Simultaneous echocardiographic evaluation of coronary flow velocity reserve and aortic distensibility indices in hypertension

Impaired aortic distensibility in hypothyroid patients with negative coronary angiograms: Simultaneous evaluation with 128-slice multiple row detector computed tomography

Objective

To determine the relationship between arterial distensibility and hypothyroidism by simultaneous assessment of coronary angiography and aortic distensibility, measured using 128-slice retrospective electrocardiogram-gated multiple row detector computed tomography (MDCT).

Methods

Untreated hypothyroid patients and age-matched euthyroid patients, who underwent 128-slice retrospective electrocardiogram-gated MDCT to evaluate the coronary arteries, were assessed. Intraluminal aortic areas in systolic and diastolic phases of the cardiac cycle were measured with multiphase reformation at predefined locations including the ascending aorta, proximal descending aorta and distal descending aorta in the widest axial plane.

Results

The study included 21 hypothyroid and 21 euthyroid patients. Patients with hypothyroidism exhibited decreased aortic distensibility between each location in the thoracic aorta (ascending aorta, proximal descending aorta and distal descending aorta) compared with euthryoid patients.

Conclusions

Hypothyroidism was associated with preclinical vascular alteration, characterized by impaired aortic distensibility at each location of the thoracic aorta, which has been shown to be related to increased cardiovascular risk. Monitoring of aortic distensibility is relevant for evaluating coronary artery disease progression and treatment choices.

Echocardiographic evaluation and clinical implications of aortic stiffness and coronary flow reserve and their relation

The normal human aorta is not a stiff tube but is characterized by elastic properties with a buffering Windkessel function. Aortic stiffening may cause an increase in aortic pulse pressure, left ventricular load, and ultimately left ventricular hypertrophy. This, together with the decreased diastolic transmyocardial pressure gradient interacts with coronary flow and flow reserve. In recent studies, significant correlations between coronary flow reserve and aortic stiffness have been demonstrated in different patient populations. The aim of the present review is to describe the current echocardiographic modalities to measure aortic stiffness and coronary flow reserve and to overview our knowledge about the relationship between aortic stiffness and coronary flow reserve.

Diminished coronary flow velocity reserve and aortic distensibility in elderly patients with chest pain and negative coronary angiograms

BACKGROUND AND AIMS

Aging is a dominant process that alters vascular stiffness, endothelial function and coronary flow regulation. The objective of our work was to assess simultaneously the elastic properties of the descending aorta and coronary flow velocity reserve (CFR) during the same transesophageal echocardiography (TEE) in elderly patients.

METHODS

The following patients with normal epicardial coronary arteries were compared: 30 subjects under 55 years of age (group 1) and 17 patients over 55 years (group 2). A complete TEE examination was carried out in all patients, and the following aortic elastic properties were calculated from aortic diameter and blood pressure data: aortic elastic modulus [E(p)] and Young's circumferential static elastic modulus [E(s)]. Doppler evaluation of left anterior descending coronary flow velocity was performed in resting conditions and after administration of 0.56 mg/Kg dipyridamole over 4 min. Peak coronary flow velocities were measured at the 6th minute at maximum vasodilation. CFR was estimated as the ratio of hyperemic to basal peak diastolic coronary flow velocities.

RESULTS

Peak hyperemic diastolic coronary flow velocities were significantly decreased (139.1+/-35.6 cm/s vs 105.7+/-39.7 cm/s, p<0.01) in patients >55 years. CFR was decreased (2.67+/-1.05 vs 2.13+/-0.56, p<0.05), whereas E(p) (in 103 mmHg, 0.59+/-0.49 vs 0.94+/-0.65, p<0.05) and E(s) (in 103 mmHg, 5.70+/-4.30 vs 8.47+/-5.14, p<0.05) were increased in patients >55 years. A correlation was found between CFR and E(p) (r=-0.20, p<0.05).

CONCLUSIONS

CFR and aortic distensibility are altered in elderly patients. There is a relationship between these functional parameters.

Comparison of coronary flow velocity reserve and aortic distensibility in diabetic versus non-diabetic patients with and without aortic atherosclerosis

Coronary flow velocity reserve (CFR) and aortic distensibility are altered both in diabetes and in the presence of aortic atherosclerosis (AA). Transoesophageal echocardiography has been demonstrated to be a suitable method for simultaneous evaluation of these functional parameters. In the present study no significant difference could be observed in CFR and aortic distensibility in diabetic patients compared to non-diabetic subjects with or without AA.

Insulin resistance functionally limits endothelium-dependent coronary vasodilation in nondiabetic patients

Insulin resistance (IR) is now considered to be a risk factor for coronary arterial atherosclerosis and is likely to be involved in a limited endothelium-dependent vasodilatory function in peripheral circulation. We investigated whether IR impairs endothelial vasodilator function in the noninfarcted coronary artery. In 14 nondiabetic patients (10 males, 66 +/- 6 years) who were selected from 214 patients underwent IR evaluation by glucose clamp, a Doppler flow wire was used to measure coronary flow changes (percent volume flow index, %VFI) during intracoronary administration of papaverin (10 mg) and stepwise administration of acetylcholine (Ach; 1, 3, 10 microg/ml per minute) into the non-infarcted left circumflex coronary artery. Insulin resistance was comparatively evaluated by an euglycemic hyperinsulinemic glucose clamp (M value, mg/m(2) per minute) or by a 75g-oral glucose tolerance test (120-min immunoreactive insulin; 120' IRI, pmol/l). Eight patients (57%) were defined as having IR on the basis of results obtained by both the glucose clamp method (M values <167 mg/m(2) per minute) and 120' IRI (>384 pmol/l). There was no difference between papaverin-induced %VFI increases in IR and non-IR subjects (328% +/- 43% vs. 361% +/- 87%). However, IR subjects showed significantly lower Ach-induced %VFI increases in a dose-dependent manner (P < 0.05), especially when low (1 microg/ml per minute) and moderate (3 microg/ml per minute) doses of Ach were used (165% +/- 18% or 248% +/- 29% in non-IR subjects vs. 130% +/- 20% or 183% +/- 41% in IR subjects, P < 0.001, respectively). Moreover, %VFI increase at a low dose of Ach infusion significantly correlated with M values or 120' IRI ([%VFI Ach 1 microg] = 85.9 + 0.35 [M values], r = 0.58, P = 0.038; [%VFI Ach 1 microg] = 176.8 - 0.47.[120' IRI], r = -0.57, P = 0.035). Insulin resistance limits endothelium-dependent coronary vasodilation in association with the severity of IR in non-diabetic patients.

Reduction of coronary flow reserve in patients with increased aortic stiffness

Aortic stiffness is thought to affect coronary blood flow, but little is known about its influence on coronary flow reserve (CFR). The objective of the present study was to investigate the relationship between aortic stiffness and CFR in matched patients with and without increased aortic stiffness. Stress transoesophageal echocardiography (TEE) as the CFR measurement and coronary angiography were performed in all cases. Increased aortic stiffness was defined if elastic modulus Ep > 680 mmHg. The following patient populations free of coronary artery disease were compared: 36 subjects with normal aortic distensibility and 19 age-, sex-, and risk factor-matched patients with increased aortic stiffness. CFR was significantly reduced in patients with increased aortic stiffness as compared with cases with normal aortic distensibility (2.64 ± 1.16 vs. 2.12 ± 0.58, p <0.01). Hyperaemic diastolic flow velocities were reduced in patients with increased aortic stiffness (129.5 ± 36.6 cm/s vs. 102.1 ± 39.8 cm/s, p <0.05). Negative correlations were found between Ep and hyperaemic diastolic coronary flow velocity (r = –0.41, p < 0.01) and CFR (r = –0.21, p < 0.05). CFR is reduced in patients with increased aortic stiffness and negative correlations exist between these functional parameters.