Coronary blood flow in heart failure: cause, consequence and bystander

Heart failure is a clinical syndrome where cardiac output is not sufficient to sustain adequate perfusion and normal bodily functions, initially during exercise and in more severe forms also at rest. The two most frequent forms are heart failure of ischemic origin and of non-ischemic origin. In heart failure of ischemic origin, reduced coronary blood flow is causal to cardiac contractile dysfunction, and this is true for stunned and hibernating myocardium, coronary microembolization, myocardial infarction and post-infarct remodeling, possibly also for the takotsubo syndrome. The most frequent form of non-ischemic heart failure is dilated cardiomyopathy, caused by genetic mutations, myocarditis, toxic agents or sustained tachyarrhythmias, where alterations in coronary blood flow result from and contribute to cardiac contractile dysfunction. Hypertrophic cardiomyopathy is caused by genetic mutations but can also result from increased pressure and volume overload (hypertension, valve disease). Heart failure with preserved ejection fraction is characterized by pronounced coronary microvascular dysfunction, the causal contribution of which is however not clear. The present review characterizes the alterations of coronary blood flow which are causes or consequences of heart failure in its different manifestations. Apart from any potentially accompanying coronary atherosclerosis, all heart failure entities share common features of impaired coronary blood flow, but to a different extent: enhanced extravascular compression, impaired nitric oxide-mediated, endothelium-dependent vasodilation and enhanced vasoconstriction to mediators of neurohumoral activation. Impaired coronary blood flow contributes to the progression of heart failure and is thus a valid target for established and novel treatment regimens.

The role of protein kinase C and PI3-kinase in the mechanism of the cardioprotective effect of remote ischemic postconditioning

Background. Acute myocardial infarction (AMI) with ST segment elevation is associated with high incidence of complications. Mortality from AMI is about 5%, which has not decreased in recent years. Revascularization provides recovery of coronary blood flow, but also contributes to the occurrence of reperfusion injury to the heart. Remote ischemic postconditioning (RIPostC) is a promising, non-invasive method that can effectively and safely reduce the infarct size.The aim of the study was to investigate the role of protein kinase C and PI3-kinase in the development of the infarct-limiting effect of remote ischemic postconditioning.Materials and methods. The study was performed on Wistar rats. Coronary artery occlusion (45 min) and reperfusion (2 h) were performed. The infarct size (IS) and the size of area at risk (AAR) were assessed. RIPostC was modeled by applying tourniquets to the hind limbs in the hip joint immediately after the restoration of coronary blood flow. All inhibitors were administered intravenously 10 min before reperfusion.Results. In the control group, the IS / AAR ratio was 44%. RIPostC reduced the IS / AAR ratio by about 50%. Preliminary administration of the protein kinase C inhibitor chelerythrine and the PI3-kinase inhibitor wortmannin eliminated the cardioprotective effect of RIPostC.Conclusion. The mechanism of the infarct-limiting effect of RIPostC is implemented through activation of protein kinase C and PI3-kinase.

Early Hyperdynamic Sepsis Alters Coronary Blood Flow Regulation in Porcine Fecal Peritonitis

Background: Sepsis is a common condition known to impair blood flow regulation and microcirculation, which can ultimately lead to organ dysfunction but such contribution of the coronary circulation remains to be clarified. We investigated coronary blood flow regulatory mechanisms, including autoregulation, metabolic regulation, and endothelial vasodilatory response, in an experimental porcine model of early hyperdynamic sepsis.Methods: Fourteen pigs were randomized to sham (n = 7) or fecal peritonitis-induced sepsis (n = 7) procedures. At baseline, 6 and 12 h after peritonitis induction, the animals underwent general and coronary hemodynamic evaluation, including determination of autoregulatory breakpoint pressure and adenosine-induced maximal coronary vasodilation for coronary flow reserve and hyperemic microvascular resistance calculation. Endothelial-derived vasodilatory response was assessed both in vivo and ex vivo using bradykinin. Coronary arteries were sampled for pathobiological evaluation.Results: Sepsis resulted in a right shift of the autoregulatory breakpoint pressure, decreased coronary blood flow reserve and increased hyperemic microvascular resistance from the 6th h after peritonitis induction. In vivo and ex vivo endothelial vasomotor function was preserved. Sepsis increased coronary arteries expressions of nitric oxide synthases, prostaglandin I2 receptor, and prostaglandin F2α receptor.Conclusion: Autoregulation and metabolic blood flow regulation were both impaired in the coronary circulation during experimental hyperdynamic sepsis, although endothelial vasodilatory response was preserved.

Recurrent Takotsubo syndrome complicated with ischemic enteritis successfully treated by hydration: a case report

Background Takotsubo syndrome is a sudden and an acute form of transient cardiac dysfunction, triggered by mental and physical stress. The treatment for Takotsubo syndrome is not well understood and is incompletely established. Takotsubo syndrome is partly thought to be caused by coronary ischemia under sympathetic nerve activation. Case presentation We report the case of an 80-year-old Japanese woman with recurrent Takotsubo syndrome complicated with ischemic enteritis. In this case, abdominal pain and dehydration due to ischemic enteritis is thought to have triggered Takotsubo syndrome. Her life was saved with rapid, adequate intravenous hydration. She was diagnosed with coronary vasospastic angina using coronary angiography on her second admission. This case highlights the potential of adequate intravenous hydration in increasing coronary blood flow. In our case, it should be noted that pulmonary congestion was mild and may have improved Takotsubo syndrome without the use of diuretics. Conclusion Adequate hydration must be considered for prompt improvement of cardiac function in Takotsubo syndrome. Replenishment of fluid to increase coronary blood flow, improvement of heart load without exacerbating heart failure, and stabilization of circulation dynamics can help treat patients with Takotsubo syndrome without using diuretics.

389 Microvascular dysfunction in patients with Type II diabetes mellitus: invasive assessment of absolute coronary blood flow and microvascular resistance reserve

Aims Coronary microvascular dysfunction (CMD) is an early feature of diabetic cardiomyopathy, which usually precedes the onset of diastolic and systolic dysfunction. Continuous intracoronary thermodilution allows an accurate and reproducible assessment of absolute coronary blood flow and microvascular resistance thus allowing the evaluation of coronary flow reserve (CFR) and Microvascular Resistance Reserve (MRR), a novel index specific for microvascular function, which is independent from the myocardial mass. In the present study we compared absolute coronary flow and resistance, CFR and MRR assessed by continuous intracoronary thermodilution in diabetic vs. non-diabetic patients. Left atrial reservoir strain (LASr), an early marker of diastolic dysfunction was compared between the two groups. Methods In this observational retrospective study, 108 patients with suspected angina and non-obstructive coronary artery disease (NOCAD) consecutively undergoing elective coronary angiography (CAG) from September 2018 to June 2021 were enrolled. The invasive functional assessment of microvascular function was performed in the left anterior descending artery (LAD) with intracoronary continuous thermodilution. Patients were classified according to the presence of DM. Absolute resting and hyperaemic coronary blood flow (in mL/min) and resistance (in WU) were compared between the two cohorts. FFR was measured to assess coronary epicardial lesions, while CFR and MRR were calculated to assess microvascular function. LAS, assessed by speckle tracking echocardiography, was used to detect early myocardial structural changes potentially associated with microvascular dysfunction. Results The median FFR value was 0.83 (0.79–0.87) without any significant difference between the two groups. Absolute resting and hyperaemic flow in the left anterior descending coronary were similar between diabetic and non-diabetic patients. Similarly, resting and hyperaemic resistances did not change significantly between the two groups. In the DM cohort the CFR and MRR were significantly lower compared to the control group [CFR = 2.38 ± 0.61 and 2.88 ± 0.82; MRR = 2.79 ± 0.87 and 3.48 ± 1.02 for diabetic and non-diabetic patients respectively, (P < 0.05 for both)]. Likewise, diabetic patients had a significantly lower reservoir, contractile and conductive LAS (all P < 0.05). Conclusions Compared with non-diabetic patients, CFR and MRR were lower in patients with DM and non-obstructive epicardial coronary arteries, while both resting and hyperaemic coronary flow and resistance were similar. LASr was lower in diabetic patients, confirming the presence of a subclinical diastolic dysfunction associated to the microcirculatory impairment. Continuous intracoronary thermodilution-derived indexes provide a reliable and operator-independent assessment of coronary macro- and microvasculature and might potentially facilitate widespread clinical adoption of invasive physiologic assessment of suspected microvascular disease.

To Balloon or Not to Balloon? The Effects of an Intra-Aortic Balloon-Pump on Coronary Artery Flow during Extracorporeal Circulation Simulating Normal and Low Cardiac Output Syndromes

ECMO is the most frequently used mechanical support for patients suffering from low cardiac output syndrome. Combining IABP with ECMO is believed to increase coronary artery blood flow, decrease high afterload, and restore systemic pulsatile flow conditions. This study evaluates that combined effect on coronary artery flow during various load conditions using an in vitro circuit. In doing so, different clinical scenarios were simulated, such as normal cardiac output and moderate-to-severe heart failure. In the heart failure scenarios, we used peripheral ECMO support to compensate for the lowered cardiac output value and reach a default normal value. The increase in coronary blood flow using the combined IABP-ECMO setup was more noticeable in low heart rate conditions. At baseline, intermediate and severe LV failure levels, adding IABP increased coronary mean flow by 16%, 7.5%, and 3.4% (HR 60 bpm) and by 6%, 4.5%, and 2.5% (HR 100 bpm) respectively. Based on our in vitro study results, combining ECMO and IABP in a heart failure setup further improves coronary blood flow. This effect was more pronounced at a lower heart rate and decreased with heart failure, which might positively impact recovery from cardiac failure.

Coronary vasodilation mediated by T cells expressing choline acetyltransferase

This study shows ChAT-expressing T cells can induce vasodilation of the blood vessel in the coronary circulation and that this effect relies on a direct interaction between T cells and the coronary vascular endothelium. The study establishes a potential immunomodulatory role for T cells in the coronary circulation. The present findings offer an additional possibility that a deficiency of ChAT-expressing T cells could contribute to reduced coronary blood flow and ischemic events in the myocardium.