W. Martin

Radiofrequency ablation for persistent atrial fibrillation in patients with advanced heart failure and severe left ventricular systolic dysfunction: a randomised controlled trial

Objective To determine whether or not radiofrequency ablation (RFA) for persistent atrial fibrillation in patients with advanced heart failure leads to improvements in cardiac function. Setting Patients were recruited from heart failure outpatient clinics in Scotland. Design and intervention Patients with advanced heart failure and severe left ventricular dysfunction were randomised to RFA (rhythm control) or continued medical treatment (rate control). Patients were followed up for a minimum of 6 months. Main outcome measure Change in left ventricular ejection fraction (LVEF) measured by cardiovascular MRI. Results 22 patients were randomised to RFA and 19 to medical treatment. In the RFA group, 50% of patients were in sinus rhythm at the end of the study (compared with none in the medical treatment group). The increase in cardiovascular magnetic resonance (CMR) LVEF in the RFA group was 4.5±11.1% compared with 2.8±6.7% in the medical treatment group (p=0.6). The RFA group had a greater increase in radionuclide LVEF (a prespecified secondary end point) than patients in the medical treatment group (+8.2±12.0% vs +1.4±5.9%; p=0.032). RFA did not improve N-terminal pro-B-type natriuretic peptide, 6 min walk distance or quality of life. The rate of serious complications related to RFA was 15%. Conclusions RFA resulted in long-term restoration of sinus rhythm in only 50% of patients. RFA did not improve CMR LVEF compared with a strategy of rate control. RFA did improve radionuclide LVEF but did not improve other secondary outcomes and was associated with a significant rate of serious complications. Clinical trials registration number NCT00292162.

Quantitative gated SPECT: the effect of reconstruction filter on calculated left ventricular ejection fractions and volumes.

Gated SPECT (GSPECT) offers the possibility of obtaining additional functional information from perfusion studies, including calculation of left ventricular ejection fraction (LVEF). The calculation of LVEF relies upon the identification of the endocardial surface, which will be affected by the spatial resolution and statistical noise in the reconstructed images. The aim of this study was to compare LVEFs and ventricular volumes calculated from GSPECT using six reconstruction filters. GSPECT and radionuclide ventriculography (RNVG) were performed on 40 patients; filtered back projection was used to reconstruct the datasets with each filter. LVEFs and volumes were calculated using the Cedars-Sinai QGS package. The correlation coefficient between RNVG and GSPECT ranged from 0.81 to 0.86 with higher correlations for smoother filters. The narrowest prediction interval was 111 +/- 2%. There was a trend towards higher LVEF values with smoother filters, the ramp filter yielding LVEFs 2.55 +/- 3.10% (p < 0.001) lower than the Hann filter. There was an overall fall in ventricular volumes with smoother filters with a mean difference of 13.98 +/- 10.15 ml (p < 0.001) in EDV between the Butterworth-0.5 and Butterworth-0.3 filters. In conclusion, smoother reconstruction filters lead to lower volumes and higher ejection fractions with the QGS algorithm, with the Butterworth-0.4 filter giving the highest correlation with LVEFs from RNVG. Even if the optimal filter is chosen the uncertainty in the measured ejection fractions is still too great to be clinically acceptable.

Quantitative gated SPECT myocardial perfusion imaging with 201Tl: an assessment of the limitations

Gated SPECT (GSPECT) perfusion imaging has been increasing in popularity both with 99Tcm agents and 201Tl. However, both higher activities than administered in the UK and multi-headed cameras are often used. The aim of this study was to assess GSPECT imaging using lower activities of 201Tl with a single-headed camera. Seventy patients underwent stress and redistribution GSPECT imaging after a mean injected activity of 62±7 MBq 201Tl. These patients also underwent radionuclide ventriculography (RNVG) imaging. The Cedars Sinai Quantitative Gated SPECT (QGS) package was used to calculate left ventricular ejection fraction (LVEF) from the GSPECT studies. Comparison of ejection fractions calculated using GSPECT with those calculated using RNVG yielded a correlation coefficient of 0.70 for the stress studies and 0.71 for the redistribution studies. The width of the mean 95% prediction interval ranged from 22 to 74 percentage points for the stress studies and 22 to 86 percentage points for the redistribution studies. Ejection fractions calculated from stress and redistribution GSPECT studies showed a correlation of 0.80 with a mean 95% prediction interval of 42.6±0.4 percentage points. In conclusion, left ventricular ejection fractions calculated using the QGS algorithm from 201Tl GSPECT studies are inadequate for use in clinical practice.

Cardiovascular effects of prenalterol on rest and exercise haemodynamics in patients with chronic congestive cardiac failure.

?The cardiovascular effects of the cardioselective beta, agonist prenalterol have been studied in nine patients with severe chronic congestive cardiac failure and in six patients with left ventricular dysfunction resulting from previous myocardial infarction. In the patients with cardiac failure intravenous prenalterol in a dosage of 1.5 microgram/kg bodyweight increased the cardiac index from 1.8 +/- 0.1 to 21.+/- 0.1 1/min per m2 and the left ventricular ejection fraction from 22 +/- 3 to 28 +/- 3%. There was a modest but significant increase in heart rate from 76 +/- 3 to 87 +/- 4 beats/min. Systemic vascular resistance fell from 2285 +/- 51 to 2041 +/- 534 dynes s-1 cm-5. On exercise, the left ventricular filling pressure fell from 33 +/- 6 to 26 +/- 3 and both cardiac index and stroke index increased by 13% and 16%, respectively. There was no significant change in heart rate or systemic blood pressure. In the patients with left ventricular dysfunction, coronary sinus blood flow increased from 107 +/- 11 to 133 +/- 12 ml/min but the increase in myocardial oxygen consumption was small and not significant (11.6 +/- 1.2 and 14.5 +/- 1.9 ml/min). In all patients there was no evidence that prenalterol was arrhythmogenic.

Downscatter correction and choice of collimator in 123I imaging

(123)I imaging is increasingly used in nuclear medicine but downscatter from high (>300 keV) energy emissions degrades the image and introduces variation in sensitivity with depth when imaging with a low energy collimator. A dual windowing technique using a matched window immediately above the principle window to correct for the effects of downscatter is described. The technique is shown to correct for the variation in sensitivity with depth and to reduce outlying scatter. Quantitative imaging of (123)I using a low energy collimator should always employ downscatter correction.

Validation of an echocardiographic wall motion index in heart failure due to ischaemic heart disease.

the echocardiographic assessment of left ventricular ejection fraction (LVEF) by geometric methods is limited in many patients because of inadequate views and also in the presence of regional wall motion abnormalities due to ischaemic heart disease (IHD). This study aimed to examine the application of a wall motion index (WMI) method, using a nine‐segment LV model in patients with chronic heart failure (CHF) due to IHD.

I-123 MIBG cardiac uptake measurements: limitations of collimator choice and scatter correction in the clinical context.

ObjectiveLow uptake of metaiodobenzylguanidine (MIBG) in patients with heart failure generally indicates poor prognosis. Our objective was to determine the best method for calculating I-123 MIBG uptake. MIBG uptake as a percentage of the injected dose is presented as an alternative method for serial assessment. MethodsPatients with chronic heart failure were imaged with I-123 MIBG with both a medium-energy (ME) collimator and a low-energy high-sensitivity (LEHS) collimator. Scatter correction was used to correct the LEHS images. Heart-to-mediastinal (H/M) ratio and the percentage of myocardial uptake of MIBG were obtained. ResultsMean H/M ratios for the ME images, LEHS images and scatter-corrected LEHS images were 2.45±0.61, 2.22±0.47 and 2.51±0.62, respectively. Mean H/M ratio was significantly different among all the three sets (P<0.001) of images. The average difference in H/M ratios between the ME images and LEHS images was lower when scatter correction was applied (4.95% vs. 9.79%). The error in calculating the myocardial uptake as a percentage of the injected dose was significantly lower than the error in calculating H/M ratio (0.2 vs.10.2% LEHS; 0.3 vs.16.0% ME; 0.2 vs.11.8% LEHS scatter corrected). ConclusionFor quantitative assessment of H/M ratio in I-123 MIBG imaging a LEHS collimator can be used in place of a ME collimator to achieve better counting statistics, but scatter correction must be used. The calculation of the myocardial uptake as a percentage of the injected dose has potential as an alternative method of measurement, particularly for serial assessment.

Are ejection fractions from gated SPECT perfusion studies clinically useful? A comparison with radionuclide ventriculography

Gated SPECT (GSPECT) was evaluated for the measurement of left ventricular ejection fraction (LVEF) by comparing with equilibrium gated radionuclide ventriculography (RNVG). A total of 99 subjects underwent GSPECT and RNVG imaging. All studies were acquired in list mode with GSPECT studies processed to give 16- and 8-frames per R-R interval, and RNVG studies 24 frames per R-R interval. The Cedars-Sinai QGS software was used to calculate ejection fraction from GSPECT studies. RNVG studies were processed using a manually drawn single region of interest technique. Comparison of LVEF from GSPECT with RNVG yielded correlation coefficients of 0.82 and 0.81 for 16- and 8-frame GSPECT studies respectively. The mean 95% prediction interval was 33 +/- 11 percentage points for both 16- and 8-frame studies, indicating a great disparity between predicted ejection fraction values from GSPECT and actual RNVG values. Subgroup analysis of 29 patients with pathological Q-wave evidence of myocardial infarction demonstrated a poorer correlation coefficient of r = 0.69. Subgroup analysis of 32 patients with end-diastolic volumes < 100 ml demonstrated a poorer correlation coefficient of r = 0.32. Ejection fractions calculated from 16- and 8-frame studies showed a correlation of 0.99 with a mean 95% prediction interval of 8.7 +/- 0.04 percentage points. The 8-frame studies underestimated LVEF by 3.6 +/- 2.3% compared to the 16-frame studies. In conclusion, left ventricular ejection fractions calculated using the QGS algorithm from GSPECT studies are inadequate for use in clinical practice.

Laser profiling: a technique for the study of prosthetic heart valve leaflet motion.

A detailed understanding of the stresses and strains developed in functioning flexible-leaflet valves is necessary if a durable, non-thrombogenic heart valve replacement is to be realized. A new experimental tool, laser profiling, is presented for the study of flexible-leaflet heart valve dynamics. Profiles of moving leaflet surfaces are obtained by projecting parallel sheets of laser light onto valve leaflets as the valves open and close in a mock circulatory loop. Two versions of laser profiling have been developed. In two-dimensional mode multiple profiles are generated on a fixed plane in space but at discrete intervals in time, whereas in three-dimensional mode multiple profiles are generated across the leaflet surface at (effectively) a single instant in time. Highlighted leaflet profiles are captured by camera and transferred to an image processing system for analysis. A simple algorithm permits digitized profiles to be reconstructed within a computer-aided design software package, providing detailed visualization and quantification of valve motion. Extensive validation studies have been performed using the Medtronic-Hall mechanical prosthetic heart valve. Laser profiling enables computer reconstruction of the rigid occluder to an accuracy of +/- 200 microns from a 0.7 ms exposure taken during the period at which the occluder moves with greatest velocity. The technique has been applied to investigate the leaflet dynamics of a bovine pericardial heart valve prosthesis.

Exercise 201Tl/rest 99Tcm-tetrofosmin myocardial perfusion imaging : A convenient protocol for the assessment of coronary disease

Standard exercise thallium-201 (201Tl)-redistribution protocols for the detection of coronary artery disease take about 4 h to complete. This is inconvenient for both patients and staff. The higher energy technetium-99m (99Tcm) emissions permit immediate imaging after 201Tl with minimal crosstalk. This study assessed exercise gated planar 201Tl scintigraphy (55 MBq) followed by rest gated planar 99Tcm-tetrofosmin scintigraphy (250 MBq) in 32 patients. The results showed a high sensitivity for the detection of coronary disease (100%) in this highly selective group of patients. In order to diagnose myocardial infarction accurately, it was necessary to view the gated 201Tl images and assess regional wall motion in a defect zone. This gave a specificity of 88% and a sensitivity of 71% for the prediction of myocardial infarction on the angiographic ventriculogram. Stress 201Tl/rest 99Tcm-tetrofosmin is a useful short protocol for patients unable to complete the full 4-h exercise 201Tl-redistribution study.