetic Resonance) Substudy was adequately powered to evaluate, in a population showing LV ejection fraction ≤45% after percutaneous coronary intervention for extensive ST-segment-elevation myocardial infarction, the effects of early administration of G-CSF in terms of LV remodeling and function, infarct size assessed by late gadolinium enhancement, and myocardial strain.

METHODS AND RESULTS

Within the Italian, multicenter, prospective, randomized, Phase III STEM-AMI OUTCOME trial, 161 ST-segment-elevation myocardial infarction patients were enrolled in the CMR Substudy and assigned to standard of care (SOC) plus G-CSF or SOC alone. In 119 patients (61 G-CSF and 58 SOC, respectively), CMR was available at baseline and 6-month follow-up. Paired imaging data were independently analyzed by 2 blinded experts in a core CMR lab. The 2 groups were similar for clinical characteristics, cardiovascular risk factors, and pharmacological treatment, except for a trend towards a larger infarct size and longer symptom-to-balloon time in G-CSF patients. ANCOVA showed that the improvement of LV ejection fraction from baseline to 6 months was 5.1% higher in G-CSF patients versus SOC (P=0.01); concurrently, there was a significant between-group difference of 6.7 mL/m² in the change of indexed LV end-systolic volume in favor of G-CSF group (P=0.02). Indexed late gadolinium enhancement significantly decreased in G-CSF group only (P=0.04). Moreover, over time improvement of global longitudinal strain was 2.4% higher in G-CSF patients versus SOC (P=0.04). Global circumferential strain significantly improved in G-CSF group only (P=0.006).

CONCLUSIONS

Early administration of G-CSF exerted a beneficial effect on top of SOC in patients with LV dysfunction after extensive ST-segment-elevation myocardial infarction in terms of global systolic function, adverse remodeling, scar size, and myocardial strain.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01969890.

Dipyridamole stress echocardiography in diagnosis and prognosis of hemodialysis patients with asymptomatic coronary disease

The prevalence of coronary artery disease (CAD) is high in hemodialysis (HD) patients. The aim of the study was to assess the diagnostic and prognostic value of dipyridamole stress echocardiography (DSE) in nondiabetic HD patients without signs or symptoms of CAD. In 51 out of 158 evaluated HD patients (21 females, age 67 [33-85] years, HD duration 38 [9-271] months), resting echocardiography and DSE were performed. Exclusion criteria were known CAD, diabetes mellitus, and pulmonary and oncologic pathologies. Logistic regression analysis was carried out to identify predictors of abnormal DSE response, while Cox regression analysis was performed to determine variables associated with total and cardiovascular mortality, after 43.3 (11-60) months of follow-up. Seven patients (14%) showed a positive response to DSE (DSE+). In 5/7, CAD was documented by angiography: All of them underwent coronary revascularization. DSE+ patients had significantly smaller body mass index than patients with a negative response (DSE-): 21.7 ± 1.9 vs. 25.1 ± 3.4 kg/m(2) (p = 0.018). During follow-up, 16 (31%) patients died. Older age hazard ratio [HR = 1.07; confidence interval (CI) = 1.01-1.12; p = 0.02] and higher plasma phosphate levels (HR = 10.41; CI = 2.30-47.17; p < 0.01) were predictors of total mortality. Male gender (HR = 22.7; CI = 1.45-354.4; p = 0.03), older age (HR = 1.24; CI = 1.03-1.50; p = 0.02), longer HD duration (HR = 1.13; CI = 1.01-1.26; p = 0.04), and positive response to DSE (HR = 5.82; CI = 1.04-32.65; p = 0.04) were associated with cardiovascular mortality. Ten percent of asymptomatic HD patients had significant CAD, but timely diagnosis did not seem to improve their prognosis. Total survival was associated with age and higher levels of plasma phosphate, while male gender, older age, longer HD duration, and DSE+ were predictors of cardiovascular mortality.

Renal artery embolization for kidney trauma

Kidney trauma occurs in approximately 1-5% of all traumas with the male to female ratio being 3:1. In this paper we reported two cases of male patients with kidney trauma treated by renal artery embolization. Endo-vascular embolization is an efficient method for the treatment of patient with severe renal haemorrhage preserving loss of renal parenchyma and renal function.

Lowering of Elevated Ambulatory Blood Pressure by HMG-CoA Reductase Inhibitors

Controversial results were reported as to a possible blood pressure-lowering effect of statins. This may relate to methodological limitations (blood pressure measuring techniques) or to putative different effects of statins in different biologic conditions (cholesterol or blood pressure levels, age, etc). Patients with cholesterol>200 mg/dL and no previous statin treatment underwent 24-hour ambulatory blood pressure (ABP) monitoring and were classified as normotensives or hypertensives according to their ABP. They were randomized to statin (n=51, simvastatin or pravastatin, 10-20 mg/d; atorvastatin, 5-10 mg/d) or control treatment (n=23, soy lecithin, 20 g/d) for 2 months, after which ABP assessment was repeated. No consistent treatment-related reduction in ABP was observed in lecithin-treated patients (either hypertensives or normotensives) or in statin-treated normotensive patients (-0.7+/-5.1/-1.0+/-4.6 mm Hg, both P=ns). In contrast, statin-treated hypertensive patients showed lower systolic and diastolic blood pressure (-5.7+/-5.8/-3.5+/-3.9 mm Hg, both P<0.001), the effect was entirely accounted for by reduced daytime values with no change in nighttime values, and it was unrelated to the concomitant statin-induced cholesterol reduction. Statins moderately but significantly lower blood pressure in patients with high (but not with normal) ABP; the effect is confined to the daytime period and is unrelated to the extent of the cholesterol lowering.

Dynamic QT interval analysis in uraemic patients receiving chronic haemodialysis

OBJECTIVE

To analyse the duration of the QT interval and its relationship with heart rate changes in patients with uraemia, before and during haemodialysis.

METHODS

QT and RR intervals were measured automatically using a dedicated algorithm with 24-h Holter recordings in 29 patients (15 women) receiving chronic haemodialysis. QT corrected for heart rate (QTc) and the slope of QT/RR linear regression were calculated. Arterial blood pressure (ABP) was measured before and during haemodialysis. Plasma concentrations of K+, Mg2+ and Ca2+ were assessed before and after haemodialysis.

RESULTS

ABP decreased significantly from baseline (102.7 +/- 11.0 mmHg) during the first (100.6 +/- 8.8 mmHg, P < 0.05), second (95.6 +/- 10.6 mmHg, P < 0.05), and third (94.9 +/- 10.3 mmHg, P < 0.05) hours of haemodialysis. QTc was longer during haemodialysis than during a 4-h period of no dialysis (447 +/- 28 ms compared with 429 +/- 22 ms, P < 0.001), and increased progressively during haemodialysis, with the greatest value during the last hour of haemodialysis (454 +/- 32 ms compared with 426 +/- 22 ms, P < 0.001). QT/RR slopes and correlation coefficients were lower during haemodialysis than during the period of no dialysis (0.13 +/- 0.08 compared with 0.20 +/- 0.07, P < 0.001 and 0.48 +/- 0.30 compared with 0.81 +/- 0.20, respectively; P < 0.001), suggesting a reduced ability to adapt the QT interval in response to changes in heart rate. The effects of haemodialysis on QT interval and the QT/RR relationship were greater in women than in men. QTc variations during dialysis were not correlated with changes in ABP, but were inversely related to changes in Ca2+ concentration (r2 = 0.35; P = 0.001).

CONCLUSIONS

In patients with uraemia, the haemodialysis session induces a progressive increase in QT interval and modifies its relationship with heart rate. These effects may predispose some individuals to ventricular arrhythmias at the end of and immediately after the haemodialysis session.

Influence of left ventricular mass, uremia and hypertension on vagal tachycardic reserve

BACKGROUND

Left ventricular (LV) hypertrophy, arterial hypertension and end-stage renal disease (ESRD) are associated with deranged cardiac parasympathetic regulation and increased cardiovascular risk. These conditions often co-exist but little is known about the relative contribution of LV mass, arterial blood pressure and ESRD to impaired cardiac vagal tone. We evaluated the vagal tachycardic reserve (VTR) in subjects with normal renal function (age 58.4 +/- 6.6 years, n = 19) and in patients under chronic hemodialysis (HD) (age 62.6 +/- 13.2 years, n = 30) having wide ranges of LV mass and blood pressure.

METHODS

VTR was estimated from the tachycardic response to atropine (15 microg/kg intravenously) administered during a dipyridamole-atropine stress-echo test performed as part of the diagnostic work-up for identification of inducible myocardial ischemia. LV hypertrophy (defined as LV mass index > 125 g/m2 in both genders) was present in 20 HD patients and in nine control patients. Only patients free of inducible myocardial ischemia were included in the study.

RESULTS

The atropine-mediated tachycardia was: (i) significantly smaller in HD patients than in control patients (34.7 +/- 7.6 versus 60.8 +/- 10.5 beats/min, P < 0.01); (ii) independently and inversely related to LV mass (multiple regression; partial coefficients, -0.139 in HD patients and -0.382 in controls, both P < 0.01) and to mean blood pressure (-0.171 in HD patients and -0.268 in controls, both P < 0.01).

CONCLUSIONS

LV mass is the strongest (inverse) determinant of VTR. Blood pressure as well as the patient's renal status are also independent correlates of VTR, and the concomitance of LV hypertrophy and ESRD exacerbates the impairment of VTR.

Preservation of the baroreceptor heart rate reflex by chemical sympathectomy in experimental heart failure

BACKGROUND

The mechanisms underlying impaired baroreflex sensitivity in congestive heart failure (CHF) are incompletely understood. The purpose of the present study was to test the hypothesis that this alteration depends on the marked degree of sympathetic overactivity known to characterize the CHF syndrome.

METHODS AND RESULTS

Eight-week-old rats were subjected to induction of postmyocardial infarction CHF obtained by coronary ligation (Lig), chronic chemical sympathectomy by 6-hydroxydopamine (Sx), both interventions (Sx-Lig), or neither intervention (Veh-Sham, sham surgery, and vehicle administration). Four weeks after infarction, in conscious state, baroreflex sensitivity was assessed from the bradycardic responses to graded phenylephrine-induced elevations in blood pressure (BP). Left ventricular (LV) diameter was assessed by echocardiography, and plasma catecholamines were assayed to estimate sympathetic activity. Lungs were eventually excised and weighed (LW). CHF was associated with the following: (1) no changes in BP and heart rate; (2) sympathetic overactivity (norepinephrine, 320.2+/-53.8 pg/mL for Veh-Lig versus 173.4+/-20.5 pg/mL for Veh-Sham, P<0.01), prevented by Sx (181.2+/-35.5 pg/mL for Sx-Lig versus 159.8+/-33.1 pg/mL for Sx-Sham, P=NS); (3) LV enlargement (10.3+/-0.7 mm for Veh-Lig versus 6.8+/-0.6 mm for Veh-Sham, P<0.01), irrespective of Sx (9.7+/-0.7 mm for Sx-Lig versus 6.6+/-0.5 mm for Sx-Sham, P<0.01); (4) pulmonary congestion (LW, 7.55+/-0.40 mg per gram of body weight for Veh-Lig versus 5.21+/-0.44 mg per gram of body weight for Veh-Sham, P<0.01), marginally attenuated by Sx (6.54+/-0.28 mg per gram of body weight for Sx-Lig versus 4.98+/-0.22 mg per gram of body weight for Sx-Sham, P<0.05); (5) reduction in baroreflex sensitivity (0.443+/-0.032 ms/mm Hg for Veh-Lig versus 0.860+/-0.420 ms/mm Hg for Veh-Sham, P<0.01), entirely prevented by Sx (1.217+/-0.058 ms/mm Hg for Sx-Lig versus 1.345+/-0.093 ms/mm Hg for Sx-Sham, P=NS).

CONCLUSIONS

In early post-MI CHF, sympathectomy only partially attenuated LV dysfunction and entirely prevented baroreflex sensitivity impairment that arises from enhanced sympathetic activity.

Nitric oxide-dependent vasodilation and the regulation of arterial blood pressure

Conflicting evidence has been reported on the hypothesis that vascular nitric oxide (NO) release is modulated by autonomic influences. Another controversial question is whether an insufficient degree of NO-dependent vasodilation may play a contributory role in the genesis of arterial hypertension. To address these questions we evaluated NO-dependent vasodilation in conscious rats subjected to various experimental manipulations that interfere with autonomic function: chronic chemical sympathectomy (CCSx), acute ganglionic blockade (AGx) and chronic sinoaortic denervation (CSAD). Experiments were also carried out on 6- and 12-week-old spontaneously hypertensive rats (SHR) (i.e. during the pre-hypertensive and the early established hypertensive stage) and in age-matched Wistar-Kyoto (WKY) rats. Nitric oxide-dependent vasodilation was quantified from the extent of blood pressure (BP) elevation in response to acute inhibition of NO synthesis by L-nitromonomethyl-L-arginine (L-NMMA). Chronic chemical sympathectomy was produced by repeated 6-hydroxydopamine injections; AGx was induced by hexamethonium infusion; and CSAD was obtained by aortic nerve section and carotid sinus wall stripping. Nitric oxide synthesis inhibition by L-NMMA was followed by a marked BP elevation in all groups. Rats with CCSx, Agx or CSAD never showed reduced BP responses to L-NMMA compared to intact, control rats. Neither 6- nor 12-week-old SHR had attenuated pressor responses to L-NMMA compared to age-matched WKY rats. In conclusion, the data indicate that (i) in unanaesthetized quietly-behaving rats there is no significant modulation of NO release by autonomic influences and (ii) young SHR have unimpaired NO-dependent vasodilation so it is unlikely that a deficit of vascular NO release plays any etiologic role in the BP elevation of this experimental model.

Enhanced vascular reactivity in the sympathectomized rat: studies in vivo and in small isolated resistance arteries

OBJECTIVE

In the conscious rat, sympathectomy (6-hydroxydopamine pretreatment, 100 mg/kg intraperitoneally, twice in the previous 5-6 days) induces, among various homeostatic modifications, the frequent occurrence of sudden and wide oscillations of blood pressure. Since one of the mechanisms underlying this, as yet unexplained, phenomenon may be an enhanced vascular reactivity, we tested the hypothesis that sympathectomized rats exhibit such a hyper-reactivity. We examined the response to a variety of vasoactive agents both in vivo (chronically instrumented conscious animals) and in vitro (small isolated resistance arteries).

DESIGN AND METHODS

Wistar-Kyoto sympathectomized rats (6-hydroxydopamine pretreatment, n = 19) and control rats (vehicle pretreatment, n = 23) were studied. In conscious animals, concentration-blood pressure response curves to intra-venous bolus injections of vasopressin, phenylephrine and angiotensin II were obtained. In isolated vessels, concentration-wall tension response curves were obtained for norepinephrine, phenylephrine, vasopressin, serotonin and potassium. Vasodilator responses to acetylcholine (with or without L-NAME), bradykinin and sodium nitroprusside were also evaluated after precontraction with norepinephrine (mesenteric arteries) or vasopressin (cerebral arteries).

RESULTS

In sympathectomized rats in vivo the pressor responses to vasopressin, phenylephrine and angiotensin II were significantly larger than in control rats, the difference amounting to 46.5, 40.2 and 57.1%, respectively (all P < 0.05). In vitro, the vascular reactivity of isolated cerebral arteries was similar in sympathectomized and control rats. In contrast, the mesenteric arteries showed significantly increased contractions in sympathectomized compared to control rats in response to norepinephrine, phenylephrine and vasopressin but not to serotonin and potassium, whereas the vasodilator responses to acetylcholine and sodium nitroprusside (but not to bradykinin and acetylcholine+L-NAME) were reduced.

CONCLUSIONS

In conclusion, we showed that sympathectomy produces complex alterations of vascular reactivity both in vivo and in isolated vessels, which shift the balance of the sensitivity of the vessel between vasoconstrictor and vasodilating agents towards an increased constriction. These results are unlikely to simply reflect denervation supersensitivity; their underlying receptor, post-receptor and/or contractile mechanisms are yet to be identified.

Altered blood pressure variability in patients with congestive heart failure

OBJECTIVE

Congestive heart failure (CHF) is characterized by sympathetic overactivity but reduced variability of heart interval and sympathetic nerve activity; little information exists, however, about the alterations in blood pressure variability in this syndrome, especially during excitatory manoeuvres such as tilting or exercise.

DESIGN AND METHODS

Nine patients with CHF (age 62+/-1 years, NYHA class II-III, ejection fraction 33+/-1%, peak VO2 14.1+/-3.2 ml/min per kg body weight [mean +/- SEM]) and eight healthy control subjects (age 58+/-1 years) with normal left ventricular function were studied. Blood pressure (Finapres), R-R interval (ECG) and respiration (nasal thermistor) were recorded during 15-min periods of supine rest, 70 degree head-up tilting, submaximal bicycling exercise and post-exercise recovery. Total variance and the power of the spectral components of blood pressure (HF, respiratory-related; LF, 0.03-0.14 Hz; and VLF, 0.02-0.003 Hz) were measured.

RESULTS

Compared with control subjects, CHF patients have, first, a normal overall blood pressure variability during supine rest but a failure to increase this variability in response to head-up tilt and exercise; second, a suppressed LF spectral component of blood pressure at rest and in response to head-up tilt and exercise; and third, reappearance of LF blood pressure power during postexercise recovery.

CONCLUSIONS

In CHF patients, overall blood pressure variability and its LF spectral component are altered at rest and during sympathoexcitatory manoeuvres. Somewhat paradoxically, however, the depressed LF blood pressure power is partially restored during a 15-min recovery period, indicating that at least part of the CHF-related alterations of blood pressure variability have the potential to revert back towards normal under appropriate physiological circumstances.

Heart rate-dependent stiffening of large arteries in intact and sympathectomized rats

In the anesthetized rat, acute increases in heart rate are accompanied by a reduction in arterial distensibility, which is a significant phenomenon in elastic-type vessels such as the common carotid but much less evident in muscle-type vessels such as the femoral artery. Because the sympathetic nervous system importantly reduces arterial distensibility, the present study aimed to determine whether sympathetic influences (1) are involved in the heart rate-dependent changes in arterial distensibility and (2) exert differential effects on elastic-type versus muscle-type arteries. To address this issue, 9 sympathectomized (6-hydroxydopamine) and 10 vehicle-treated, 12-week-old, pentobarbitone-anesthetized Wistar-Kyoto rats were subjected to atrial pacing via a transjugular catheter at 5 different randomly sequenced rates (280, 310, 340, 370, and 400 bpm). After each step, spontaneous sinus rhythm was allowed to return to normal. Common carotid and femoral artery diameters were measured by an echo Doppler device (NIUS 01), and blood pressure was measured via catheter inserted into the contralateral vessel. Arterial distensibility was calculated over the systolic-diastolic pressure range according to the Langewouters formula. In the common carotid artery, progressive increases in heart rate determined progressive and marked reductions of distensibility (range, 15% to 43%) in sympathectomized and intact rats. In the femoral artery, the stiffening effect of tachycardia was present in sympathectomized rats (range, 21% to 42%), at variance with the inconsistent changes observed in intact rats. In conclusion, our experiments support the notions (1) that in predominantly elastic-type arteries, the stiffening effect of tachycardia is exerted independently of sympathetic modulation of the vessel wall properties and (2) that in predominantly muscle-type arteries, removal of sympathetic influences unmasks the stiffening effect of tachycardia.

Nitric oxide dependent vasodilation in young spontaneously hypertensive rats

Conflicting evidence exists on the possible impairment of tonic nitric oxide (NO) mediated vasodilation as a causative factor in the genesis of human as well as experimental hypertension. We evaluated the tonic NO-dependent vasodilation from the pressor response to NO synthesis inhibition by NG-monomethyl-L-arginine (L-NMMA) in 9 conscious, chronically instrumented spontaneously hypertensive rats (SHR) at 12 weeks of age, ie, during the early established hypertensive stage. Nine age-matched Wistar-Kyoto rats (WKY) were used as controls. The pressor responses to L-NMMA (100 mg . kg-1 IV bolus plus 1.5 mg . kg-1 . min-1 infusion for 60 minutes) as well as to non NO-dependent pressor stimuli, namely, vasopressin (2, 4, and 8 ng . kg-1) and phenylephrine (0.5, 1, and 2 microg . kg-1) given as IV boluses, were assessed both under control conditions and during suppression of autonomic reflexes by hexamethonium (30 mg . kg-1 IV bolus+1.5 mg . kg-1 . min-1 infusion). Rather than being reduced, the pressor responses to L-NMMA were 39% and 71% larger in the control and areflexic conditions, respectively, than those observed in WKY (both P<0.01). A similar pattern was observed for the pressor responses to vasopressin (+37% and +68% in the control and areflexic conditions, respectively; both P<0.01) and phenylephrine, (+20% and +52%; both P<0.05). Additional groups of 6-week-old prehypertensive SHR (n=11) and age-matched WKY (n=11) were subjected to an identical protocol: in these animals, the pressor responses to L-NMMA were similar in each strain, as were the pressor responses to vasopressin and phenylephrine in both control and areflexic conditions. In conclusion, our observations indicate that during the developmental phase of hypertension in the SHR model, namely, during the prehypertensive as well as the early established hypertensive stage, NO-dependent vasodilation is preserved (if not enhanced) so that a putative impairment of this function provides no significant pathogenic contribution to the onset of hypertension in this experimental model.

Age-dependent expression of fibrosis-related genes and collagen deposition in the rat myocardium

OBJECTIVES

We sought to characterize the evolution, during maturational growth and early ageing, of the messenger abundance of four genes involved in cardiac fibrosis regulation (procollagens alpha2(I) and alpha1(III), transforming growth factors beta1, and beta3) and corroborate it with the alterations in collagen deposition in cardiac interstitium and around coronary arteries.

METHODS

Messenger RNA was quantified in LV and RV of 2-, 6-, 12- and 19-month-old male Sprague-Dawley rats (n = 5 per group) with Northern blot analysis. Collagen deposition was quantified with a semi-automated image analyser on Sirius red-stained sections of LV tissue.

RESULTS

There was an age-related monotonous decrease of procollagen type I (COL-I) transcript abundance in LV (p < 0.001) but not in RV. Procollagen type III (COL-III) expression decreased rapidly during maturational growth, both in LV and RV. On the other hand, collagen deposition in myocardial interstitium and around coronary arteries was slightly augmented during the maturational period of life (2-12 months), but with a higher rate during early ageing (up to 19 months). This was not accompanied by a significant thickening of the wall of coronary arteries. Transforming growth factor beta1, (TGF-beta1) and transforming growth factor beta3 (TGF-beta3) transcript abundance showed no major variations during ageing.

CONCLUSIONS

These results reflect a striking ventricular difference regarding the age-dependent expression of COL-I. The expression of TGF-beta(s), pleiotropic factors known to influence collagen pathway at different levels, does not seem to be profoundly altered during ageing. The discrepancy between protein and COL-I and COL-III mRNA levels indicates differences in age-related mRNA stability and/or regulation of collagen translation.

Lack of autonomic contributions to tonic nitric oxide-mediated vasodilatation in unanesthetized free-moving rats

OBJECTIVE

To clarify the controversial issue of whether autonomic influences modulate vascular nitric oxide-mediated vasodilatation or even directly contribute to production of nitric oxide (NO) via nitroxidergic fibers.

METHODS

Chronic venous and arterial catheters were implanted in Wistar-Kyoto rats (n = 65) for continuous blood pressure measurement, drug administration and blood sampling. Tonic NO-dependent vasodilatation in the conscious free-moving animal was evaluated as the pressor response to inhibition of NO synthesis by intravenous L-monomethylarginine (a 100 mg/kg intravenous bolus plus 0.5 mg/kg per min infusion for 30 min). Experiments were performed under control conditions, chemical sympathectomy by 6-hydroxy-dopamine, ganglionic blockade by hexamethonium, and surgical denervation of sino-aortic baroreceptors.

RESULTS

Baseline mean arterial pressure was 100+/-4 mmHg (mean +/- SEM) in control rats and 73+/-3, 62+/-5, and 105+/-10 mmHg in sympathectomized, ganglion-blocked, and denervated rats, respectively. The peak increase in mean arterial pressure after administration of L-monomethylarginine was 38+/-3 mmHg in control rats and 51+/-3, 50+/-6, and 63+/-10 mmHg in sympathectomized, ganglion-blocked, and denervated rats, respectively. Epinephrine and norepinephrine levels in rats of separate groups of unanesthetized control, sympathectomized and ganglion-blocked animals were measured by high-performance liquid chromatography from an arterial blood sample, the results indicating drastic reductions in levels of both catecholamines in the ganglion-blocked (but not in the sympathectomized) rats compared with those in the control rats.

CONCLUSIONS

Tonic NO-dependent vasodilatation can normally be maintained in the unanesthetized unrestrained rat irrespective of autonomic or humoral adrenergic influences.

Differential alterations of common carotid and femoral artery distensibility in 12-week-old spontaneously hypertensive rats

OBJECTIVE

In essential hypertension, the mechanical properties of the radial artery have been shown to be largely unaltered, whereas more controversial and less reliable data have been obtained for the common carotid artery. We therefore examined the distensibility/pressure relationships of the predominantly elastic common carotid artery and of the predominantly muscle-type femoral artery in 12-week-old normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR).

METHODS

Eleven 12-week-old SHR and 10 age-matched WKY rats were anesthetized with sodium pentobarbitone. Blood pressure and pulse rate were measured by catheters inserted in the common carotid and in the femoral arteries, while contralateral arterial diameter was continuously recorded via an echo-tracking device. Arterial compliance was derived according to the Langewouters formula, and its values were normalized for the diameter, to obtain distensibility/pressure curves and to calculate the distensibility index. The Peterson elastic modulus was also calculated in order to obtain a pressure-independent estimate of arterial mechanical properties.

RESULTS

Femoral artery distensibility/pressure curves and distensibility index were similar in the two groups of rats, the latter being 1.13+/-0.13 mm/mmHg10(-3) in SHR and 1.28+/-0.15 mm/mmHg10(-3) in WKY rats (means+/-SEM; NS). In contrast, in SHR, common carotid artery mechanical properties were clearly impaired, as shown by a marked reduction in distensibility index (2.55+/-0.16 mm/mmHg10(-3) in SHR versus 3.4+/-0.3 mm/mmHg10(-3) in WKY rats; P< 0.05), and by a significant increase in the Peterson elastic modulus.

CONCLUSIONS

In the SHR model, high blood pressure alters the mechanics of large arteries even in the relatively early stage of the disease; however, the alterations are not homogeneous inasmuch elastic-type vessels are affected to a much greater extent than muscle-type vessels.

Effect of sympathectomy on mechanical properties of common carotid and femoral arteries

Sympathetic stimulation is accompanied by a reduction of arterial distensibility, but whether and to what extent elastic and muscle-type arterial mechanics is under tonic sympathetic restraint is not known. We addressed this issue by measuring, in the anesthetized rat, the diameters of the common carotid and femoral arteries with an echo-Doppler device (NIUS 01). Blood pressure was measured by a catheter inserted contralaterally and symmetrically to the vessel where the diameter was measured. Arterial distensibility over the systolic-diastolic pressure range was calculated according to the Langewouters formula. Data were collected in 10 intact (vehicle pretreatment) and 9 sympathectomized (6-hydroxydopamine pretreatment) 3-month-old Wistar-Kyoto rats. Compared with the intact animals, sympathectomized rats showed a marked increase in arterial distensibility over the entire systolic-diastolic pressure range. When quantified by the area under the distensibility-pressure curve, the increase was 59% and 62% for the common carotid and femoral arteries, respectively (P<.01 for both). In the femoral but not in the common carotid artery, sympathectomy was accompanied also by an increase in arterial diameter (+18%, P<.05 versus intact). Therefore, in the anesthetized normotensive rat, sympathetic activity exerts a tonic restraint on large-artery distensibility. This restraint is pronounced in elastic vessels and even more pronounced in muscle-type vessels.

Heart rate-dependence of arterial distensibility in vivo

OBJECTIVES

Viscous and inertial components contribute to arterial distensibility and compliance in vitro. The purpose of our study was to determine whether this phenomenon is of relevance in vivo, namely, whether arterial compliance is altered by an increase in heart rate.

DESIGN

Arterial diameter was assessed by an echo-Doppler device in a common carotid and femoral artery, namely, in a large elastic and a muscle artery. The studies were performed in 12-week-old pentobarbitone-anaesthetized Wistar-Kyoto rats subjected to atrial pacing via a transjugular unipolar catheter at five different randomly sequenced rates (280, 310, 340, 370 and 400 beats/min). After each stage, spontaneous sinus rhythm was allowed to return. Blood pressure was measured via a catheter inserted into the carotid or femoral artery contralateral to the vessels in which the diameter was measured. Arterial compliance and distensibility values were derived according to the Langewouters formula.

RESULTS

A progressive increase in heart rate caused by pacing was accompanied by progressive and marked reductions in carotid artery compliance and distensibility. When quantified by the area under the distensibility-pressure or compliance-pressure curve the reduction was in the range 15-43%. Although a tendency to a similar phenomenon was observed in the femoral artery, in the latter vessel the reduction in distensibility and compliance was less marked and statistically insignificant.

CONCLUSIONS

In the anaesthetized rat acute increases in heart rate are accompanied by reductions in arterial compliance and distensibility. The effect is greater in elastic than in muscle arteries.

Reproducibility of ultrasound assessment of common carotid and femoral artery compliance and distensibility in the anesthetized rat

OBJECTIVE

To validate ultrasound assessment of common carotid and femoral artery compliance and distensibility in the anesthetized rat.

MATERIALS AND METHODS

A reproducibility study was performed by taking measurements twice on two different days in anesthetized Wistar-Kyoto (WKY) rats. The common carotid or femoral arterial diameter on one side and the contralateral arterial blood pressure were measured using a 10-MHz probe echo-Doppler device and an arterial catheter, respectively. The pressure and diameter data were stored in a computer programmed to calculate the arterial compliance and distensibility coefficients (Reneman formulas) and compliance and distensibility indices (arctangent model of Langewouters). A second experimental session was repeated 1 day later, and mean values, day-to-day mean differences and repeatability coefficients were calculated for each parameter.

RESULTS

For both the common carotid and the femoral artery, the mean values for heart rate, mean arterial pressure, arterial diameter, arterial compliance and arterial distensibility were similar on the first and second days; mean day-to-day differences were small and repeatability coefficients were in the range 5-10% of the mean value for diameter and mean arterial pressure and 10-20% of the mean value for compliance and distensibility.

CONCLUSIONS

In the anesthetized rat, ultrasound evaluation of the mechanical properties of the common carotid and femoral arteries is a reliable and reproducible technique.