Kim Greaves

Clinical criteria and the appropriate use of transthoracic echocardiography for the exclusion of infective endocarditis

Background: Clinical guidelines currently suggest that transthoracic echocardiography (TTE) be carried out in all patients with suspected endocarditis, but the use of TTE where there is a low probability of infective endocarditis has a poor diagnostic yield. This screening approach may no longer be appropriate. Objective: To examine whether clinical criteria might aid decision making with respect to the use of TTE in possible endocarditis. Design: A retrospective review of patient records. Setting: Cardiology department of a tertiary referral centre. Patients: 500 consecutive hospital inpatients referred for TTE to exclude endocarditis. Main outcome measures: Evidence of endocardial vegetations on TTE and the presence of predetermined clinical criteria that may predispose to, or be suggestive of, endocarditis. Results: Evidence of infective endocarditis was detected on echocardiography in 43 of the 500 patients (8.6%). In 239 patients (48%), vegetations and certain prespecified clinical criteria were both absent. These criteria were: vasculitic/embolic phenomena; the presence of central venous access; a recent history of injected drug use; presence of a prosthetic valve; and positive blood cultures. The collective absence of these five criteria indicated a zero probability of TTE showing evidence of endocarditis. Conclusions: The use of simple clinical criteria during the decision making process may avoid many unnecessary TTE examinations in hospital inpatients with a low probability of endocarditis.

Usefulness of myocardial contrast echocardiography using low-power continuous imaging early after acute myocardial infarction to predict late functional left ventricular recovery.

Microvascular perfusion is a prerequisite for ensuring viability early after acute myocardial infarction (AMI). For adequate assessment of myocardial perfusion, both myocardial blood volume and velocity need to be evaluated. Due to its high frame rate, low-power continuous myocardial contrast echocardiography (MCE) can rapidly assess these parameters of myocardial perfusion. We hypothesized that the technique can accurately differentiate necrotic from viable myocardium after reperfusion therapy in AMI. Accordingly, 50 patients underwent low-power continuous MCE using intravenous Optison (Amersham Health, Amersham, Middlesex, United Kingdom) 7 to 10 days after AMI. Myocardial perfusion (contrast opacification assessed over 15 cardiac cycles after the destruction of microbubbles with high energy pulses) and wall thickening were assessed at baseline. Regional and global left ventricular (LV) function was reassessed after 12 weeks. Out of the 297 dysfunctional segments, MCE detected no contrast enhancement during 15 cardiac cycles in 172 segments, of which 160 (93%) failed to show improvement. MCE demonstrated contrast opacification during 15 cardiac cycles in 77 segments, of which 65 (84%) showed recovery of function. The greater the extent and intensity of contrast opacification, the better the LV function at 3 months (p <0.001, r = -0.91). Almost all patients (94%) with <20% perfusion in dysfunctional myocardium (assessing various cut-offs) failed to demonstrate an improvement in LV function. MCE and peak creatine kinase proved to be independent predictors of functional recovery (p <0.001). In conclusion, low-power continuous MCE is an accurate and rapid bedside technique to identify microvascular perfusion after AMI. This technique may be utilized to reliably predict late recovery of function in dysfunctional myocardium after AMI.

Acute Hypoglycemia Decreases Myocardial Blood Flow Reserve in Patients With Type 1 Diabetes Mellitus and in Healthy Humans

Background— Hypoglycemia is associated with increased cardiovascular mortality, but the reason for this association is poorly understood. We tested the hypothesis that the myocardial blood flow reserve (MBFR) is decreased during hypoglycemia using myocardial contrast echocardiography in patients with type 1 diabetes mellitus (DM) and in healthy control subjects. Methods and Results— Twenty-eight volunteers with DM and 19 control subjects underwent hyperinsulinemic clamps with maintained sequential hyperinsulinemic euglycemia (plasma glucose, 90 mg/dL [5.0 mmol/L]) followed by hyperinsulinemic hypoglycemia (plasma glucose, 50 mg/dL [2.8 mmol/L]) for 60 minutes each. Low-power real-time myocardial contrast echocardiography was performed with flash impulse imaging using low-dose dipyridamole stress at baseline and during hyperinsulinemic euglycemia and hyperinsulinemic hypoglycemia. In control subjects, MBFR increased during hyperinsulinemic euglycemia by 0.57 U (22%) above baseline (B coefficient, 0.57; 95% confidence interval, 0.38 to 0.75; P<0.0001) and decreased during hyperinsulinemic hypoglycemia by 0.36 U (14%) below baseline values (B coefficient, −0.36; 95% confidence interval, −0.50 to −0.23; P<0.0001). Although MBFR was lower in patients with DM at baseline by 0.37 U (14%; B coefficient, −0.37; 95% confidence interval, −0.55 to −0.19; P=0.0002) compared with control subjects at baseline, the subsequent changes in MBFR during hyperinsulinemic euglycemia and hyperinsulinemic hypoglycemia in DM patients were similar to that observed in control subjects. Finally, the presence of microvascular complications in the patients with DM was associated with a reduction in MBFR of 0.52 U (24%; B coefficient, −0.52; 95% confidence interval, −0.70 to −0.34; P<0.0001). Conclusions— Hypoglycemia decreases MBFR in both healthy humans and patients with DM. This finding may explain the association between hypoglycemia and increased cardiovascular mortality in susceptible individuals.

Cardiac troponin T does not increase after electrical cardioversion for atrial fibrillation or atrial flutter

Objective To determine whether cardiac troponin T increases after electrical cardioversion in patients with atrial fibrillation or atrial flutter. Design Serum creatine kinase (CK), creatine kinase-MB (CKMB), and cardiac troponin T were measured before, 24 hours, and 48 hours after cardioversion in 15 patients with atrial fibrillation or atrial flutter. Results 12 of the 15 patients (80%) were successfully cardioverted to sinus rhythm. The median number of shocks was three (range one to six), the median cumulative energy 710u2009J (50 to 1430u2009J), and the median peak energy 300u2009J (50 to 360u2009J). Total CK increased from a baseline median concentration of 92 (45 to 259) to 1324 (96 to 6660) U/l at 24 hours and 1529 (120 to 4774) U/l at 48 hours after cardioversion. There was a small increase in CKMB but the ratio of CKMB to CK did not increase. There was no increase in cardiac troponin T in any patient. Conclusions Following electrical cardioversion of atrial fibrillation or atrial flutter, cardiac troponin T remains unchanged despite a large rise in total CK, indicating that the CK is derived from skeletal muscle and that myocardial injury does not occur. If cardiac troponin T is increased after cardioversion for atrial arrhythmias then other causes of myocardial damage should be sought.

Intensive glucose control and hypoglycaemia: a new cardiovascular risk factor?

Intensive glucose control is widely practiced in patients with diabetes mellitus and patients acutely admitted to hospitals with concomitant stress-induced hyperglycaemia. Such a strategy increases the risk of hypoglycaemia by several-fold. Hypoglycaemia leads to a surge in catecholamine levels with a profound haemodynamic response. In patients with a decreased cardiac reserve, such significant changes can culminate in serious or even fatal cardiovascular outcomes. This review is aimed at discussing in depth the evidence to date that links hypoglycaemia with cardiovascular mortality, reviewing the likely mechanisms underlying this association, as well as summarising these from a cardiologists perspective.

Myocardial perfusion echocardiography: a novel use in the diagnosis of sepsis-induced left ventricular systolic impairment on the intensive care unit

Impaired left ventricular systolic function secondary to sepsis can occur in up to 20% of patients with septic shock. The electrocardiogram (ECG) and echocardiographic changes it produces can be very similar to those occurring during acute coronary syndromes (ACS). Myocardial contrast echocardiography (MCE) allows assessment of myocardial perfusion. This technique can be performed at the bedside of the critically unwell patient. We describe a patient presenting with septic shock secondary to pneumonia. While sedated and ventilated in the intensive care unit, the patient developed marked ECG changes, a troponin rise and widespread left ventricular wall motion abnormality. The clinical picture suggested ACS or stress cardiomyopathy was unlikely and was more in keeping with a diagnosis of sepsis-induced left ventricular systolic dysfunction. To support this, resting and flash impulse MCE was performed which revealed normal perfusion in areas of both normal and abnormal wall motion. This suggested that the cardiac presentation was more likely to be due to left ventricular impairment secondary to sepsis and ACS therapy was discontinued. Pre-discharge ECG and transthoracic echocardiogram were normal. Percutaneous coronary angiography 6 weeks later was also normal. This is the first described case of MCE being used to aid in the decision-making process in distinguishing between ACS, stress cardiomyopathy, and left ventricular systolic impairment secondary to sepsis.

External Validation of the Manchester Acute Coronary Syndromes Decision Rule

OBJECTIVESnThe Manchester Acute Coronary Syndromes (MACS) decision rule has been shown to be a powerful diagnostic tool in emergency department (ED) patients with suspected acute coronary syndromes (ACS). It has the potential to improve system efficiency by identifying patients suitable for discharge after a single blood draw for high-sensitivity troponin and heart-type fatty acid-binding protein (h-FABP) analysis at presentation to the ED. The objective was to externally validate the MACS decision rule and establish its diagnostic accuracy as a discharge tool in a new set of prospectively recruited ED patients.nnnMETHODSnIn this preplanned analysis of a prospectively recruited single-center cohort, consecutive ED patients ≥18 years with suspected ACS were included. Testing for h-FABP and high-sensitivity troponin T was undertaken on serum drawn on arrival, and any clinical features required to calculate the MACS rule were recorded. The primary outcome was major adverse cardiac events (MACE) within 30 days (acute myocardial infarction [AMI], death, or revascularization). The secondary outcome was AMI alone, adjudicated using 6-hour troponin results.nnnRESULTSnOf the 782 participants included, 78 (10.0%) developed MACE and 61 (7.8%) had an AMI. Of participants, 133 (17.0%) were identified as very low risk and therefore suitable for immediate discharge with a 0% incidence of MACE or AMI. Of remaining patients, 314 (40.2%) were low risk, 320 (40.9%) were moderate risk, and 15 (1.9%) were high risk, with incidences of MACE of 2.2, 19.7, and 53.3%, respectively. The sensitivity was 100% (95% confidence interval [CI] = 95.4% to 100%) for MACE at 30 days and 100% (95% CI = 94.1% to 100%) for AMI. The area under the receiver operating characteristic curve was 0.87 (95% CI = 0.83 to 0.91) for the MACS rule in the prediction of MACE.nnnCONCLUSIONSnIn this prospectively recruited cohort of ED patients with suspected ACS, the MACS decision rule identifies a significant proportion of patients who are suitable for immediate discharge after a single blood draw at presentation, with a very low risk of MACE at 30 days. This study externally validates previous findings that the MACS rule is a powerful diagnostic tool in this setting. A randomized controlled trial to establish the utility of the rule in an everyday clinical setting is justified.

Stress echocardiography in the district hospital setting: a cost-saving analysis

AIMSnAccurate and cost-effective techniques are required for investigating patients experiencing chest pain, given the significant workload this patient cohort represents. We determined the cost impact of stress echocardiography compared with myocardial perfusion scintigraphy and coronary angiography in the investigation of patients with chest pain deemed unsuitable for exercise treadmill testing.nnnMETHODS AND RESULTSnA total of 200 patients with chest pain-with a low-intermediate probability of coronary artery disease-consecutively referred for stress echocardiography were recruited. Referring clinicians were asked which management strategy they would have chosen were the stress echocardiography service unavailable. The cost saving of stress echocardiography, an accuracy analysis, and adverse outcomes at 6 and 24 months follow-up were determined. The total cost attributable to the stress echocardiography service was Pound Sterling 58 368. If unavailable, 78 (39%) patients would have been referred for angiography and 122 (61%) for perfusion scintigraphy at a cost of Pound Sterling 56 316 and Pound Sterling 42 090, respectively, with a total cost of Pound Sterling 98 406. This represents a cost saving of Pound Sterling 40 038.nnnCONCLUSIONnStress echocardiography is a cost saving method for the investigation of chest pain in patients with low-intermediate risk of flow limiting coronary artery disease in the district hospital setting.

The Effects of Prolonged Acute Hypobaric Hypoxia on Novel Measures of Biventricular Performance

There are limited data on the effects of prolonged acute hypoxia on individual and global measures of biventricular function.

Relationship between myocardial perfusion with myocardial contrast echocardiography and function early after acute myocardial infarction for the prediction of late recovery of function

BACKGROUNDnFollowing ST elevation acute myocardial infarction (STEMI) and reperfusion therapy, there are often persistent wall thickening (WT) abnormalities and perfusion defects due to variable degree of myocardial stunning and necrosis. We hypothesised that following STEMI and reperfusion therapy, the extent of residual perfusion assessed by myocardial contrast echocardiography (MCE) and not the extent of WT abnormalities would predict subsequent global recovery of left ventricular (LV) function.nnnMETHODSnAccordingly, 112 patients with STEMI underwent simultaneous assessment of WT abnormality and perfusion using MCE 7+/-2 days after AMI and reperfusion therapy. Both WT and perfusion were scored on a 16 segment LV model. Contrast perfusion index (CPI), and global LV function were calculated. Echocardiography was repeated 12 weeks after reperfusion to assess recovery of LV function.nnnRESULTSnOf the 112 patients recruited, follow up echocardiography 12 weeks after reperfusion was available in 98 patients. CPI was significantly higher (p<0.0001) in the 66 patients, who showed late recovery of LV function (1.67+/-0.27) compared to those who did not show recovery of function (1.25+/-0.04). No significant difference was noted in the indices of baseline LV function in patients with (1.67+/-0.32) and without (1.80+/-0.36) recovery of LV function. The multivariable predictors of late recovery of function were MCE (p=0.02), absence of diabetes (p=0.02) and lower peak creatine kinase (p=0.01).nnnCONCLUSIONnThe extent of residual contrast perfusion and not WT abnormalities predicts late recovery of global LV function after acute myocardial infarction and reperfusion therapy.