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Torsten Toftegaard Nielsen

Publications and source records attributed to Torsten Toftegaard Nielsen.

50 records · Page 3Linked to original sources
PubMed2003

Electrocardiographic gated (99m)Tc-sestamibi SPECT immediately after primary percutaneous coronary intervention characterizes reperfusion success.

Following an acute myocardial infarction, the size of the infarct and the resulting left ventricular volume and function are important predictors of mortality. Identifying patients with impaired tissue level perfusion after percutaneous coronary intervention (PCI) for myocardial infarction therefore could have prognostic implications. To obtain combined measures of left ventricular perfusion, volumes and function we applied a gated myocardial perfusion imaging by (99m)Tc-sestamibi single photon emission computerized tomography to 19 patients immediately after revascularization by PCI and repeated this after 3 months. The results of the acute myocardial perfusion imaging significantly correlated to final infarct size, left ventricular volumes and function 3 months later. It is concluded that the method holds the potential for risk stratifying patients immediately after revascularization for acute myocardial infarction.

Aged↗
PubMed2003

Effects of L-glutamate supplementation mimic effects of fasting in the ischemic heart.

Endogenous glycogen stores are essential to maintain cell functions during myocardial ischemia.. Fasting and L-glutamate improve left ventricular function after an ischemic episode. We studied their effects on myocardial glycogen depletion during ischemia and on left ventricular function and glycogen resynthesis during reperfusion. We allocated 185 Wistar rats to 4 groups: 1) Control, 2) Fasting, 16-20 hours (Fast) 3) L-glutamate supplementation [100 mM] (Glt) or 4) Fasting + L-glutamate supplementation [100 mM]. n = 8-10 in each group. Hearts were mounted in an isolated perfused rat hearts model for 20 min stabilisation, 10/20/30 min ischemia and 60 min reperfusion. At each time point hearts were frozen in liquid nitrogen (-196 degrees C) within 2 seconds and myocardial contents of glycogen, lactate, alanine and glutamate were determined. Left ventricular pressure was measured continuously. Fasting and L-glutamate supplementation improved LV function after ischemia (Fast: p < 0.05, Glt: p < 0.01) and delayed myocardial glycogen depletion (Fast: p < 0.05, Glt: p < 0.01) compared to control. Decreased lactate accumulation and increased alanine content during ischemia were found in fasted (lactate: p < 0.05, alanine: p < 0.05) and L-glutamate supplemented (lactate: p < 0.01, alanine: p < 0.01) hearts compared to control. We did not find any additive effects of fasting and L-glutamate supplementation. In conclusion fasting and L-glutamate supplementation improve left ventricular function during reperfusion and delay myocardial glycogen depletion during ischemia. There were no additive effects of Fasting and L-glutamate supplementation. These finding suggest common metabolic pathways underlying the effects of L-glutamate supplementation and fasting.

Animals↗
PubMed2003

Ischaemic preconditioning in the pig assessed by myocardial perfusion imaging and histochemistry.

Ischaemic preconditioning (IP) is a strong endogenous infarct reducing stimulus which has not previously been evaluated with myocardial perfusion imaging using 99mTc-MIBI. Factors responsible for cellular MIBI uptake are affected by both IP and acute ischaemia (plasma membrane and mitochondrial membrane potential and oxidative metabolism). IP seems to involve mitochondrial K-ATP channels affecting mitochondrial membrane potential and thereby potentially MIBI uptake. The study evaluated the performance of MPI with MIBI as a tracer to characterise the extent that severely ischaemic compromised myocardium was salvaged by IP. In a closed chest model, an ischaemic preconditioned group (8 pigs) subjected to IP before introducing a 45 min period of catheter based coronary occlusion was compared with a control group (9 pigs). Area at risk'(AAR), infarct size (IS) and IS relative to AAR was determined by MIBI SPECT and by a standard histochemical method. The results demonstrated that infarct size was significantly smaller in the IP group both relative to left ventricle (IS/LV) and to area at risk (IS/AAR). Both AAR/LV and IS/LV, however, were greater when measured by MPI than with histochemistry. There was no difference in the ratio between infarct size and area at risk (IS/AAR). In conclusion, MPI with MIBI is a reliable measurement of infarct reduction by ischaemic preconditioning. Myocardium affected by recent ischaemia is correctly distinguished as viable by MPI in early reperfusion, when compared to a standard histochemical technique.

Animals↗
PubMed2002

[Resuscitation].

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Adult↗
PubMed2002

Effect of carvedilol on microcirculatory and glucose metabolic regulation in patients with congestive heart failure secondary to ischemic cardiomyopathy.

In a randomized (2:1), double-blinded design study, we studied 25 patients with congestive heart failure (66 +/- 9 years, ejection fraction 30 +/- 7%) before and after 23-week treatment with the beta blocker carvedilol 25 mg twice daily (n = 17) or placebo (n = 8) in addition to standard therapy. Using dynamic positron emission tomography, myocardial perfusion at rest and perfusion reserve after dipyridamole (0.56 mg/kg/min) were measured. Myocardial glucose uptake and plasma levels of catecholamines were also estimated. Carvedilol treatment reduced the rate-pressure product (8,781 +/- 2,672 vs 6,342 +/- 1,346, p <0.01) and improved ejection fraction (29 +/- 7% vs 37 +/- 11%, p <0.001), whereas no changes were observed in the control group. Perfusion at rest was unchanged in the placebo group (0.81 +/- 0.17 vs 0.86 +/- 0.23 ml/g/min, p = NS), whereas the carvedilol-treated group showed a significant reduction (0.88 +/- 0.26 vs 0.75 +/- 0.16 ml/g/min, p <0.05). Dipyridamole-induced hyperemia was significantly reduced after carvedilol treatment (1.51 +/- 0.45 vs 1.31 +/- 0.51 ml/g/min, p <0.001), whereas myocardial perfusion reserve was unaltered. Carvedilol did not alter myocardial glucose uptake (0.33 +/- 0.14 vs 0.32 +/- 0.12 micromol/g/min, p = NS) or the plasma catecholamines levels. We therefore conclude that in patients with congestive heart failure, carvedilol reduced resting and hyperemic perfusion. No effect on glucose uptake or catecholamine levels was observed. The reduced perfusion at rest must reflect reduced perfusion demand and thereby a higher threshold for myocardial ischemia and protection against myocardial damage or malignant arrhythmia. These effects may serve as a pathophysiologic explanation for the reduced mortality in patients with congestive heart failure who receive carvedilol.

Aged↗
PubMed2002

Effect of oral nitroglycerin and cold stress on myocardial perfusion in areas subtended by stenosed and nonstenosed coronary arteries.

Physical obstruction and coronary vasoconstriction mediated by adrenergic stress are believed to be responsible for episodes of myocardial hypoperfusion and angina. Nitroglycerin relieves symptoms by reducing preload and dilating epicardial vessels. The net perfusion change and relation to stenosis severity of nitroglycerin and adrenergic stress have been debated. This study aimed to evaluate whether oral nitroglycerin and adrenergic stress alters perfusion in myocardial segments subtended by stenosed and nonstenosed coronary arteries. Myocardial perfusion was quantified (using N-13-ammonia positron emission tomography [PET]) at rest, after oral nitroglycerin 400 microg, and after cold stress in 25 patients with coronary artery disease (62 +/- 9 years, 21 men) and in 30 controls (34 +/- 9 years, 22 men). Myocardial perfusion was quantified in areas supplied by stenosed (>70%) and nonstenosed (<30%) coronary arteries. The cold pressor test did not significantly alter myocardial perfusion in any of the groups. However, when normalized for rate-pressure product, the response in stenosed areas showed a significantly more pronounced reduction compared with nonstenosed areas (0.78 +/- 0.18 vs 0.64 +/- 0.19 ml/g/min, p <0.005 and 0.86 +/- 0.19 vs 0.73 +/- 0.24 ml/g/min, p <0.05, p <0.05) for intergroup comparison. In both stenosed areas and nonstenosed areas nitroglycerin increased perfusion (0.51 +/- 0.14 vs 0.60 +/- 0.17 ml/g/min, p <0.05 and 0.56 +/- 0.14 vs 0.61 +/- 0.17 ml/g/min, p <0.05). Nitroglycerin did not alter myocardial perfusion in the control group. There was a negative correlation between the cold pressor test response and stenosis severity (r(2) = 0.17, p <0.046), whereas this was not the case for nitroglycerin. In patients with coronary artery disease, myocardial segments supplied by stenosed coronary arteries showed an altered perfusion response to adrenergic stress. Oral nitroglycerin increased myocardial perfusion irrespective of the presence of a stenosis.

Administration, Oral↗
PubMed2002

Impact of daily life myocardial ischemia in patients with chronic reversible and irreversible myocardial dysfunction.

Repetitive myocardial ischemia during daily life has been suggested as the underlying mechanism of reversible myocardial dysfunction, which may progress into a hibernating state. Thirty-seven patients with ischemic cardiomyopathy (ejection fraction 35 +/- 7%) underwent positron emission tomography (N-13 ammonia and 18-F-fluoro-2-deoxy-glucose [FDG]) and exercise testing before coronary artery bypass grafting (CABG) and 48- hour ambulatory electrocardiographic monitoring to detect ischemia before CABG and 6 months postoperatively. Reversibility of regional myocardial dysfunction was detected by echocardiographic follow-up at 5 days, 2 months, and 6 months after the operation. Preoperatively, ischemic episodes during daily activities were more common (2 [25th to 75th percentiles 0 to 4] vs 0 episodes, p <0.01) and duration of ischemia longer (9 [25th to 75th percentiles 0 to 37] vs 0 [25th to 75th percentiles 0 to 1] minutes, p <0.02) in patients with reversible dysfunction (n = 15) than in patients with irreversible dysfunction (n = 22). The number of ischemic episodes per patient correlated with the numbers of reversibly dysfunctional segments (p = 0.003), viable segments as seen by positron emission tomography (p <0.05), and flow-metabolic mismatch segments (p <0.05). CABG eliminated ambulatory ischemic episodes in patients with reversible dysfunction (0 episodes, p <0.05 vs before CABG). Preoperatively, all patients with reversible dysfunction had a positive exercise test (14 of 15 patients), whereas daily life ischemia was present in 60% of patients. Reversibly dysfunctional segments in patients with ambulatory ischemia had faster recovery of function (15 of 28 patients vs 2 of 12 patients recovered at 5 days, p <0.05), higher FDG uptake (0.86 +/- 0.19% vs 0.71 +/- 0.24%, p <0.05) than in patients without ambulatory ischemia, whereas perfusion was similar (0.63 +/- 0.20 and 0.62 +/- 0.19 ml/g/min). Thus, exercise-induced myocardial ischemia is associated with reversibility of myocardial dysfunction, but not all patients with reversible ischemic cardiomyopathy have ischemic attacks during daily life.

Activities of Daily Living↗
PubMed2002

Coronary collaterals during single-vessel coronary angioplasty: effects of nitroglycerin.

BACKGROUND: Although the protective role of collaterals in coronary artery disease (CAD) is well known, the influence of drugs on collateral function remains controversial. HYPOTHESIS: We aimed to investigate prospectively the prevalence of spontaneously visible and recruitable coronary collaterals in consecutive patients with single-vessel CAD and the effect of systemic administration of nitroglycerin on these types of collaterals during percutaneous transluminal coronary angioplasty (PTCA). METHODS: Ipsi- and contralateral coronary artery contrast injections were performed before and during PTCA. Simultaneously with balloon occlusion, we measured coronary artery occlusion pressure via the balloon catheter. All measurements were repeated after administration of 0.5 mg of nitroglycerin intravenously. RESULTS: Of 101 consecutive patients, 24% had spontaneously visible and 30% had recruitable collaterals. Contralateral collaterals were five times more frequent than ipsilateral collaterals. Presence of collaterals was highly associated with the degree of coronary stenosis. Coronary occlusion pressure was higher in patients with than in those without collaterals. Collaterals prevented pain and ischemia during PTCA, and in this respect spontaneously visible collaterals were more effective than recruitable collaterals. There was no effect of systemic administration of nitroglycerin on appearance or occlusion pressure of coronary collaterals. CONCLUSION: Coronary collaterals were found in more than half of patients with single-vessel CAD, as the prevalence of recruitable collaterals was slightly higher than that of spontaneously visible collaterals. Nitroglycerin did neither recruit nor augment coronary collaterals.

Adult↗
PubMed2002

Prescription of anti-anginal drugs in relation to exercise tests and coronary angiography. A 1-year population-based study of two Danish counties.

BACKGROUND: The cardiac diagnostic examination activity in a population should ideally mirror age and gender characteristics of the prevalence of ischemic heart disease. In this study, the prescription of anti-anginal drugs in relation to morbidity and mortality brought on by ischemic heart disease, and in relation to exercise tests and coronary angiography, is analyzed. METHODS: The study population comprised two Danish counties with a total of 896,954 inhabitants. We obtained data on all prescriptions of nitrates, adrenergic beta-antagonists, and calcium channel blockers from regional pharmaceutical registers. Data on all patients who took an exercise test or underwent coronary angiography were derived from regional health authority registers. Data on ischemic heart mortality and on the incidence of myocardial infarction were gathered from the national register of causes of death and hospital registers. RESULTS: Only patients receiving nitrates had an age and gender profile matching that of those who died from ischemic heart disease or who suffered from myocardial infarction (correlation coefficients 0.95-0.99). Judging from the prescription of nitrates, relatively few elderly patients, especially women older than 60-69 years, were referred for a cardiac examination. CONCLUSIONS: The prescription of nitrates seems useful as a surrogate marker for ischemic heart disease. Elderly patients, especially women, seem to be treated with anti-anginal medication without any diagnostic evaluation.

Journal Article↗
PubMed2002

Establishing primary angioplasty as the preferred treatment for acute myocardial infarction.

OBJECTIVE: To report procedural results and mortality rates from the first 4 years after establishing primary angioplasty as the preferred treatment for acute myocardial infarction in a single Scandinavian centre. DESIGN AND RESULTS: From August 1995 to October 1999 all patients with the diagnosis of suspected acute myocardial infarction (n = 529, mean age 62 +/- 13 years, 72% men), either transferred (73%) or directly admitted to our institution for coronary angiography with the intention of performing primary percutaneous coronary intervention (primary PCI), were prospectively registered. Procedural success in terms of residual stenosis < or = 30% and a final Thrombolysis in Myocardial Infarction (TIMI) 3 flow was achieved in 94 and 85% of patients treated, respectively. In-hospital delay and procedure times decreased significantly during the 4-year study period. A low in-hospital mortality was observed in each of the 4 years studied (8.7, 8.7, 7.7 and 6.0%). CONCLUSION: In a centre with both directly admitted and transferred patients primary angioplasty can be established as the preferred treatment for acute myocardial infarction with an initially low complication and mortality rate. During the first years after implementing the primary angioplasty programme a learning effect can be anticipated with reductions in procedural times.

Acute Disease↗
PubMed2002

Coronary artery bypass surgery in heart failure patients with chronic reversible and irreversible myocardial dysfunction: effect on heart rate variability.

It is unknown whether surgical revascularization of viable and chronic reversibly dysfunctional myocardium in patients with heart failure is associated with a favorable effect on the autonomic control of heart rate. We studied 38 coronary artery bypass surgery (CABG) patients with an ejection fraction of 36 +/- 7%. Before CABG, the patients underwent 48-hour ambulatory electrocardiographic monitoring to measure heart rate variability (HRV), echocardiography to assess left ventricular function, and positron emission tomography and low-dose dobutamine echocardiography to assess viability. Six months after CABG, ambulatory electrocardiographic monitoring and echocardiography were repeated to assess HRV and recovery of left ventricular function. In spite of viable myocardium and recovery of left ventricular function following CABG, HRV indices were reduced 6 months postoperatively. A potential prognostic benefit gained by revascularizing patients with viability may occur in spite of deteriorated autonomic control of heart rate.

Aged↗
PubMed2000

Effect of antianginal medication on resting myocardial perfusion and pharmacologically induced hyperemia.

Background. Patients scheduled for myocardial perfusion imaging are often taking several antianginal drugs. There is presently no consensus concerning a regimen of discontinuation before either rest or pharmacologic stress myocardial perfusion imaging. Whether antianginal treatment affects diagnostic sensitivity and specificity is not well documented. Methods and Results. The effect of the three most commonly used antianginal drugs (nitroglycerin, 400 micro g [NTG]; metoprolol, 50 mg [MET]; and amlodipine, 5 mg [AML]) on myocardial perfusion was tested in 49 patients (age, 63 +/- 8 years; 43 men) allocated prospectively to one of the treatments (NTG, n = 25; MET, n = 14; and AML, n = 10). All patients had documented coronary artery disease and were scheduled for elective percutaneous coronary intervention. Patients were studied once on treatment and once off treatment with an interval of 1 to 3 weeks. For NTG, the measurements were performed on the same day with an interval of 1 hour. The MET and AML groups were also studied during dipyridamole-induced hyperemia (0.56 mg. kg(-1). min(-1) for 4 minutes). So that a quantitative value of myocardial perfusion in milliliters per gram per minute could be obtained, myocardial perfusion was quantified with nitrogen 13 ammonia positron emission tomography as an average of the midventricular perfusion in each of the 3 vascular territories. NTG treatment increased the overall resting perfusion (0.75 +/- 0.18 vs 0.86 +/- 0.22, P <.05), whereas resting perfusion was reduced after MET treatment (0.92 +/- 0.14 vs 0.82 +/- 0.17, P <.05). AML treatment did not alter resting perfusion (0.87 +/- 0.22 vs 0.87 +/- 0.23, P = NS). Dipyridamole-induced hyperemia was reduced after treatment with MET (2.02 +/- 0.66 vs l.57 +/- 0.52, P <.001), whereas the hyperemic response was unchanged after treatment with AML (1.54 +/- 0.49 vs 1.86 +/- 0.91, P = NS). Conclusions. Antianginal medication can alter both resting and hyperemic myocardial perfusion and might affect the ability to detect flow-limiting stenosis. NTG increases perfusion, MET reduces perfusion, and AML does not affect perfusion. Larger-scale trials are warranted to establish a consensus for optimal antianginal medication for patients undergoing perfusion imaging.

Journal Article↗
PubMedDate not supplied

Effect of antianginal medication on resting myocardial perfusion and pharmacologically induced hyperemia.

BACKGROUND: Patients scheduled for myocardial perfusion imaging are often taking several antianginal drugs. There is presently no consensus concerning a regimen of discontinuation before either rest or pharmacologic stress myocardial perfusion imaging. Whether antianginal treatment affects diagnostic sensitivity and specificity is not well documented. Methods and results The effect of the three most commonly used antianginal drugs (nitroglycerin, 400 microg [NTG]; metoprolol, 50 mg [MET]; and amlodipine, 5 mg [AML]) on myocardial perfusion was tested in 49 patients (age, 63 +/- 8 years; 43 men) allocated prospectively to one of the treatments (NTG, n = 25; MET, n = 14; and AML, n = 10). All patients had documented coronary artery disease and were scheduled for elective percutaneous coronary intervention. Patients were studied once on treatment and once off treatment with an interval of 1 to 3 weeks. For NTG, the measurements were performed on the same day with an interval of 1 hour. The MET and AML groups were also studied during dipyridamole-induced hyperemia (0.56 mg. kg(-1). min(-1) for 4 minutes). So that a quantitative value of myocardial perfusion in milliliters per gram per minute could be obtained, myocardial perfusion was quantified with nitrogen 13 ammonia positron emission tomography as an average of the midventricular perfusion in each of the 3 vascular territories. NTG treatment increased the overall resting perfusion (0.75 +/- 0.18 vs 0.86 +/- 0.22, P <.05), whereas resting perfusion was reduced after MET treatment (0.92 +/- 0.14 vs 0.82 +/- 0.17, P <.05). AML treatment did not alter resting perfusion (0.87 +/- 0.22 vs 0.87 +/- 0.23, P = NS). Dipyridamole-induced hyperemia was reduced after treatment with MET (2.02 +/- 0.66 vs l.57 +/- 0.52, P <.001), whereas the hyperemic response was unchanged after treatment with AML (1.54 +/- 0.49 vs 1.86 +/- 0.91, P = NS). CONCLUSIONS: Antianginal medication can alter both resting and hyperemic myocardial perfusion and might affect the ability to detect flow-limiting stenosis. NTG increases perfusion, MET reduces perfusion, and AML does not affect perfusion. Larger-scale trials are warranted to establish a consensus for optimal antianginal medication for patients undergoing perfusion imaging.

Amlodipine↗