3326Infective endocarditis after transcatheter aortic valve implantation: findings from a UK nationwide linkage study

Introduction

Infective endocarditis (IE) is a potentially fatal complication of prosthetic valve replacement and increasing use of transcatheter aortic valve implantation (TAVI) has resulted in a new elderly and frail population at increased risk of IE. The incidence of IE after TAVI and factors that influence the risk and subsequent outcome are relatively unknown.

Purpose

To describe the incidence, predictors, echocardiographic findings, microbiology and clinical outcomes of IE following TAVI in the United Kingdom (UK).

Methods

Patients who underwent TAVI between Jan 1 2007 and Dec 31 2016 were identified from the UK TAVI database held by the National Institute for Cardiovascular Outcomes Research. For this cohort, all hospital admissions with a primary diagnosis of IE were identified by linkage with the NHS Hospital Episode Statistics Admitted Patient Care database, or by contact with regional TAVI centres. Additional information concerning clinical presentation, imaging findings, microbiology, management and patient outcome were obtained where possible from the treating physician.

Results

A total of 16,014 patients underwent TAVI, of whom 157 developed IE over a median follow-up of 23.8 (IQR 7.8–52.4) months - an overall incidence of 0.98% (0.53% at one year post-TAVI). The mean age of patients with IE was 79.2±7.8 years, and 69% were male. The median time to IE following TAVI was 10.0 (IQR 4.0–22.3) months.

On multivariate analysis, IE was significantly more common in men (HR 2.05, 95% CI 1.35–3.11, p=0.001) and in patients receiving mechanically-expandable (HR 2.15, 95% CI 1.16–4.01, p=0.015) or balloon-expandable valves (HR 1.60, 95% CI 1.01–2.52, p=0.045) compared to self-expanding valves. IE was also more common in those with an aortic valve peak gradient following TAVI deployment greater than median (HR 1.81, 95% CI 1.23–2.67, p=0.003).

The most common presenting symptom was fever (present in 67.1%). The most frequent causal organisms were enterococci (25.9%), followed by oral streptococci (16.4%) and Staphylococcus aureus (11.8%). Transoesophageal echocardiography demonstrated vegetations in 72.5% of patients, most commonly on the TAVI valve leaflets (58.8%). Only 8.24% of patients underwent surgical valve intervention.

Survival rates at hospital discharge and one year follow up were 61.4% and 54.4%, respectively. Specific factors associated with one-year mortality were cardiogenic shock (HR 4.6, 95% CI 2.1–10.3, p=0.0002), septic shock (HR 3.4, 95% CI 1.4–8.3, p=0.006) and stroke (HR 4.9, 95% CI 1.46–16.7, p=0.01).

Conclusions

The incidence of IE one year after TAVI was 0.53% and greater risk was associated with male sex, mechanically-expandable and balloon-expandable valves, and elevated post-deployment valve gradient. Enterococci were the most common causative organism. Overall survival at one year was 54.4%, with adverse outcome predicted by cardiogenic shock, septic shock or stroke.

Occlusion of internal mammary grafts: a review of the potential causative factors

The outcome of patient undergoing CABG is largely dependant on the long-term patency of the conduit used. Internal mammary artery (IMA) is considered whenever possible due to its improved long-term functionality over saphenous vein graft. However, a 10% rate of late arterial closure is described without well-known predictors. Chronic competition induced by a moderate coronary lesion on the bypassed native vessel is thought to be a major factor of arterial graft shrinkage even if conflicting data are reported in the available literature. Therefore, the decision to use an IMA to bypass a moderate native coronary lesion should be carefully weighted. When angiography is doubtful, more accurate functional investigations should be considered. Among them, pressure-derived fractional flow reserve could give an immediate answer of whether an intermediate lesion should be bypassed.

Impaired endothelial regulation of ventricular relaxation in cardiac hypertrophy: role of reactive oxygen species and NADPH oxidase

BACKGROUND

Endothelium-derived nitric oxide (NO) selectively enhances myocardial relaxation. In experimental left ventricular hypertrophy (LVH), this endothelium-dependent LV relaxant response is impaired despite a preserved response to exogenous NO. We investigated the potential role of reactive oxygen species (ROS) in this defect.

METHODS AND RESULTS

Short-term treatment with the antioxidants vitamin C (10 micromol/L) or deferoxamine (500 micromol/L) restored LV relaxant responses to the NO agonists bradykinin (10 nmol/L) and substance P (100 nmol/L) in isolated ejecting hearts of aortic-banded guinea pigs. Substance P decreased the time to onset of LV relaxation (tdP/dt(min)) by -6.8+/-1.7 ms in the presence of vitamin C and by -8.9+/-2.2 ms in the presence of deferoxamine compared with -0.8+/-2.2 ms in the absence of antioxidants (P<0.05 either antioxidant versus control). A similar restoration of relaxant response to substance P was observed in the presence of the superoxide dismutase mimetic, Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride (10 micromol/L), but not with tetrahydrobiopterin or L-arginine. Protein expression of the NADPH oxidase subunits gp91-phox and p67-phox and myocardial NADPH oxidase activity were significantly increased (P<0.05) in the banded group compared with shams.

CONCLUSIONS

An increase in ROS, most likely derived at least in part from NADPH oxidase, is responsible for the impaired endothelial regulation of LV relaxation in LVH. These are the first data to potentially link increased NADPH oxidase-derived ROS with a defect in cardiac contractile function in a pathological setting.

Effects of nitric oxide synthase inhibition on Basal function and the force-frequency relationship in the normal and failing human heart in vivo

BACKGROUND

Nitric oxide (NO) exerts autocrine/paracrine effects on cardiac function, including alterations of the inotropic state. In vitro studies suggest that NO modulates the myocardial force-frequency relationship. Basal left ventricular (LV) contractility is depressed and the force-frequency relationship is blunted in human heart failure, and it is speculated that an increase in NO production is involved.

METHODS AND RESULTS

We compared the effects of intracoronary NO synthase inhibition with N(G)-monomethyl-L-arginine (L-NMMA; 25 micromol/min) on basal LV function and the response to incremental atrial pacing in patients with dilated cardiomyopathy (n=11; mean age, 51 years) and in control subjects with atypical chest pain and normal cardiac function (n=7; mean age, 54 years). In controls, L-NMMA significantly reduced basal LV dP/dt(max) (from 1826 to 1578 mm Hg/s; P<0.002), but had no effect on heart rate, mean aortic pressure, or right atrial pressure. Pacing-induced increases in LV dP/dt(max) were unaltered by L-NMMA. In patients with dilated cardiomyopathy, L-NMMA had no effect on baseline LV dP/dt(max) (from 1313 to 1337 mm Hg/s; P=NS). The blunted pacing-induced rise in LV dP/dt(max) in these patients was unaltered by L-NMMA.

CONCLUSION

Endogenous NO has a small baseline positive inotropic effect in the normal human heart, which is lost in heart failure patients. NO does not significantly influence the force-frequency relationship in either the normal or failing human heart in vivo. Because this study was performed in patients with moderate heart failure, whether the findings apply to subjects with more severe heart failure requires further investigation.

Divergent biological actions of coronary endothelial nitric oxide during progression of cardiac hypertrophy

Coronary endothelial NO synthase expression and NO bioactivity were investigated at sequential stages during the progression of left ventricular hypertrophy. Male guinea pigs underwent abdominal aortic banding or sham operation. Left ventricular contractile function was quantified in isolated ejecting hearts. Coronary endothelial and vasodilator function were assessed in isolated isovolumic hearts in response to boluses of bradykinin (0.001 to 10 micromol/L), substance P (0.01 to 100 micromol/L), diethylamine NONOate (DEA-NO) (0.1 to 1000 micromol/L), N(G)-monomethyl-L-arginine monoacetate (L-NMMA) (10 mmol/L), and adenosine (10 mmol/L). At a stage of compensated left ventricular hypertrophy (3 weeks), left ventricular endothelial NO synthase protein expression was unaltered (Western blot and immunocytochemistry). Vasoconstriction in response to L-NMMA was increased in banded animals compared with sham-operated animals (13.8+/-2.1% versus 6.2+/-1.3%, n=10; P<0.05), but agonist- and DEA-NO-induced vasodilation was similar in the 2 groups. At a stage of decompensated left ventricular hypertrophy (8 to 10 weeks), left ventricular endothelial NO synthase protein expression was significantly lower in banded animals (on Western analysis: banded animals, 7.8+/-0.4 densitometric units; sham-operated animals, 12.2+/-1.7 densitometric units; n=5; P<0.05). At this time point, vasoconstriction in response to L-NMMA was similar in the 2 groups, but vasodilatation in response to bradykinin (30.9+/-2.4% versus 39.7+/-2.2%, n=10; P<0.05), DEA-NO (26.2+/-1.8% versus 34.6+/-1.8%, n=10; P<0.05), and adenosine (24.3+/-2.0% versus 35.7+/-2.0%, n=10; P<0.01) was attenuated in banded animals. These findings indicate that there is an increase in the basal activity of NO (without a significant change in endothelial NO synthase expression) in early compensated left ventricular hypertrophy, followed by a decrease in both endothelial NO synthase expression and NO bioactivity during the transition to myocardial failure.

The physiological role of endogenous endothelin in the regulation of human coronary vasomotor tone

OBJECTIVES

The study was done to investigate the physiological role of endogenous endothelin-1 in the human coronary circulation by studying the effect of an intracoronary infusion of the specific endothelin receptor subtype A (ETA) receptor antagonist BQ123 on coronary vasomotor tone.

BACKGROUND

Endothelin-1 contributes to the maintenance of peripheral vascular tone in humans. However, its physiological role in the human coronary vasculature is unknown.

METHODS

We studied 12 patients (mean age 54.7 +/- 2.5 years, 3 men) undergoing cardiac catheterization for investigation of atypical chest pain, with angiographically normal coronary arteries. Coronary artery cross-sectional area was measured with digital quantitative coronary angiography, and coronary blood flow was assessed with an intracoronary Doppler flow wire. Flow-mediated (adenosine, 18 microg) and agonist-mediated (substance P, 20 pmol/min for 2 min) endothelial responses were measured prior to study. BQ123 (40 nmol/min for 15 min and monitored for a further 15 min) was infused into the left coronary artery.

RESULTS

The BQ123 caused significant dilation of the proximal (artery cross-sectional area: 8.08 +/- 0.9 to 8.88 +/- 0.9 mm2; p < 0.05), mid (5.32 +/- 0.8 to 6.49 +/- 0.8 mm2; p < 0.001) and distal study vessel (2.11 +/- 0.2 to 2.50 +/- 0.2 mm2; p < 0.05). There was an increase in coronary blood flow (26.8 +/- 2.8 to 32.8 +/- 3.4 ml/min; p < 0.001) but no change in systemic hemodynamics. Baseline flow- or substance P-induced epicardial vasodilation did not correlate with the degree of vasodilation induced by BQ123.

CONCLUSIONS

These data uncover a role of endogenous endothelin-1 in the maintenance of basal vasomotor tone in patients with angiographically normal coronary arteries.

Impaired endothelium-dependent regulation of ventricular relaxation in pressure-overload cardiac hypertrophy

BACKGROUND

Endothelium-derived nitric oxide (NO) selectively enhances myocardial relaxation and may benefit diastolic function. Left ventricular hypertrophy (LVH) is characterized by abnormal myocardial relaxation and endothelial dysfunction. We investigated endothelium-dependent regulation of LV relaxation in moderate pressure-overload LVH induced by aortic banding in guinea pigs.

METHODS AND RESULTS

Isolated ejecting hearts of banded or sham-operated animals (shams) were studied. The specific agonists for endothelial release of NO, bradykinin (10 nmol/L), and substance P (100 nmol/L) both induced earlier onset of LV relaxation in shams (time to LV dP/dt(min) [tdP/dt(min)], -13.4+/-3.0 and -10.4+/-2.5 ms, respectively) without altering peak LV pressure or LV dP/dt(max). Neither agent altered tdP/dt(min) in banded animals. The ACE inhibitor captopril (1 micromol/L) also selectively reduced tdP/dt(min) in shams via a bradykinin/NO-dependent mechanism but had no effect in banded animals. An exogenous NO donor, sodium nitroprusside (0.1 micromol/L), selectively reduced tdP/dt(min) to a similar extent in both shams and banded animals. Endothelial-type NO synthase (eNOS) protein expression in whole LV homogenate was unaltered in banded animals.

CONCLUSIONS

Endothelium-dependent enhancement of LV relaxation is impaired in moderate pressure-overload LVH, despite a preserved response to exogenous NO. This is not accounted for by altered eNOS expression. These abnormalities may contribute to diastolic dysfunction in LVH.

Paracrine and autocrine effects of nitric oxide on myocardial function

Complex paracrine interactions exist between endothelial cells and cardiac myocytes in the heart. Cardiac endothelial cells release (or metabolize) several diffusible agents (e.g., nitric oxide [NO], endothelin-1, angiotensin II, adenylpurines) that exert direct effects on myocyte function, independent of changes in coronary flow. Some of these mediators are also generated by cardiac myocytes, often under pathological conditions. This review focuses on the role of NO in this paracrine/autocrine pathway. NO modulates several aspects of "physiological" myocardial function (e.g., excitation-contraction coupling; myocardial relaxation; diastolic function; the Frank-Starling response; heart rate; beta-adrenergic inotropic response; and myocardial energetics and substrate metabolism). The effects of NO are influenced by its cellular and enzymatic source, the amount generated, the presence of reactive oxygen species, interactions with neurohumoral and other stimuli, and the relative activation of cyclic GMP-dependent and -independent signal transduction pathways. The relative physiological importance of endothelium- and myocyte-derived NO remains to be established. In pathological situations (e.g., ischemia-reperfusion, left ventricular hypertrophy, heart failure, transplant vasculopathy and rejection, myocarditis), NO can potentially exert beneficial or deleterious effects. Beneficial effects of NO can result from endothelial-type nitric oxide synthase-derived NO or from spatially and temporally restricted expression of the inducible isoform, inducible-type nitric oxide synthase. Deleterious effects may result from (1) deficiency of NO or (2) excessive production, often inducible-type nitric oxide synthase-derived and usually with concurrent reactive oxygen species production and peroxynitrite formation. The balance between beneficial and deleterious effects of NO is of key importance with respect to its pathophysiological role.

Contrasting inotropic effects of endogenous endothelin in the normal and failing human heart: studies with an intracoronary ET(A) receptor antagonist

BACKGROUND

Endothelin-1 (ET-1) is a potent positive inotrope in vitro, but its physiological effects on intrinsic myocardial contractile function in humans in vivo are unknown. Plasma ET-1 levels are elevated in heart failure, and ET-1 may be involved in the pathophysiology of this condition. However, its effects on contractile function of the failing human heart are also unknown.

METHODS AND RESULTS

A specific ET(A) receptor antagonist, BQ123, was infused (40 nmol/min, 16 minutes) into the left coronary artery in 8 patients with atypical chest pain (normal left ventricular ¿LV function and coronary arteries) and 8 patients with nonischemic dilated cardiomyopathy (DCM) who were undergoing diagnostic catheterization. In normal subjects, BQ123 rapidly induced a significant reduction in LV dP/dt(max) (-270+/-71 mm Hg/s after 16 minutes; P<0.05) and in LV dP/dt at a developed pressure of 40 mm Hg (LV dP/dt(40)) (-179+/-54 mm Hg/s; P<0.05). In DCM patients, however, BQ123 caused no reductions in LV dP/dt(max) (62+/-49 mm Hg/s after 16 minutes) or LV dP/dt(40) (83+/-51 mm Hg/s;P<0.05 compared with normal subjects). BQ123 had no effect on heart rate, LV relaxation, LV end-diastolic pressure, right atrial pressure, or pulmonary pressure in either patient group.

CONCLUSIONS

Endogenous ET-1 has a tonic positive inotropic effect in normal subjects, independent of effects on the peripheral vasculature and unmasked by inhibition of ET(A) receptors. However, the effect of short-term ET(A) blockade in DCM patients was opposite to that in normal subjects, which suggests that ET-1 may cause negative inotropic effects in the failing heart.

ATP is involved in myocardial and vascular effects of exogenous bradykinin in ejecting guinea pig heart

It has recently been reported that bradykinin induces selective left ventricular (LV) relaxation in isolated guinea pig hearts via the release of nitric oxide. Exogenous bradykinin also induces vasodilation, which is only partly due to nitric oxide release. In the present study we investigated the role of adenyl purines on these bradykinin-induced effects. Isolated ejecting guinea pig hearts were studied. LV pressure was monitored by a 2-Fr micromanometer-tipped catheter. ATP concentrations were measured using a luciferin-luciferase assay. Bradykinin (1 and 100 nM) caused a progressive acceleration of LV relaxation together with a transient increase in coronary flow. These effects were inhibited by the nonselective P(2) purinoceptor antagonist suramin (1 microM, n = 6) but were unaffected by the selective P(2x) purinoceptor antagonist pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid (1 microM, n = 6). These myocardial and vascular effects of bradykinin were associated with increased ATP levels in coronary effluent. These data suggest that the selective enhancement of LV relaxation and rise in coronary flow induced by exogenous bradykinin involve endogenous ATP and the subsequent stimulation of P(2) purinoceptors.

Prospective randomized trial of single clamp technique versus intermittent ischaemic arrest: myocardial and neurological outcome

OBJECTIVE

To explore the hypothesis that intermittent ischaemic arrest (IIA) provides better myocardial preservation but generates a larger number of cerebral microemboli (ME) and consequently a higher incidence of post-operative cerebral dysfunction compared with the single clamp technique (SCT).

METHODS

Ninety-one patients with stable angina undergoing elective CABG with no clinical evidence of aortic or cerebro-vascular or neurological disease were prospectively randomized to: IIA (n = 43) or SCT with intermittent anterograde cold blood cardioplegia (n = 48). Myocardial preservation was assessed by measuring serum CK-MB, Troponin-T (TnT) and Troponin-I (TnI) and from pre- and post-operative ECGs and left ventricular (LV) function by echocardiography. Intra-operative cerebral ME were counted by transcranial Doppler of the right middle cerebral artery. All patients completed the Luria Nebraska Neuropsychological Battery (LNNB) tests for motor, visual, reading, memory and intellectual processes the day before surgery and at 1 week and 6 months post-operatively. Serum levels of the neuro-specific protein S-100 were measured.

RESULTS

The two groups were comparable for age, sex, extent of coronary disease, previous myocardial infarction, diabetes, hypertension and number of arterial and venous grafts. The median number of ME detected per patient was 34 (range 4-208) and was similar in both groups. Protein S-100 levels remained normal and similar in both groups at all times except in one patient with SCT who had an operative stroke. LNNB scores were similarly depressed at 1 week and recovered in all cases at 6 months. There was no correlation between the number of ME and LNNB scores. Median peak TnI levels were 0.64 microg/l with IIA vs. 0.87 microg/l with SCT (P = NS) and TnT 0.8 microg/l vs. 1.08 microg/l (P < 0.03). SCT was however associated with longer mean ischaemic (67.6 +/- 16.1 vs. 34.5 +/- 16.5 min, P < 0.001) and mean bypass time (88.5 +/- 18.2 vs. 74.6 +/- 26.3 min, P < 0.004) than IIA. Four patients with SCT and none with IIA had ECG changes suggestive of MI (P = 0.04).

CONCLUSION

During elective CABG in patients with no clinical evidence of aortic or cerebro-vascular disease the incidence of peri-operative ME and post-operative neuropsychological disturbances are comparable with both techniques of myocardial preservation. Biochemical analysis suggests that IIA provides more effective myocardial preservation.