Automated Impedance Cardiography for Detecting Ischemic Left Ventricular Dysfunction during Exercise Testing

Cardiac hemodynamics phenotypes and individual responses to training in coronary heart disease patients

BACKGROUND

In patients with coronary heart disease (CHD), individualized exercise training (ET) programs are strongly recommended to optimize peak oxygen uptake (V ̇ $$ \dot{\mathrm{V}} $$ O2peak) improvement and prognosis. However, the cardiac hemodynamic factors responsible for a positive response to training remain unclear. The aim of this study was to compare cardiac hemodynamic changes after an ET program in responder (R) versus non-responder (NR) CHD patients.

METHODS

A total of 72 CHD patients completed a 3-month ET program and were assessed by cycle ergometer cardiopulmonary exercise test (CPET:V ̇ $$ \dot{\mathrm{V}} $$ O2peak assessment) with impedance cardiography (ICG) for hemodynamic measurements before and after training. Cardiac hemodynamics (e.g., CO, CI, SV, ESV, EDV, and SVR) were measured by ICG during CPET. The R and NR groups were classified using the median change inV ̇ $$ \dot{\mathrm{V}} $$ O2peak (>the median for R and ≤the median for NR).

RESULTS

In the R group,V ̇ $$ \dot{\mathrm{V}} $$ O2peak (+17%, p < 0.001), CO, CI, SV, and HR increased by 17%, 17%, 13%, and 5%, respectively (p < 0.05) after the training program. In the NR group,V ̇ $$ \dot{\mathrm{V}} $$ O2peak, CO, CI, and SV increased by 0.5%, 5%, 8%, and 6%, respectively (p < 0.01). The SVR decreased in both groups (-19% in R and -11% in NR, p < 0.001).

CONCLUSION

Among CHD patients, the R group showed a better improvement in peak cardiac output via an increase in peak stroke volume and heart rate and a reduced systemic vascular resistance than the NR group. Different cardiac phenotype adaptations and clinical individual responses were identified in CHD patients according to the aerobic fitness responder's status.

Cognitive function in patients with stable coronary heart disease: Related cerebrovascular and cardiovascular responses

Chronic exercise has been shown to prevent or slow age-related decline in cognitive functions in otherwise healthy, asymptomatic individuals. We sought to assess cognitive function in a stable coronary heart disease (CHD) sample and its relationship to cerebral oxygenation-perfusion, cardiac hemodynamic responses, and V˙O2 peak compared to age-matched and young healthy control subjects. Twenty-two young healthy controls (YHC), 20 age-matched old healthy controls (OHC) and 25 patients with stable CHD were recruited. Cognitive function assessment included short term—working memory, perceptual abilities, processing speed, cognitive inhibition and flexibility and long-term verbal memory. Maximal cardiopulmonary function (gas exchange analysis), cardiac hemodynamic (impedance cardiography) and left frontal cerebral oxygenation-perfusion (near-infra red spectroscopy) were measured during and after a maximal incremental ergocycle test. Compared to OHC and CHD, YHC had higher V˙O2 peak, maximal cardiac index (CI max), cerebral oxygenation-perfusion (ΔO₂ Hb, ΔtHb: exercise and recovery) and cognitive function (for all items) (P<0.05). Compared to OHC, CHD patients had lower V˙O2 peak, CI max, cerebral oxygenation-perfusion (during recovery) and short term—working memory, processing speed, cognitive inhibition and flexibility and long-term verbal memory (P<0.05). V˙O2 peak and CI max were related to exercise cerebral oxygenation-perfusion and cognitive function (P<0.005). Cerebral oxygenation-perfusion (exercise) was related to cognitive function (P<0.005). Stable CHD patients have a worse cognitive function, a similar cerebral oxygenation/perfusion during exercise but reduced one during recovery vs. their aged-matched healthy counterparts. In the all sample, cognitive functions correlated with V˙O2 peak, CI max and cerebral oxygenation-perfusion.

Exercise Lowers Plasma Angiopoietin-Like 2 in Men with Post-Acute Coronary Syndrome

Pro-inflammatory angiopoietin-like 2 (angptl2) promotes endothelial dysfunction in mice and circulating angptl2 is higher in patients with cardiovascular diseases. We previously reported that a single bout of physical exercise was able to reduce angptl2 levels in coronary patients. We hypothesized that chronic exercise would reduce angptl2 in patients with post-acute coronary syndrome (ACS) and endothelial dysfunction. Post-ACS patients (n = 40, 10 women) were enrolled in a 3-month exercise-based prevention program. Plasma angptl2, hs-CRP, and endothelial function assessed by scintigraphic forearm blood flow, were measured before and at the end of the study. Exercise increased VO₂peak by 10% (p<0.05), but did not significantly affect endothelial function, in both men and women. In contrast, exercise reduced angptl2 levels only in men (-26±7%, p<0.05), but unexpectedly not in women (+30±16%), despite similar initial levels in both groups. Exercise reduced hs-CRP levels in men but not in women. In men, levels of angptl2, but not of hs-CRP, reached at the end of the training program were negatively correlated with VO₂peak (r = -0.462, p = 0.012) and with endothelial function (r = -0.419, p = 0.033) measured at baseline: better initial cardiopulmonary fitness and endothelial function correlated with lower angptl2 levels after exercise. Pre-exercise angptl2 levels were lower if left ventricular ejection time was long (p<0.05) and the drop in angptl2 induced by exercise was greater if the cardiac output was high (p<0.05). In conclusion, in post-ACS men, angptl2 levels are sensitive to chronic exercise training. Low circulating angptl2 reached after training may reflect good endothelial and cardiopulmonary functions.

Cardiovascular changes occurring with occlusion of a mature arteriovenous fistula

Background

The aim of this study was to evaluate the relationship between Qa, cardiovascular parameters and symptomatic cardiac disease.

Methods

A prospective cohort study of 100 patients dialysing via an arteriovenous fistula (AVF) was performed. Qa was measured using pulsed Doppler ultrasound. Cardiovascular parameters were measured using thoracic bioimpedance technique (Medis, GmbH). Measurement of cardiovascular parameters was undertaken pre- and post-occlusion of the AVF.

Results

Mean age was 57.1 years (range: 19-83); 51% male. Mean values pre-occlusion: mean arterial blood pressure (MABP) 89.6 ± 16.9 mmHg; stroke volume index (SVI) 39.3 ± 4.6 mL; cardiac index (CI) 3.7 ± 0.8 L/min/m2; systemic vascular resistance index (SVRI) 585.5 ± 67.8 dyn/sec/cm−5/m2; oxygen delivery (DO2I) 607.1 ± 116.8 mL/min/m2. A total of 12% of patients had CI>4.5 L/min/m2 pre-occlusion. There was no difference in heart rate (HR), MABP and SVI following occlusion of AVF. Mean CI reduced post-AVF occlusion (∆CI: -0.42 L/min/m2; p<0.001), as did DO2I (∆ DO2I: 45.5 mL/min/m2; p<0.001). SVRI increased (∆SVRI: 170.1 dyn/sec/cm−5/m2; p<0.001). The drop in CI which occurred post-AVF occlusion was greater in patients with Qa >2000 mL/min (-2.79 ± 0.34 vs. -0.24 ± 0.48 L/min/m2; p<0.001). There was a non-significant trend towards symptomatic heart failure in those patients with a greater ∆CI following AVF occlusion (NYHA 1: -0.1 ± 0.1 L/min/m2; NHYA 2: -0.3 ± 0.7 L/min/m2; NYHA 3: -0.7 ± 1.0 L/min/m2; p = 0.06).

Conclusions

The relationship between AVF blood flow, cardiac output and symptomatic cardiac disease is complex. Occlusion of an AVF leads to reduced cardiac output and improved oxygen delivery, even in asymptomatic patients. This difference is most marked in patients with high-flow AVF (>2000 mL/min). High-flow AVF with large ∆CI may lead to high cardiac output state, which is reversible on occlusion of the AVF.