Suppressed phospholamban levels differentiate irreversibly dysfunctional from hibernating myocardium in humans

OBJECTIVES

We studied whether dysfunction of human hibernating (HIB) and irreversibly dysfunctional myocardium (IRDM) are associated with altered levels of the sarcoplasmatic reticulum calcium handling proteins Ca2+-ATPase (SERCA2a) and its inhibitor phospholamban (PLB).

DESIGN

In 12 patients myocardial biopsies were taken during bypass surgery and analysed for contents of these proteins. We classified regions as control, HIB, or IRDM based on echocardiographic studies before and 6 months after surgery.

RESULTS

SERCA2a content (mean+/-SEM) was similar to control in HIB and IRDM (2.6 +/- 1.7, 3.8 +/- 2.0, and 3.4 +/- 1.9 units/g non-collagen protein (NCP), p = 0.40). PLB content was similar to control in HIB (2.6 +/- 0.4 and 3.5 +/- 0.5 units/microg NCP) but reduced in IRDM (0.9 +/- 0.2 units/microg NCP, p < 0.05). SERCA2a:PLB ratio, an indicator of SERCA2a activity, did not differ between control and HIB (1.2 +/- 0.3 and 1.4 +/- 0.4 units/microg NCP) but was increased in IRDM (5.1 +/- 1.7 units/microg NCP, p < 0.05).

CONCLUSIONS

Inappropriate SERCA2a activity due to suppressed PLB levels may represent a maladaptive mechanism in chronic ischemic myocardium being causally linked to irreversibility of left ventricular dysfunction.

Three-Year Outcome After Coronary Stenting Versus Bypass Surgery for the Treatment of Multivessel Disease

Background— The primary results of Arterial Revascularization Therapy Study reported a greater need for repeated revascularization after percutaneous coronary intervention with stenting (PCI). However, PCI was less expensive than coronary artery bypass grafting (CABG) and offered the same degree of protection against death, stroke, and myocardial infarction.

Methods and Results— Patients with multivessel disease (n=1205) were randomly assigned to either CABG or PCI and followed up for up to 3 years. Survival rates without stroke or myocardial infarction were similar in each group at 1 year and 3 years (90.5% versus 91.4% for PCI versus CABG at 1 year and 87.2% versus 88.4% for PCI versus CABG at 3 years). However, the respective repeat revascularization rates were 21.2% and 26.7% at 1 and 3 years in patients allocated to PCI, compared with 3.8% and 6.6% in patients allocated to CABG ( P <0.0001). Diabetes ( P <0.0009) and maximal pressure for stent deployment ( P <0.002) are the strongest independent predictors of events at 3 years after PCI, whereas left anterior descending coronary artery grafting ( P <0.006) is the best predictor of event-free survival at 3 years after CABG. The incremental cost of surgery compared with PCI for an event-free patient was 19 257 at 1 year but decreased to 10 492 at 3 years. It remained at 142 391 at 3 years when revascularization procedures were excluded in the efficacy end point, however.

Conclusions— Three-year survival rates without stroke and myocardial infarction are identical in both groups, and the cost/benefit ratio of stenting is determined primarily by the increasing need for revascularization in the PCI group.

Revascularization in multivessel disease: comparison between two-year outcomes of coronary bypass surgery and stenting

OBJECTIVE

The recent appreciation that stenting has improved the short- and long-term outcomes of patients treated with coronary angioplasty has made it imperative to reconsider the comparison between surgery and percutaneous interventions in patients with multivessel disease.

METHODS

One thousand two hundred five patients were randomly assigned to undergo bypass surgery or angioplasty with stent implantation when there was consensus between the cardiac surgeon and interventional cardiologist as to equivalent treatability. The primary clinical end point was freedom from major adverse cardiac and cerebrovascular events at 1 year. Major adverse cardiac and cerebrovascular events at 2 years constituted a secondary end point.

RESULTS

At 2 years, 89.6% of the surgical group and 89.2% of the stent group were free from death, stroke, and myocardial infarction (log-rank test P =.65). Among patients who survived without stroke or myocardial infarction, 19.7% in the stent group underwent a second revascularization, as compared with 4.8% in the surgical group (P <.001). At 2 years, 84.8% of the surgical group and 69.5% of the stent group were event-free survivors (log-rank test P <.001), and 87.2% in the surgical cohort and 79.6 % in the stent group were angina-free survivors (P =.001). In the diabetes subgroup, 82.3% of the surgical group and 56.3% of the stent group were free from any events after 2 years (log-rank test P <.001).

CONCLUSION

The difference in outcome between surgery and stenting observed at 1 year in patients with multivessel disease remained essentially unchanged at 2 years. Stenting was associated with a greater need for repeat revascularization. In view of the relatively greater difference in outcome in patients with diabetes, surgery clearly seems to be the preferable form of treatment for these patients.

Heart motion-adapted MR velocity mapping of blood velocity distribution downstream of aortic valve prostheses: initial experience

PURPOSE

To investigate blood flow velocities and shear rates at two distances downstream of an artificial aortic valve in patients.

MATERIALS AND METHODS

Blood velocity was quantified downstream of the valve prosthesis (for replacement after aortic valve stenosis or combined stenosis and regurgitation) in 10 patients by using a magnetic resonance (MR) cine velocity mapping method in which the imaging section position is adapted according to the excursion of the valvular plane of the heart. Two acquisitions were performed to display the blood velocity distributions one-fourth valve diameter and one valve diameter downstream of the valve and to quantify blood volumes and shear rates.

RESULTS

The velocity profiles measured during flow acceleration one-fourth valve diameter downstream were characterized by a distinct pattern of two lateral jets and one central jet of antegrade flow. High shear rates were found along the leaflet tips. The profiles obtained one valve diameter downstream were skewed, with varying velocity patterns among patients. Peak shear rates were found close to the vessel wall. With correction for through-plane motion of the valve, the mean apparent regurgitant fraction (+/- SD) was 14% +/- 6; the mean regurgitant fraction without correction was 9% +/- 5.

CONCLUSION

The described noninvasive procedure for velocity mapping enables measurements close to the valve and thus evaluation of blood flow patterns with respect to valve design in humans.

Energy stores and metabolites in chronic reversibly and irreversibly dysfunctional myocardium in humans

OBJECTIVES

Our goal was to study metabolic energy stores and lactate content in chronic reversibly and irreversibly dysfunctional myocardium.

BACKGROUND

It is unknown whether metabolism is deranged in chronic reversibly and irreversibly dysfunctional myocardium in humans. Semiquantitative histological examinations have shown altered mitochondrial morphology and glycogen accumulation in dysfunctional regions.

METHODS

We studied 25 patients with a mean ejection fraction of 38 +/- 9% scheduled for coronary artery bypass surgery. Regional perfusion and metabolism were assessed by positron emission tomography, and regional function was assessed by echocardiography. Perioperative myocardial biopsies were obtained from a control region and from a dysfunctional region. We analyzed biopsies for contents of noncollagen protein (NCP), ATP, ADP, AMP, glycogen and lactate. Six months after surgery we assessed wall motion by echocardiography to group patients in those with (n = 11) and without (n = 14) functional improvement.

RESULTS

Reversibly dysfunctional myocardium had reduced perfusion (0.59 +/- 0.16 vs. 0.69 +/- 0.20 ml/g/min, p < 0.05), similar glucose-tracer uptake (92 +/- 12 and 95 +/- 14%), ATP/ADP ratio (2.4 +/- 1.1 and 2.4 +/- 0.7), glycogen content (631 +/- 174 and 632 +/- 148 nmol/microg NCP) and lactate levels (59 +/- 27 and 52 +/- 29 nmol/microg NCP) compared with control regions. Irreversibly dysfunctional regions (n = 14) had severely reduced perfusion (0.48 +/- 0.15 vs. 0.72 +/- 0.12 ml/g/min, p < 0.001) and glucose-tracer uptake (52 +/- 16 vs. 94 +/- 15%, p < 0.001), reduced ATP/ADP ratio (1.5 +/- 0.9 vs. 2.3 +/- 0.9, p < 0.05), similar glycogen content (579 +/- 265 vs. 593 +/- 127 nmol/microg NCP) and increased lactate levels (114 +/- 52 vs. 89 +/- 24 nmol/microg NCP, p < 0.01) compared with control regions.

CONCLUSIONS

Contents of metabolic energy stores and lactate in chronic reversibly dysfunctional myocardium were preserved. In contrast, energy stores were depleted in myocardium without functional recovery after revascularization.

[DANAMI. A Danish study of invasive versus conservative treatment of patients with post-infarction ischemia who had received thrombolytic therapy]

INTRODUCTION

To compare an invasive strategy employing percutaneous transluminal coronary angioplasty (PTCA) or coronary artery by-pass grafting (CABG) with a medical strategy in patients who had received thrombolytic treatment for first acute myocardial infarction (AMI), and with signs of inducible ischaemia.

METHODS

In a prospective study 1008 patients were randomized, 503 to invasive treatment, of whom 266 (52.9%) had PTCA, and 147 (29.2%) CABG, 505 to conservative treatment, of whom eight (1.6%) were revascularized within two months.

RESULTS

After a median follow-up of 2.4 years the mortality in the invasive group was 3.6% vs. 4.4% (p = 0.45) in the conservative group, re-infarction incidence was 5.6% vs. 10.5% (p = 0.0038) and percentage of admissions with unstable angina was 17.9% vs. 29.5% (p < 0.00001).

DISCUSSION

We conclude that post-infarct patients with inducible ischaemia should be referred to coronary angiography and revascularised accordingly.

A new method for quantitative evaluation of perceived sounds from mechanical heart valve prostheses

Closing clicks from mechanical heart valve prostheses are transmitted to the patient's inner ear mainly in two different ways: as acoustically transmitted sound waves, and as vibrations transmitted through bones and vessels. The purpose of this study was to develop a method for quantifying what patients perceive as sound from their mechanical heart valve prostheses via these two routes. In this study, 34 patients with implanted mechanical bileaflet aortic and mitral valves (St Jude Medical and On-X) were included. Measurements were performed in a specially designed sound insulated chamber equipped with microphones, accelerometers, preamplifiers and a loudspeaker. The closing sounds measured with an accelerometer on the patient's chest were delayed 400 ms, amplified and played back to the patient through the loudspeaker. The patient adjusted the feedback sound to the same level as the 'real-time' clicks he or she perceived directly from his or her valve. In this way the feedback sound energy includes both the air- and the bone-transmitted energies. Sound pressure levels (SPLs) were quantified both in dB(A) and in the loudness unit sone according to ISO 532B (the Zwicker method). The mean air-transmitted SPL measured close to the patient's ear was 23 +/- 4 dB(A). The mean air- and bone-transmitted sounds and vibrations were perceived by the patients as an SPL of 34 +/- 5 dB(A). There was no statistically significant difference in the perceived sound from the two investigated bileaflet valves, and no difference between aortic and mitral valves. The study showed that the presented feedback method is capable of quantifying the perceived sounds and vibrations from mechanical heart valves, if the patient's hearing is not too impaired. Patients with implanted mechanical heart valve prostheses seem to perceive the sound from their valve two to three times higher than nearby persons, because of the additional bone-transmitted vibrations.

Assessment of perceived mechanical heart valve sound level in patients

BACKGROUND AND AIM OF THE STUDY

When mechanical heart valves close, they generate an impulse that is transmitted to the patient's inner ear by two routes: (i) As acoustically transmitted sound waves; and (ii) as vibrations transmitted through bones and vessels. The aim of this study was to quantitate what patients perceive as sound from their mechanical heart valve prostheses - including both air-transmitted sound waves and bone-transmitted vibrations.

METHODS

Thirty-four patients with implanted mechanical bileaflet aortic and mitral valves (St. Jude Medical and On-X) were included in the study. Measurements were performed in a specially designed sound-insulated chamber equipped with microphones, accelerometers, preamplifiers and a loud-speaker. The closing sounds measured by an accelerometer on the patient's chest were delayed 400 ms, amplified and played back to the patient through the loudspeaker. The patient adjusted the feedback sound to the same level as the 'real-time' clicks they perceived directly from their valve. In this way the feedback sound energy includes both the air- and bone-transmitted energies. Sound pressure levels (SPL) were quantitated in both dB(A) and in loudness units (sones) according to ISO 532B (Zwicker method).

RESULTS

The mean air-transmitted SPL measured close to the patient's ear was 23 +/- 4 dB(A). The total air-and bone-transmitted sounds and vibrations were perceived by the patients as a SPL of 34 +/- 5 dB(A). There was no statistically significant difference in perceived sound from the two bileaflet valves investigated, and no difference between aortic and mitral valves.

CONCLUSIONS

The study showed that the presented feedback method is capable of quantitating the perceived sounds and vibrations from mechanical heart valves, if the patient's hearing is not too impaired. Patients with implanted mechanical heart valve prostheses seem to perceive the sound from their valve two to four times higher than nearby persons, because of the additional bone-transmitted vibrations.

Development of velocity profiles and retrograde flow in the porcine abdominal aorta under different haemodynamic conditions

Low and/or oscillating wall shear stresses are related to the development of atherosclerosis and this oscillation is influenced by changes in basic haemodynamics (exercise). The objective of this study was to provide in vivo data on the development of velocity profiles and oscillating blood velocities in the abdominal aorta under varying haemodynamic conditions. Six anaesthetized, 90-kg pigs were used in the study. Abdominal aortic velocity profiles across the anterior-posterior diameter were acquired at different axial positions using 10 MHz pulsed Doppler ultrasound. Measurements were obtained under normal conditions and during cardiac pacing up to 170 beats/min. Velocity profiles were obtained during heart rates ranging between 58 and 169 beats/min, and during flow rates ranging between 0.57 and 2.89 l/min. Main outcome measures included minimum velocities, frequency index, shape of velocity profiles (velocity distribution index), Reynolds' numbers, and Womersley's frequency parameter. Velocity profiles were blunted, with lowest velocities at the distal posterior vessel wall. Multiple regression analysis showed the development of velocity profiles to be inversely correlated with the pulsatility index, Womersley's frequency parameter and the mean Reynolds' number (r = 0.89, p < 0.0005). Minimum velocities were negatively correlated with the PI, Womersley's frequency parameter and positively with the mean Reynolds' number (r = 0.94, p < 10(-8)). Retrograde velocities (and hence oscillating wall shear stresses) were present at mean Reynolds' number < 1000. The oscillation of blood velocities at the wall in the porcine abdominal aorta was highly dependent on general haemodynamics (i.e. flow, heart rate and vessel diameter as expressed in the Reynolds' numbers and Womersley's frequency parameters). The velocity profiles in the abdominal aorta were found to be far from parabolic. These findings have important implications for the understanding and future modelling of the complex haemodynamics in the abdominal aorta and their relation to the development of atherosclerotic disease.

High-frequency pressure fluctuations measured in heart valve patients

BACKGROUND AND AIM OF THE STUDY

Due to the risk of thromboembolic complications, mechanical heart valve patients require life-long anticoagulant therapy, in contrast to bioprosthetic valves. The reason for this is still not fully understood. In vitro studies have demonstrated the presence of cavitation bubbles in the vicinity of mechanical heart valves, but not of bioprosthetic valves. When cavitation bubbles collapse, they release a significant amount of energy, which may damage the formed elements of the blood. A correlation between the presence of cavitation bubbles and high-frequency pressure oscillations has been established in vitro. Thus, the aim of this study was to measure and quantify high-frequency pressure oscillations in patients with normal, bioprosthetic or mechanical aortic valves.

METHODS

Measurements were performed in six patients with normal aortic valves after coronary bypass surgery, in five patients fitted with a Carpentier-Edwards pericardial bioprosthesis, and in nine patients fitted with a St. Jude Medical or CarboMedics aortic valve. High-frequency pressure fluctuations were measured intraoperatively using a hydrophone placed near the aortic annulus. The root mean square (RMS) value of the high-frequency pressure signals were calculated in the frequency range 35-150 kHz.

RESULTS

High-frequency pressure fluctuations, with intensities above the noise floor, were registered only in the vicinity of mechanical heart valve prostheses, and not in the vicinity of normal or bioprosthetic valves. The mean value of RMS pressure fluctuations was 0.5 Pa for normal aortic valves, 0.8 Pa for bioprosthetic valves, and 67 Pa for mechanical valves.

CONCLUSIONS

This study is the first to show the presence of high-frequency pressure fluctuations in patients with mechanical valves.

Medtronic Hall versus St. Jude Medical mechanical aortic valve: downstream turbulences with respect to rotation in pigs

BACKGROUND AND AIMS OF THE STUDY

Turbulences downstream of mechanical aortic valves are known to contribute to most valve-related complications such as thrombosis, embolization or damage to blood components. In vitro studies have demonstrated the impact of the orientation of prostheses on transvalvular energy loss. This study evaluates the influence of valve orientation on turbulences in the supravalvular aorta in pigs.

METHODS

A rotation device which could carry a Medtronic Hall (MH) or St. Jude Medical (SJM) aortic valve prosthesis (23 mm) was constructed and implanted into four healthy pigs. Turbulence measurements using pulsed Doppler ultrasonography were carried out 3 cm downstream of the valve, while the prostheses were rotated in 45 degrees steps. Reynold's normal stress values (RNS) were calculated as key markers for turbulent stresses.

RESULTS

Turbulences downstream of MH and SJM valves demonstrated a significant change with rotation. The MH valve showed minimum RNSmean values with orientation of the large orifice to the right posterior aortic wall, which is the area of highest velocities during ejection. With this orientation, aortic flow almost complied with physiologic conditions. Increase of turbulence was observed with any other position. The SJM valve revealed significant turbulent flow at any orientation. Minimum RNSmean values were also measured with one orifice facing the right posterior wall of the aorta.

CONCLUSION

With optimum orientation (major orifice facing the right posterior aortic wall) the MH valve matches the aortic flow pattern to near-normal physiology. The flow patterns of the SJM valve are less susceptible to rotation, but cannot attain the optimum RNS values of the MH prosthesis.

The influence of propofol and midazolam/halothane anesthesia on hepatic SvO2 and gastric mucosal pH during cardiopulmonary bypass

OBJECTIVE

Because propofol is known to reduce vascular resistance, the objective of this study was to compare the indices of hepatosplanchnic circulation and oxygenation during cardiopulmonary bypass (CPB) in patients anesthetized with either propofol or midazolam/halothane.

DESIGN

A prospective, randomized, nonblinded study.

SETTING

A university hospital.

PARTICIPANTS

Twenty patients undergoing cardiac surgery with CPB.

INTERVENTIONS

Nine patients were anesthetized with propofol/fentanyl/pancuronium and 11 patients were anesthetized with midazolam/halothane/fentanyl/pancuronium. All patients had a nasogastric tonometer tube and two fiberoptic thermodilution catheters inserted; one in the pulmonary artery and one in the upper right hepatic vein. During bypass, SvO2s were measured from the venous line of the heart-lung machine.

MEASUREMENTS AND MAIN RESULTS

Gastric mucosal pH (pHi) was measured prebypass, 30 minutes after the start of CPB, and just before weaning off CPB. Hepatic SvO2 (HSvO2) values were recorded every 5 minutes. The pH gap was less at 30 minutes of hypothermic CPB in the propofol group. In the midazolam/halothane group, the HSvO2 decreased after the start of rewarming, whereas in the propofol group the values remained almost at the prebypass levels. At the end of rewarming, the HSvO2 was almost identical in the two groups.

CONCLUSION

Propofol preserved the HSvO2 during CPB and produced a more optimal relationship between the hepatosplanchnic blood flow and oxygen consumption.

CABG shortly after AMI treated with thrombolysis: an analysis of the surgical group and a comparison with PTCA in the DANAMI study. Danish multicenter randomized study of invasive versus conservative treatment in patients with inducible ischemia after thrombolysis in acute myocardial infarction

OBJECTIVE

To present surgical results of the DANAMI study comparing conservative and invasive treatment of postinfarction myocardial ischaemia and to compare these with percutaneous transluminal angioplasty (PTCA) which was the alternative invasive treatment in that study.

METHODS

A group of 413 patients with verified acute myocardial infarction treated with thrombolysis within 12 h of the onset of symptoms, who demonstrated postinfarction myocardial ischaemia were treated with coronary artery bypass grafting (CABG) or PTCA. Patients with left main lesions, three-vessel disease, two-vessel disease with more than three stenoses and patients with occlusions of a non-infarct related vessel had primary CABG. Patients with 1- and 2-vessel disease with not more than a total of three stenoses had PTCA. In case of failed PTCA patients had secondary CABG. The median distance from AMI to CABG was 45 days. PTCA was performed at a mean of 39 days after the infarction.

RESULTS

A total of 147 patients had CABG and 266 had PTCA. The operative mortality for CABG was 1.4%. No PTCA patients died in relation to the procedure, 0.8% developed acute myocardial infarction as a consequence of the procedure, 1.5% had acute CABG and 3.5% elective CABG due to failed PTCA. In spite of more severe coronary artery disease among the CABG patients there was no difference in survival at 2.4 years. The CABG group had significantly fewer episodes of unstable angina, 10.2% versus 25.6% (P = 0.0002). No CABG patients had re-do revascularisation at 2.4 years follow-up versus 15.4% of the PTCA patients. At 3 years 80% of the CABG patients were free of angina compared to the 61% of the PTCA group (P < 0.0001).

CONCLUSION

Low morbidity and mortality justifies the deferred elective revascularisation in patients with postinfarction myocardial ischaemia even in patients with silent ischaemia. There is no difference in survival at 2.4 years between CABG and PTCA but CABG offers more lasting results concerning incidence of stable and unstable angina than PTCA, which, however, is a valuable alternative in patients with less severe coronary artery disease.

Danish multicenter randomized study of invasive versus conservative treatment in patients with inducible ischemia after thrombolysis in acute myocardial infarction (DANAMI). DANish trial in Acute Myocardial Infarction

BACKGROUND

The aim of the DANish trial in Acute Myocardial Infarction (DANAMI) study was to compare an invasive strategy of percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG) with a conservative strategy in patients with inducible myocardial ischemia who received thrombolytic treatment for a first acute myocardial infarction (AMI).

METHODS AND RESULTS

Of the 503 patients randomized to an invasive strategy, PTCA was performed in 266 (52.9%) and CABG in 147 (29.2%) from 2 to 10 weeks after the AMI. Of the 505 patients in the conservative treatment group, only 8 (1.6%) had been revascularized 2 months after the AMI. The patients were followed up from 1 to 4.5 years. The primary end points were mortality, reinfarction, and admission with unstable angina. At 2.4 years' follow-up (median), mortality was 3.6% in the invasive treatment group and 4.4% in the conservative treatment group (not significant). Invasive treatment was associated with a lower incidence of AMI (5.6% versus 10.5%; P=.0038) and a lower incidence of admission for unstable angina (17.9% versus 29.5%; P<.00001). The percentages of patients with a primary end point were 15.4% and 29.5% at 1 year, 23.5% and 36.6% at 2 years, and 31.7% versus 44.0% at 4 years (P=<.00001) in the invasive and conservative treatment groups, respectively. At 12 months, stable angina pectoris was present in 21% of patients in the invasive treatment group and 43% in the conservative treatment group.

CONCLUSIONS

Invasive treatment in post-AMI patients with inducible ischemia results in a reduction in the incidence of reinfarction, fewer admissions due to unstable angina, and lower prevalence of stable angina. We conclude that patients with inducible ischemia before discharge who have received treatment with thrombolytic drugs for their first AMI should be referred to coronary arteriography and revascularized accordingly.

New semiautomated Doppler method for quantification of volumetric flow: intraoperative validation with multiplane transesophageal color Doppler imaging

We have validated a new semiautomated method for quantification of volumetric flow applied to multiplane transesophageal color Doppler mapping. This Doppler technique assumes only the incompressibility of the fluid and includes variations of flow area. By computing velocity vectors across a surface normal to the point of scanning, volumetric flow can be measured independently of the angle of incidence between the ultrasonic beam and the direction of blood flow. Mitral valvular flow rate was measured during surgery by transesophageal color Doppler echocardiography in 27 patients undergoing coronary artery bypass grafting at 45 sets of observations. The results were compared with those obtained by the thermodilution technique. The mean of the differences between the thermodilution technique and color Doppler echocardiography was 0.06 +/- 0.866 L/min for the mitral valvular flows (mean of differences [thermodilution-color Doppler] &/- 2 SDs of differences). Thus mitral valvular volumetric flow measured by this color Doppler method showed a close agreement to the thermodilution technique during surgery.

Wear patterns in the Sorin Bicarbon mechanical heart valve: a clinical explant study

BACKGROUND AND AIMS OF THE STUDY

Mechanical heart valve prostheses are subject to wear due to impact and friction between the occluder(s) and valve housing. Reference data on the extent of wear in vivo is lacking. Therefore, the aim of this study was to describe the wear pattern in Sorin Bicarbon valves explanted from humans for comparison with the findings established in an earlier in vitro study.

METHODS

We investigated eight valves explanted from seven patients, which had been functioning for more than six months and were returned to the Sorin Company for investigation. The protocol comprised: (i) initial visual inspection on receipt; (ii) stereomicroscopy after cleaning and disassembly; (iii) computed planimetry of the worn areas in the housing; (iv) pivot surface profilometry; and (v) scanning electron microscopy.

RESULTS

All wear depths and exposed areas of titanium were less than that predicted from in vitro figures. No valves were explanted due to mechanical failure and none of the patients had reported peripheral embolic events which could be attributed to valve wear. The extent of wear was comparable with that of other valves.

CONCLUSIONS

This descriptive study did not indicate any association between the Bicarbon valve wear characteristics and clinical complications. Clinical studies on valve performance are of paramount importance for elucidating this issue. The establishment of an independent body for studying explanted valves in collaboration with the manufacturers may promote the publication of findings which are of interest for the entire medical community.

Hemodynamic evaluation of a new bileaflet valve prosthesis: an acute animal experimental study

BACKGROUND AND AIMS OF THE STUDY

A newly developed heart valve (Medtronic Parallel) was tested in an acute animal experimental model.

METHODS

Five prototype valves were implanted in the aortic position in seven 90 kg pigs to enable acute evaluation of the hemodynamic performance in terms of turbulent stresses and transvalvular pressure drop. Turbulent stresses in the ascending aorta were measured using a 10 MHz perivascular Doppler echocardiographic transducer designed to measure the radical velocity component at 17 different points covering the aortic cross-sectional area.

RESULTS

The drop in transvalvular peak pressure measured with fluid-filled catheters showed a non-linear relationship with cardiac output and was always < 12 mmHg. The Reynolds normal stresses were < 60 N/m2 in systole within 50 ms time windows, which is insufficient to cause mechanical damage of the formed elements of the blood.

CONCLUSIONS

From a hemodynamic point of view the performance of the Medtronic Parallel aortic valve is fully acceptable and within the range of other similar, currently available mechanical valves.

Magnetic resonance imaging of blood velocity distribution around St. Jude medical aortic valves in patients

BACKGROUND AND AIMS OF THE STUDY

Complications after replacement of diseased heart valves with mechanical prostheses may be related to fluid dynamic disturbances. Magnetic resonance velocity mapping may allow quantitative, non-invasive, serial assessment of the blood velocity distribution around prosthetic heart valves in patients.

MATERIAL AND METHODS

Velocity mapping was performed in six patients with aortic St. Jude Medical valves. Axial velocity components were measured at three positions near the valve and correlated with earlier in vitro results and with earlier invasive measurements.

RESULTS

The velocity profiles downstream of the valve prostheses reflected the valve design and thus confirmed previous findings. In the one diameter downstream position blood flow velocities accelerated initially through the lateral orifices of the valve. Later in the acceleration phase the velocity profile became skewed and the antegrade velocity components increased in the part of the vessel corresponding to the central slit of the valve. Retrograde velocities occurred in part of the lateral orifice regions.

CONCLUSIONS

MR velocity mapping provides valuable information on velocity fields around prosthetic bileaflet aortic valves. The velocity fields from the present study disclose qualitative similarity to those previously obtained. The present study, however, suggests a more skewed velocity profile than predicted from former studies. More extensive studies on larger patient groups should be performed, also with other valve types in order to establish a bank of reference data.

Validation of a new transit time ultrasound flowmeter in man

OBJECTIVES

To validate the new CardioMed CM 4000 transit time ultrasound apparatus for intraoperative measurement of volume blood flow in vivo in man.

DESIGN

Open, prospective series.

MATERIALS

Thirteen patients undergoing in situ saphenous vein grafting for chronic critical leg ischaemia and 12 patients subjected to myocardial revascularisation with the internal thoracic artery as coronary bypass.

METHODS

During operations, volume blood flows were measured simultaneously by exsanguination from the cut distal end of the in situ saphenous vein graft or the internal thoracic artery and by the transit time flowmeter equipment. In addition, the feasibility to detect arteriovenous fistula during in situ saphenous vein grafting was examined.

RESULTS

Within the examined blood flow range, the volume blood flow determined by the transit time method corresponded to the directly measured blood flow. For in situ saphenous vein grafts: y = -2.4 + 0.95.x (r = 0.99; 35 measurements in 13 patients), and for internal thoracic artery grafts: y = -9.6 + 1.1.x (r = 0.99; 21 measurements in 12 patients), where y is blood flow determined by transit time, and x is directly measured blood flow by exsanguination (r = correlation coefficient) as calculated by the least squares regression method. Fistula detection was easy and swift.

CONCLUSIONS

The transit time apparatus was simple to use during intraoperative settings and gave fast, precise measurements of volume blood flow.

What force can the myocardium generate on a prosthetic mitral valve ring? An animal experimental study

Data on the magnitude of forces which can be generated by the myocardium on a prosthetic heart valve ring are not available from the literature. Therefore, we implanted strain gauge mounted 29 mm original specification Edwards-Duromedics mitral valve prostheses in 13 pigs. The valves were implanted in both anatomic and anti-anatomic orientation. In order to estimate the forces on the valve ring, acute in vivo measurements of the dynamic deformation of the valve ring were performed and correlated with the stiffness of the same valves measured in vitro. In the post cardioplegic heart of the anesthetized pigs there was a maximum force developed by the myocardium of 6-8 N on the valve ring with a resulting maximum deformation of 40 microns with valves mounted in the anatomic position. These findings have implications for design of future mechanical mitral valves and for mitral rings used for mitral valvuloplasty. These data can also be used as reference for evaluation of safety limits in existing valves in terms of their physical properties. Based on the direction of the maximum myocardial force acting on the mitral valve ring and the difference in compliance of the valve ring along the pivotal or orthogonal axis, it is indicated from that these acute porcine studies that bileaflet valves in the mitral position are subjected to less deformation when implanted 60 degrees counter-clockwise to the native mitral intercommisural line.

Turbulent stresses downstream of three mechanical aortic valve prostheses in human beings

High levels of turbulent stresses resulting from disturbed blood flow may cause damage to red blood cells and platelets. The purpose of this study was to evaluate the spatial distribution and temporal development of turbulent stresses downstream of three mechanical aortic valve prostheses in human subjects: the St. Jude Medical, the CarboMedics, and the Starr-Edwards silicone rubber ball. Blood velocity measurements were taken at 17 measuring points in the cross-sectional area of the ascending aorta 5 to 6 cm downstream of the aortic anulus with the use of a perivascular pulsed Doppler ultrasound system. Turbulence analysis was done for each of the 17 measuring points by calculating the radial Reynolds normal stresses within 50 msec overlapping time windows during systole. By coordinating the calculated Reynolds normal stress values for each time window and for all measuring points, computerized two-dimensional color-coded mapping of the turbulent stress distribution during systole was done. For the St. Jude Medical valves the highest Reynolds normal stress (27 to 63 N/m2) were found along the central slit near the vessel walls. The temporal development and spatial distribution of Reynolds normal stresses for the CarboMedics valves were quite similar to those of the St. Jude Medical valves with maximum Reynolds normal stress values ranging from 19 to 72 N/m2. The typical Reynolds normal stress distribution for the Starr-Edwards silicone rubber ball valves was asymmetric, revealing the highest Reynolds normal stresses (11 to 56 N/m2) at various locations in the annular region between the ball and the vessel wall. The spatial distribution and temporal development of turbulent stresses downstream of the three investigated mechanical aortic valve prostheses correlated well with the superstructure of the valves. The maximum Reynolds normal stresses for the three valve types were in the same order of magnitude with exposure times sufficient to cause sublethal damage to red blood cells and platelets.

A new perivascular multi-element pulsed Doppler ultrasound system for in vivo studies of velocity fields and turbulent stresses in large vessels

A pulsed Doppler ultrasound (PDU) multi-element system was developed for perivascular registration of velocity fields and turbulence in large vessels. In vivo evaluation and comparison with hot-film anemometry (HFA) was performed. C-shaped shells were designed with holes to fit five small 10 MHz ultrasonic probes directed at five measuring points along a diameter perpendicular to the vessel axis. By rotating the shell in 45 degrees steps, blood velocities were measured in 17 points covering the entire cross-sectional vessel area. Measurements were performed in the ascending aorta and at three axial locations in the descending thoracic aorta in pigs. Simultaneous PDU and HFA measurements were performed distal to induced vascular stenoses of different degrees. Three-dimensional visualisation of velocity profiles was made, and Reynolds normal stresses (RNS) were calculated for different levels of turbulence intensities based on the simultaneous PDU and HFA measurements. The velocity profiles in the ascending aorta were skewed at top systole with the highest velocities towards the posterior wall. In the descending thoracic aorta at the ligmentum of Botalli, the velocity profiles were skewed throughout the entire systole with the highest velocities at the right anterior vessel wall. Further downstream in the descending aorta the velocity profiles appeared blunter. The frequency response of the modified PDU system was determined by a 'random noise test' revealing an upper -3dB cut-off frequency of approximately 200 Hz. Regression analysis showed a linear relationship between RNS measured with PDU and RNS measured with HFA (r = 0.93). Two vessel diameters distal to a 75% stenosis RNS up to 28 N m-2 were measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessing the severity of aortic valve stenosis by spectral analysis of cardiac murmurs (spectral vibrocardiography). Part I: Technical aspects

Assessing the severity of aortic stenosis remains an important clinical problem. The turbulent pressure fluctuations generated by the confined jet down-stream of the stenotic valve produce vibrations in the aortic wall. These vibrations are transmitted through the chest to the skin surface, where they can be measured as systolic ejection murmurs. The purpose of the present study was to find the relationship between the severity of aortic valve stenosis and the frequency content of the precordial systolic murmurs, and to evaluate the transthoracic attenuation of murmurs and its variation from patient to patient. Twenty-four patients with clinical signs of aortic stenosis underwent cardiac catheterization to measure the peak transvalvular pressure difference. The mean energy density spectrum of the measured systolic precordial murmurs was calculated and the murmur energy ratio between 100-500 Hz and 20-500 Hz was correlated to the transvalvular pressure difference. The inter-individual variability of the transthoracic attenuation was evaluated by calculating the transthoracic transfer function from simultaneous measurements of precordial vibrations at the second right intercostal space and intravascular recordings of high frequency pressure fluctuations in the ascending aorta. The transvalvular pressure difference and the square root of the murmur energy ratio correlated well (r = 0.81, SEE = 27 mmHg). In the frequency range from 10-500 Hz the transthoracic transfer function could be modelled by a low-pass filter function with a low frequency attenuation of 36 +/- 7.7 dB (mean +/- SD), a corner frequency of 26 +/- 12 Hz and an attenuation slope of -29 +/- 7.9 dB/decade. Spectral analysis of systolic murmurs might be an attractive non-invasive addition to the array of techniques already in use for assessing the severity of aortic stenosis. It is a simple and cost effective technique, and requires less skill and time for data analysis than conventional methods.

Three dimensional visualisation of velocity profiles in the normal porcine pulmonary trunk

OBJECTIVE

The aim was to obtain detailed data of velocity profile development in the porcine pulmonary trunk.

METHODS

Hot film anemometry was used for point blood velocity measurements in the entire cross sectional area one diameter downstream of the normal porcine pulmonary valve. Computerised three dimensional visualisations of the spatial and temporal development of blood velocity profiles were made. Measurement series were conducted under spontaneous and stressed haemodynamic conditions in 16 pigs with a body weight of approximately 90 kg.

RESULTS

The velocity profiles revealed consistent temporal and spatial development characteristics. In the systolic acceleration phase the profile was flat, but during peak systole an initially counterclockwise rotation was seen; subsequently the profile turned clockwise and ultimately counterclockwise to become flat during early and late systolic deceleration phases.

CONCLUSIONS

These skewed, rotating velocity profiles are in conflict with the generally accepted assumption that the velocity profile in the pulmonary trunk is flat. The rotating skewness of the velocity profile in the porcine pulmonary trunk has not been described before. The reason for the rotating velocity profile is obscure.

Lowered threshold for ventricular fibrillation in amiodarone-treated pigs undergoing cardiopulmonary bypass and cardioplegic arrest with St. Thomas' cardioplegic solution

The antiarrhythmic agent amiodarone has been suspected of causing reduced cardiac performance after extracorporeal circulation and cardioplegic arrest in patients. This has recently been confirmed in an experimental model where pigs were exposed to cardiopulmonary bypass and cold cardioplegic arrest with Bretschneider's solution. Due to the high concentration of the cardio-depressant agent procain in Bretschneider's solution, it could be speculated whether it is the combination of amiodarone and this solution that may be potentially deleterious, rather than amiodarone alone. To investigate this, adult pigs (75 +/- 2 kg at surgery) were treated with amiodarone for 30 +/- 2 days (1400 mg/day: n = 8, untreated controls: n = 4, blind experiment), followed by exposure to cardiopulmonary bypass with universal cooling to 28 degrees C and topical cold cardioplegic arrest with St. Thomas' solution for 60 min. Apart from 1 g of calcium (Ca2+) at the end of bypass, no inotropic drugs were administered. Cardiac reserve was tested by right ventricular pacing (200 beats/min until death or up to 30 min). The two groups did not differ concerning preload or afterload, heart rate, cardiac output, left ventricular pressure, arterial pressure or rate of change in left ventricular relaxation (-dP/dt) before or after bypass was terminated, while the rate of change in left ventricular contraction (+dP/dt) was lower in the amiodarone-treated pigs. The time on bypass, before stable hemodynamics had recovered, was prolonged in amiodarone-treated animals, 46 +/- 4 min versus 31 +/- 3 min in the controls (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial fibrillation and flutter after coronary artery bypass surgery: epidemiology, risk factors and preventive trials

Atrial fibrillation and atrial flutter are common arrhythmias after coronary artery bypass grafting. Although the consequences of the arrhythmia are generally not life-threatening, it constitutes a major clinical problem often requiring conversion to sinus rhythm. Atrial fibrillation or flutter can result in hypotension, heart failure, pneumonia, and stroke. This article reviews the literature on epidemiology, electrophysiology, risk factors, and preventive trials. The major conclusions are: (1) In patients undergoing coronary artery bypass surgery, the incidence of postoperative atrial fibrillation or flutter is 20-30%, the peak incidence being on the second or third postoperative day. (2) The strongest independent preoperative predictor for atrial fibrillation or flutter is the patients' age. (3) Intra-atrial conduction delay recorded pre and peroperatively may predict development of atrial fibrillation. (4) Peroperative inducibility of atrial fibrillation by pacing the right atrium may identify patients at risk for postoperative atrial fibrillation. (5) Development of postoperative atrial fibrillation or flutter has not been associated with peroperative or postoperative events. (6) The specificity and sensitivity of age and other possible relevant factors for prediction of atrial fibrillation or flutter after coronary artery bypass grafting is low. (7) No effective prophylactic regimen has yet been established.

Reduced cardiac reserve in amiodarone-treated pigs after cardiopulmonary bypass and cardioplegic arrest

An animal model was designed for blinded study to elucidate whether cardiac pump failure after heart surgery in amiodarone-treated patients is due to interference between the drug and the surgical procedures. Seventeen adult pigs were treated with amiodarone for 30 days (study animals, 1,400 mg/day, n = 9; untreated control animals, n = 8) followed by exposure to cardiopulmonary bypass and topical cold cardioplegic arrest (Bretschneiders solution) for 60 min. Apart from 1 g of calcium, no inotropic agents were administered. Cardiac reserve was tested by ventricular pacing (200 beats/min for 30 min or until exhaustion). No difference in hemodynamic status was observed between the treated and the untreated group before pacing. Pacing duration in the amiodarone-treated pigs was 10 +/- 3 versus 22 +/- 4 min in control pigs (p less than 0.05). Only one amiodarone-treated pig survived 30 min of pacing compared with five control pigs (11% vs. 63%, p less than 0.05). The following variables differed significantly in the two groups during pacing: cardiac output, left ventricular pressure, arterial pressure and peak positive and negative first derivative of left ventricular pressure (dP/dt). Most marked were the changes in peak positive dP/dt, indicating a compromised systolic function. The two groups did not differ in preload or afterload at any time during the experiments.

Two-dimensional color-mapping of turbulent shear stress distribution downstream of two aortic bioprosthetic valves in vitro

Since artificial heart valve related complications such as thrombus formation, hemolysis and calcification are considered related to flow disturbances caused by the inserted valve, a thorough hemodynamic characterization of heart valve prostheses is essential. In a pulsatile flow model, fluid velocities were measured one diameter downstream of a Hancock Porcine (HAPO) and a Ionescu-Shiley Pericardial Standard (ISPS) aortic valve. Hot-film anemometry (HFA) was used for velocity measurements at 41 points in the cross-sectional area of the ascending aorta. Three-dimensional visualization of the velocity profiles, at 100 different instants during one mean pump cycle, was performed. Turbulence analysis was performed as a function of time by calculating the axial turbulence energy within 50 ms overlapping time windows during the systole. The turbulent shear stresses were estimated by using the correlation equation between Reynolds normal stress and turbulent (Reynolds) shear stress. The turbulent shear stress distribution was visualized by two-dimensional color-mapping at different instants during one mean pump cycle. Based on the velocity profiles and the turbulent shear stress distribution, a relative blood damage index (RBDI) was calculated. It has the feature of combining the magnitude and exposure time of the estimated shear stresses in one index, covering the entire cross-sectional area. The HAPO valve showed a skewed jet-type velocity profile with the highest velocities towards the left posterior aortic wall. The ISPS valve revealed a more parabolic-shaped velocity profile during systole. The turbulent shear stresses were highest in areas of high or rapidly changing velocity gradients. For the HAPO valve the maximum estimated turbulent shear stress was 194 N m-2 and for the ISPS valve 154 Nm-2. The RBDI was the same for the two valves. The turbulent shear stresses had magnitudes and exposure times that might cause endothelial damage and sublethal or lethal damage to blood corpuscules. The RBDI makes comparison between different heart valves easier and may prove important when making correlation with clinical observations.

Three-dimensional visualization of velocity profiles in the porcine abdominal aortic trifurcation

To study the local distribution of blood velocities in the abdominal aorta and trifurcation, hot-film anemometry was used for point blood velocity measurements in the entire cross-sectional area in the abdominal aorta and abdominal aortic trifurcation in pigs weighing 90 kg. The geometry was visualized by use of a casting procedure. General hemodynamic and geometric parameters in the abdominal aorta were comparable to values found in humans. The porcine trifurcation differed somewhat from the human bifurcation. The velocity measurements in the abdominal aorta showed consistently skewed velocity profiles with the highest velocities at the anterior vessel wall. No signs of developed turbulence were found. Velocity measurements in the external iliac vessels showed high velocities at the flow divider, and low velocities with signs of retrograde flow during part of diastole at the lateral vessel wall.

Nonpharmacologic treatment of supraventricular and ventricular tachyarrhythmias. A review of 249 consecutive patients

Incapacitating or life-threatening tachyarrhythmias were treated nonpharmacologically in 249 patients from 1982 to 1991. Among 92 patients surgically treated for supraventricular tachycardia the cure rate was 93% and the complication rate 12%. Radiofrequency catheter ablation gave an equal cure rate in 51 patients, but with no major complications or mortality. Direct-current catheter ablation of the His bundle was successful in 96% of 27 patients with drug-refractory atrial fibrillation or other supraventricular tachyarrhythmias. Among 64 patients undergoing surgery for ventricular tachycardia/ventricular fibrillation, the perioperative mortality was 9%, estimated 5-year survival 69% and estimated 5-year freedom from the preoperative arrhythmias 72%. Of 18 patients treated with implantable cardioverter defibrillator, three (18%) died of heart failure during follow-up. Nonpharmacologic treatment of tachyarrhythmias is concluded to be effective and often definitively curative. The safety-risk ratio is improving as new treatment modalities are developed.

Quantitation of the turbulent stress distribution downstream of normal, diseased and artificial aortic valves in humans

Damage to blood corpuscles seems to be related to the magnitude and exposure time of the turbulent shear stresses (TSS). According to in vitro studies the critical TSS level for lethal erythrocyte and thrombocyte damage is 150-400 N/m2, for exposure times within physiological ranges. To study the distribution of TSS in the human ascending aorta, a hot-film anemometer needle probe was used to register blood velocities at 41 evenly distributed measuring points in the cross-sectional area 5-6 cm downstream of the aortic annulus. Measurements were made in the ascending aorta after normal aortic valves (prior to coronary bypass surgery), after stenotic aortic valves, and after implantation of either St. Jude Medical or Starr Edwards Silastic Ball valves. Three-dimensional visualization of velocity profiles were performed and Reynolds normal stresses (RNS) were calculated within 50-ms overlapping time windows in systole. By coordinating the mean RNS for each time window and for all 41 measuring points, 2-dimensional color-coded mapping of the RNS distribution was made. Based on the velocity profiles and the RNS distribution a relative blood damage index (RBDI) was calculated to incorporate the magnitude and exposure time for RNS in the entire cross-sectional area into one parameter. Turbulent shear stresses were estimated by using a previously determined correlation equation between RNS and TSS. After normal aortic valves, RNS was below 4 N/m2.(ABSTRACT TRUNCATED AT 250 WORDS)

Velocity field studies at surgically imposed arterial stenoses on the abdominal aorta in pigs

In order to describe velocity profiles and the size of deterministic and non-deterministic velocity disturbances at arterial stenoses, symmetrical and asymmetrical stenoses with intended area reductions of 50% ('moderate') and 85% ('severe') were applied on the abdominal aorta in six pigs. Blood velocities were registered by hot-film anemometry in 21 measuring points distributed across the vessel cross-sectional area in one pre-stenotic and three post-stenotic positions. Signal analysis included ensemble averaging, the high-pass filtering technique, and three-dimensional visualization. None of the stenoses affected the pre-stenotic velocity field. Downstream moderate stenoses flow separation and vortex formation were present. Moderate asymmetric stenoses induced turbulence in the post-stenotic velocity field. Immediately downstream of severe stenoses a prominent post-stenotic jet was present. Farther downstream, a multitude of coherent vortices and turbulence dominated the flow field. The transverse distribution of turbulence intensity paralleled with the peak systolic velocity profile, whereas transverse profiles of the relative turbulence intensity (turbulence intensity/mean velocity) revealed peak values in flow field locations with high velocity gradients. Velocity parameters for symmetric and asymmetric severe stenoses were highly comparable. However, the exact degree of stenosis was significantly higher for symmetrical (85%) than for asymmetrical (76%) stenoses. Therefore, recalling that stenosis severity strongly influences the development of velocity disturbances, this indicates that asymmetry of a stenosis is a predictor for blood velocity disturbances.

Placebo-controlled, double-blind study of the effect of verapamil in intermittent claudication

The clinical effect of verapamil was tested in 24 patients with intermittent claudication in a randomized, placebo-controlled, double-blind, crossover study. Slow-release verapamil or placebo was given for two periods of three weeks. The walking distance, systemic blood pressure, and ankle-brachial blood pressure index were measured. Furthermore, a possible change in peripheral vascular tone was provoked by hyperventilation. The walking distance rose after both verapamil (40%) and placebo (31%) (p less than 0.01 for both) but tended to increase only after verapamil (7%) as compared with placebo. Blood pressure fell equally after both verapamil and placebo (p less than 0.05 for both). Verapamil did not influence the ankle-branchial blood pressure index. No signs of vasoactivity in the lower extremities were seen after hyperventilation. Although the greatest individual improvements in walking distance were seen after verapamil administration, it was not possible to predict positive responders among the patients.

Estimation of turbulent shear stresses in pulsatile flow immediately downstream of two artificial aortic valves in vitro

Measuring turbulent shear stresses is of major importance in artificial heart valve evaluation. Bi- and unidirectional fluid velocity measurements enable calculation of Reynolds shear stress [formula: see text] and Reynolds normal stress [formula: see text]. tau is important due to the relation to hemolysis and thrombus formation, but sigma is the only obtainable parameter in vivo. Therefore, determination of a correlation factor between tau and sigma is pertinent. In a pulsatile flow model, laser Doppler (LDA) and hot-film (HFA) anemometry were used for simultaneous bi- and unidirectional fluid velocity measurements downstream of a Hall Kaster and a Hancock Porcine aortic valve. Velocities were registered in two flow field locations and at four cardiac outputs. The velocity signals were subjected to analog signal processing prior to digital turbulence analysis, as a basis for calculation of tau and sigma. A correlation factor of 0.5 with a correlation coefficient of 0.97 was found between the maximum Reynolds shear stress and Reynolds normal stress, implying [formula: see text]. In vitro estimation of turbulent shear stresses downstream of artificial aortic valves, based on the axial velocity component alone, seems possible.

Turbulent stresses downstream of porcine and pericardial aortic valves implanted in pigs

Because late valve-related complications such as hemolysis and thromboembolic events are considered related to flow disturbances caused by the inserted valve, velocity fields downstream of aortic valve prostheses were studied in pigs. Acute hemodynamic evaluation of size 25-mm porcine and pericardial aortic valve prostheses 1 diameter downstream of the valve ring was performed using dynamic three-dimensional visualization of velocity profiles and spatial distribution of turbulence. Point blood velocity signals obtained with a 1-mm hot-film anemometer needle probe were used to compute Reynolds normal stresses (RNS) by calculation of the turbulent velocity energy of the axial velocity component in the systole. The porcine valves caused a skewed velocity and turbulence profile revealing mean spatial systolic RNS at 70 nm-2 +/- 35 nm-2 (+/- SD). The spatial maximum RNS was 275 +/- 139 nm-2. Corresponding values for the pericardial valves were 20 +/- 11 nm-2 and 72 +/- 46 nm-2. The pericardial valves revealed plug-shaped velocity profiles and turbulent profiles with slightly higher RNS values at the stent posts. From a hemodynamic point of view, these acute studies indicate superiority of the pericardial valves compared to the porcine valves. The turbulent stresses found in this study are of a magnitude that may cause blood corpuscular and endothelial damage.

Surgical repair of ruptured aortic sinus of Valsalva aneurysm

Surgical repair of ruptured aortic sinus of Valsalva aneurysm was performed on six patients. The NYHA functional class was I in one case, II in three and III in two cases. All aneurysms had ruptured into the right atrium. Three originated from the right, and three from the non-coronary aortic sinus of Valsalva. The preoperative shunt was 55-200% (mean 118%) of the peripheral cardiac output. At aneurysmal repair, closure of secundum-type atrial septal defect was performed in one case and insertion of a St Jude Medical aortic valve in another. There were no perioperative deaths. Five patients were asymptomatic in the follow-up period (5 months-17 years). One patient died of cardiomyopathy 11 years postoperatively. The long-term results after surgical repair of ruptured aortic sinus of Valsalva aneurysm thus were good, and early operation is recommended in order to avoid congestive heart failure.

Curative surgical treatment of atrioventricular junctional re-entrant tachycardia by perinodal dissection

The medical treatment of an atrioventricular junctional (AV-nodal) re-entrant tachycardia (AVJRT) is often ineffective due to failure of response or significant side effects. Recently, reports of curative surgical procedures using either dissection or cryocoagulation in the AV node area with preservation of normal AV conduction, have been published with excellent short term results in small series. The present paper describes our experience of surgical treatment using the dissection method in five patients. In all patients, AVJRT with short retrograde conduction intervals was diagnosed during the pre- and intraoperative electrophysiological studies. The earliest site of atrial activation during tachycardia was seen close to the triangle of Koch, antero-medially to the AV node. Elective open heart surgery was performed and after cold cardioplegic arrest, the right atrial endocardium was incised and the perinodal atrium carefully disconnected from the AV node. After surgery, a tachycardia could not be induced in any of the patients. In a follow-up period of 14-29 months, all patients have been free of symptoms without antiarrhythmic drugs. Early electrophysiological evaluation of patients with supraventricular tachycardia is advocated and in patients with medically refractory AVJRT, surgery is recommended.

Three-dimensional visualization of velocity profiles in the ascending aorta in humans. A comparative study among normal aortic valves, St. Jude Medical and Starr-Edwards Silastic Ball valves

Blood velocities were recorded intraoperatively in the ascending aorta approximately 6 cm downstream of the aortic annulus in eight patients with normal aortic valves (prior to coronary bypass surgery) and in seven patients after implantation of a St. Jude Medical valve (4) or Starr-Edwards Silastic Ball valve (3) in the aortic position by means of constant temperature hot-film anemometry. The velocities were measured during 5-15 heart cycles at 41 predetermined measurement points almost evenly distributed in the cross sectional area. Velocity profiles were visualized three-dimensionally at 100 time intervals during one mean heart cycle. The standard deviation of velocities was correspondingly three-dimensionally visualized. For the patients with normal aortic valves the velocity profiles were generally flat but skew, with the highest velocity closer to the left vessel wall at the start of systole. During systole the skewness turned counter-clockwise with the highest velocities closer to the posterior, right and finally anterior vessel wall at the end of systole. In patients with an artificial heart valve in the aortic position the design of the valve was reflected on the contour of the profiles. The findings correspond well with model studies.

Analysis of velocity in the ascending aorta in humans. A comparative study among normal aortic valves, St. Jude Medical and Starr-Edwards Silastic Ball valves

To analyze velocity spectral energy distribution in humans, blood velocities were recorded by means of hot-film anemometry at 41 predetermined measurement points in the cross-sectional area of the ascending aorta approximately 6 cm downstream of the aortic valves. Measurements were made in 8 patients with normal aortic valves, in 4 after insertion of a St. Jude Medical (SJM) aortic valve and in 3 after insertion of a Starr-Edwards Silastic Ball (SSB) aortic valve. Data analysis based on Fast Fourier Transform demonstrated that turbulence energy was lower in patients with normal aortic valves than in patients after insertion of an artificial valve in the aortic position and probably more pronounced after SSB valves than after SJM valves. The spatial distribution of the turbulence energy above 100 Hz was more irregular than corresponding laminar velocities previously presented. The VER100 (Velocity Energy Ratio at 100 Hz, i.e. the velocity energy above 100 Hz divided by the total velocity energy) proved useful for evaluating differences in flow disturbances downstream of different aortic valves. The mean VER100 in the three categories of patients were respectively 0.3, 1.4, and 2.1%.

Velocity fields and turbulent stresses downstream of biological and mechanical aortic valve prostheses implanted in pigs

Since detailed knowledge about velocity fields downstream of heart valve prostheses obtained from in vitro studies has not been followed up by similar detailed studies in vivo a pig model for acute velocity field studies downstream of aortic valve prostheses was established. Two mechanical and two bioprosthetic valves were studied and a dynamic three dimensional visualisation of velocity fields one diameter downstream performed under different haemodynamic conditions in a total of 22 pigs. The Ionescu-Shiley pericardial valve had velocity fields very similar to the normal native porcine aortic valve. The Edwards-Carpentier porcine valve caused a jet type flow, and the valve design of the St Jude Medical and Björk-Shiley Monostrut valves was reflected in the velocity profile. Normalised (mean(SEM] systolic Reynolds normal stresses in the total cross sectional area were: native porcine 15(1.5) Nm-2; St Jude Medical 24(3.4) Nm-2; Björk-Shiley Monostrut 25(1.6) Nm-2; Edwards-Carpentier Supra-annular 51(6.6) Nm-2; Ionescu-Shiley Pericardial 19(2.0) Nm-2. Reynolds normal stresses were higher in areas of rapidly changing or constantly high velocity gradients.

A model for acute haemodynamic studies in the ascending aorta in pigs

Since data on velocity fields in the ascending aorta downstream of normal aortic valves in pigs have not yet been obtained velocity profiles were visualised using a hot film anemometer needle probe before and after total cardiopulmonary bypass and cold cardioplegic arrest. Furthermore, measurements were made during increased heart rate and cardiac output. A dynamic three dimensional visualisation of velocity fields showed a skewed clockwise rotating velocity profile, developing from peak systole and continuing throughout the systolic deceleration phase. This pattern was consistent regardless of the haemodynamic state. Heart rate was increased to 180 beats.min-1 and cardiac output by a maximum of 91%. It is concluded that the pig model is valuable for haemodynamic studies in the ascending aorta before and after cold cardioplegic arrest and that the velocity profiles found in this study are important basic data for velocity field studies downstream of artificial heart valves implanted in the aortic position.

Tetralogy of Fallot associated with anomalous origin of the left coronary artery from the pulmonary artery, pulmonary artery hypoplasia and atrial septal defect. A case report

A 7-year-old girl had tetralogy of Fallot with anomalous origin of the left coronary artery from the pulmonary artery, pulmonary artery hypoplasia and atrial septal defect. The case is presented and diagnostic and surgical implications are discussed.

Three-dimensional visualization of axial velocity profiles downstream of six different mechanical aortic valve prostheses, measured with a hot-film anemometer in a steady state flow model

Hot-film anemometry was used for in vitro steady-state measurements downstream of six mechanical aortic valve prostheses at flow rates 10, 20 and 30 l.min-1. Three-dimensional visualizations of velocity profiles at two downstream levels were made with the valves rotated 0 and 60 degrees in relation to the sinuses of valsalvae. The velocity fields downstream of the disc valves were generally skew with increasing velocity gradients and laminar shear stresses with increasing flow rates. Furthermore, increased skewness of the velocity profiles was noticed when the major orifices of the disc valves were towards the commissure than when approaching a sinus of valsalvae. The velocity profiles downstream of the ball valve were generally flat but with considerably more disturbed flow, consistent with the findings in turbulent flow.

Continuous registration of cardiac output with a new computer system designed for hot-film anemometry: an in vitro study

We have developed and improved a method for the continuous on-line registration of cardiac output. By measuring blood velocity with a hot-film anemometer probe in the pulmonary artery, cardiac output can be estimated by gated systolic integration of the velocity signals. The integrated value for a certain period can be converted to a cardiac output proportional value. A thermistor placed next to the velocity probe enables thermodilution measurement of cardiac output, which serves as in vivo and in situ calibration. In this paper an in vitro study of the method applied to pulsatile flow is presented. A good correlation was found between real flow and both the velocity method and the thermodilution method. Fluid temperature and changing stroke volume and/or pulse frequency had minimal influence on accuracy, whereas altered probe position required recalibration for the velocity method but not for the thermodilution method. The advantages of the velocity method for the measurement of cardiac output are: The continuous on-line monitoring of cardiac output. The need for the injection of only very small volumes of cold saline, as the frequency of thermodilution measurements is reduced.

Verapamil induced increment of oxygen extraction in the arteriosclerotic limb

The acute effect of intravenously administered verapamil (0.08 mg X kg-1 body weight, mean dose 5.1 +/- 0.7 mg) on oxygen exchange and arterial blood flow (measured electromagnetically) of the lower limb was studied during reconstructive arterial surgery in 17 patients with obliterative arterial disease of the lower limbs. Verapamil increased oxygen extraction in the diseased leg by 12% (from a median value of 28.3 to 31.6 ml X litre-1, p less than 0.01) whereas it had no effect on arterial blood flow. The increment of oxygen extraction after drug administration correlated negatively with the walking distance of the patients (r = 0.69, p less than 0.01). Systolic and diastolic blood pressure decreased significantly by 10% and 6%, respectively, whereas heart rate remained unchanged after the administration of verapamil. The results suggest that verapamil might be beneficial in the treatment of patients with intermittent claudication, despite the fact that no vasodilatation was seen after the drug.