Attila Kardos

Value of Delayed-Enhancement Cardiovascular Magnetic Resonance Imaging in Predicting Myocardial Viability After Surgical Revascularization

Background—Despite the accepted utility of delayed-enhancement MRI in identifying irreversible myocardial injury, no study has yet assessed its role as a viability tool exclusively in the setting of coronary artery bypass surgery (CABG), and no study has repeated delayed-enhancement MRI late after revascularization. In a clinical trial in which patients underwent CABG by either the off-pump or on-pump surgical technique, we hypothesized that (1) preoperative delayed-enhancement MRI would have high diagnostic accuracy in predicting viability and (2) the occurrence of perioperative myocardial necrosis would affect late regional wall motion recovery. Methods and Results—Fifty-two patients undergoing multivessel CABG were studied by preoperative and early (day 6) and late (6 months) postoperative cine MRI for global and regional functional assessment and delayed-enhancement MRI for assessment of irreversible myocardial injury. Preoperatively, 611 segments (21%) had abnormal regional function, whereas 421 segments (14%) showed evidence of hyperenhancement. At 6 months after revascularization, 57% (343 of 611) of dysfunctional segments improved contraction by at least 1 grade. When all preoperative dysfunctional segments were analyzed, there was a strong correlation between the transmural extent of hyperenhancement and the recovery in regional function at 6 months (P<0.001). Of a total of 96 previously dysfunctional but nonenhancing or minimally hyperenhancing myocardial segments that did not improve regional function at 6 months, 35 (36%) demonstrated new perioperative hyperenhancement in the early postoperative MRI scan. Conclusions—Delayed-enhancement MRI is a powerful predictor of myocardial viability after surgery, suggesting an important role for this technique in clinical viability assessment.

Effects of Off-Pump Versus On-Pump Coronary Surgery on Reversible and Irreversible Myocardial Injury A Randomized Trial Using Cardiovascular Magnetic Resonance Imaging and Biochemical Markers

Background—There is biochemical evidence that off-pump coronary artery bypass grafting (OPCABG) reduces myocardial injury compared with the use of cardiopulmonary bypass (ONCABG), but the functional significance of this is uncertain. We hypothesized that OPCABG surgery would result in reduced postoperative reversible (stunning) and irreversible myocardial injury, as assessed by cardiovascular MRI (CMRI). Methods and Results—In a single-center randomized trial, 60 patients undergoing multivessel total arterial revascularization were randomly assigned: 30 to OPCABG and 30 to ONCABG. Patients underwent preoperative and early postoperative cine MRI for assessment of global left ventricular function, and contrast-enhanced CMRI for assessment of irreversible myocardial injury. Serial troponin I measurements were obtained perioperatively and correlated with the CMRI findings. The mean preoperative cardiac index was similar in the 2 surgical groups (2.9±0.7 ONCABG; 2.9±0.8 OPCABG; P =0.9). After surgery, the cardiac index was significantly higher in the OPCABG group (2.7±0.6 ONCABG; 3.2±0.8 OPCABG; P =0.04). New irreversible myocardial injury was similar in incidence (36% ONCABG; 44% OPCABG; P =0.8) and magnitude (6.3±3.6 g ONCABG; 6.8±4.0 g OPCABG; P =0.9) across the 2 groups. The median area-under-the-curve (AUC) troponin I values were significantly larger in the ONCABG group (182 versus 135 &mgr;g/L; P =0.02). There was a moderate correlation between the troponin I AUC values and mean mass of new myocardial hyperenhancement (r2=0.4; P =0.008). Conclusions—OPCABG results in significantly better left ventricular function early after surgery but does not reduce the incidence or extent of irreversible myocardial injury.

Determinants of Spontaneous Baroreflex Sensitivity in a Healthy Working Population

Baroreflex sensitivity (BRS) by the spontaneous sequence technique has been widely used as a cardiac autonomic index for a variety of pathological conditions. However, little information is available on determinants of the variability of spontaneous BRS and on age-related reference values of this measurement in a healthy population. We evaluated BRS as the slope of spontaneous changes in systolic blood pressure (BP) and pulse interval from 10 minutes BP (Finapres) and ECG recordings in 1134 healthy volunteers 18 to 60 years of age. Measurement of BRS could be obtained in 90% of subjects. Those with unmeasurable spontaneous BRS had a slightly lower heart rate but were otherwise not different from the rest of the population. BRS was inversely related to age (lnBRS, 3.24−0.03×age;r2=0.23;P <0.0001) in both genders. In addition, univariate analysis revealed a significant inverse correlation between BRS and heart rate, body mass index, and BP. Sedentary lifestyle and regular alcohol consumption were also associated with lower BRS. However, only age, heart rate, systolic and diastolic BP, body mass index, smoking, and gender were independent predictors of BRS in a multivariate model, accounting for 47% of the variance of BRS. The present study provides reference values for spontaneous BRS in a healthy white population. Only approximately half of the variability of BRS could be explained by anthropometric variables and common risk factors, which suggests that a significant proportion of interindividual differences may reflect genetic heterogeneity.

Epidemiology of congenital coronary artery anomalies: A coronary arteriography study on a Central European population

The anatomical patterns and frequency of occurrence of congenital coronary anomalies (CCA) in a Central European cohort has not yet been studied. The angiographic data of 7,694 consecutive patients undergoing coronary arteriography at the Albert Szent-Györgyi Medical University, Szeged, Hungary, from 1984 to 1994 were analyzed. CCA were found in 103 patients (1.34% incidence). Ninety-eight of them (95.2%) had anomalies of origin and distribution, and five (4.8%) had coronary artery fistulae. The incidence was the highest for the separate origin of left descending artery and left circumflex from the left sinus of Valsalva (52.42%). Anomalous origin of the left circumflex coronary artery from the right coronary was 8.7% while from the right sinus of Valsalva 18.4%. CCA, which may be associated with potentially serious events, such as ectopic coronary origin from the opposite aortic sinus (1.9%) and single coronary arteries (3.88%), were not frequent. The incidence of CCA in the Central European cohort under study was similar to that of the largest North American study. The anatomic classification presented can be useful from both clinical and surgical standpoints.

Identification of higher brain centres that may encode the cardiorespiratory response to exercise in humans

1 Positron emission tomography (PET) was used to identify the neuroanatomical correlates underlying ‘central command’ during imagination of exercise under hypnosis, in order to uncouple central command from peripheral feedback. 2 Three cognitive conditions were used: condition I, imagination of freewheeling downhill on a bicycle (no change in heart rate, HR, or ventilation, V̇I): condition II, imagination of exercise, cycling uphill (increased HR by 12 % and V̇I by 30 % of the actual exercise response): condition III, volitionally driven hyperventilation to match that achieved in condition II (no change in HR). 3 Subtraction methodology created contrast A (II minus I) highlighting cerebral areas involved in the imagination of exercise and contrast B (III minus I) highlighting areas activated in the direct volitional control of breathing (n= 4 for both; 8 scans per subject). End‐tidal PCO2 (PET,CO2) was held constant throughout PET scanning. 4 In contrast A, significant activations were seen in the right dorso‐lateral prefrontal cortex, supplementary motor areas (SMA), the right premotor area (PMA), superolateral sensorimotor areas, thalamus, and bilaterally in the cerebellum. In contrast B, significant activations were present in the SMA and in lateral sensorimotor cortical areas. The SMA/PMA, dorso‐lateral prefrontal cortex and the cerebellum are concerned with volitional/motor control, including that of the respiratory muscles. 5 The neuroanatomical areas activated suggest that a significant component of the respiratory response to ‘exercise’, in the absence of both movement feedback and an increase in CO2 production, can be generated by what appears to be a behavioural response.

Baroreceptor stimulation: Pain perception and sensory thresholds

Baroreceptor activity has been implicated in the modulation of pain. Sensory detection thresholds and pain ratings were measured in a group of 28 men during carotid baroreceptor manipulation with the PRES (phase-related external suction) neck suction technique. Brief, cardiac phase-related electrical impulses were delivered intracutaneously to the finger. The results indicate that minimum baroreceptor activity was associated with more severe pain, but had no effect on sensory detection threshold. The results are discussed in terms of the learned model of hypertension.

Circulatory Support for Long-Term Treatment of Heart Failure Experience With an Intraventricular Continuous Flow Pump

Background—A lifetime mechanical solution for advanced heart failure must be reliable, with a low risk of life-threatening complications. After extensive laboratory testing, we began clinical trials with an axial flow pump for long-term treatment of New York Heart Association class IV, transplant-ineligible patients. Methods and Results—The Jarvik 2000 is a continuous flow device that is implanted in the apex of the left ventricle with offloading to the descending thoracic aorta. Skull-based percutaneous power delivery was derived from cochlear implant technology. We used this system in 4 patients with end-stage dilated cardiomyopathy. Exercise capacity, quality of life, device parameters, and native heart function were monitored serially. One patient died from right heart failure at 3 months. The other patients were discharged from hospital between 3 and 8 weeks postoperatively and are currently New York Heart Association I or II. Follow-up lasted between 9 and 20 months. There has been no device failure or hemolysis. Native heart function and quality of life were markedly improved. Conclusions—The Jarvik 2000 is a true assist (rather than replacement) device that functions synergistically with the native left ventricle and provides excellent quality of life. Adverse events are infrequent. This blood pump may provide a mechanical solution for end-stage heart failure in the community.

Effect of exogenous nitric oxide on baroreflex function in humans

Nitric oxide (NO) donors inhibit sympathetic neurotransmission and baroreceptor activity and can directly stimulate heart rate (HR) in vitro. To assess whether exogenous NO affects cardiovascular autonomic control in humans, we tested the baroreceptor-cardiac reflex [baroreflex sensitivity (BRS)] and the arterial blood pressure (BP) and HR variability during an infusion of the NO donor sodium nitroprusside (SNP, 2 micrograms . kg(-1). min(-1)) or 5% glucose in 16 healthy subjects. The hypotensive action of SNP was prevented by phenylephrine (PE, 0.9 +/- 0.15 micrograms . kg(-1). min(-1)). The SNP + PE infusion did not affect BRS or HR variability, but it caused a significant reduction in the diastolic and systolic BP low-frequency power. In addition, SNP + PE caused a sustained 12% increase in HR in the absence of changes in brachial and aortic BP. In conclusion, SNP had no effect on the cardiac-vagal limb of the baroreflex in humans but caused a substantial reduction in BP low-frequency power consistent with a decreased baroreflex/sympathetic control of peripheral resistance. The increase in HR in the absence of baroreceptor downloading confirms our previous finding of a direct positive chronotropic effect of NO donors.

Heterozygous disruption of SERCA2a is not associated with impairment of cardiac performance in humans: implications for SERCA2a as a therapeutic target in heart failure

Objective: To verify whether a deficiency in the cardiac sarcoplasmic reticulum pump SERCA2a causes cardiac dysfunction in humans. Design: Cardiac performance was measured in a serendipitous human model of primary SERCA2a deficiency, Darier’s disease, an autosomal dominant skin disorder caused by mutations inactivating one copy of the ATP2A2 gene, which encodes SERCA2a. Methods: Systolic and diastolic function and contractility were assessed by echocardiography at rest and during exercise in patients with Darier’s disease with known mutations. Fourteen patients with Darier’s disease were compared with 14 normal controls and six patients with dilated cardiomyopathy with stable heart failure. Results: Resting systolic and diastolic function was normal in patients with Darier’s disease and in controls. The increase in systolic function during exercise was not different between patients with Darier’s disease and normal controls; neither was there a difference in contractility. As expected, patients with dilated cardiomyopathy had impaired diastolic and systolic function with depressed contractility at rest and during exercise. Conclusion: Contrary to expectations, heterozygous disruption of SERCA2a is not associated with the impairment of cardiac performance in humans. Attempts to increase SERCA2a levels in heart failure, although showing promise in rodent studies, may not be addressing a critical causal pathway in humans.

Anteroseptal or Apical Myocardial Infarction: A Controversy Addressed Using Delayed Enhancement Cardiovascular Magnetic Resonance Imaging

AIM Delayed enhancement MRI (DE-MRI) of the heart has been shown to reliably identify areas of irreversible myocardial damage. We sought to determine if the term anteroseptal MI is appropriate by correlating electrocardiographic, angiographic, cine MRI and DE-MRI findings. METHODS AND RESULTS Nineteen patients admitted to our hospital with their first acute anterior MI and whose ECG showed new Q waves in leads V1-V4 were studied. All patients underwent cardiac catheterization, cine MRI, and DE-MRI. The mean left ventricular ejection fraction was 53%+/-16%. All 19 patients had evidence of delayed hyperenhancement in one or more myocardial segments (mean number of affected segments 5.5+/-2.1). The mean mass of hyperenhanced myocardium was 14+/-8 grams, or 10%+/-6% of absolute LV mass. Nineteen (100%) and 15 (79%) patients showed evidence of delayed hyperenhancement of the apex and apical anterior segments respectively. Seven (37%) patients showed evidence of mid ventricular anteroseptal hyperenhancement and none had any hyperenhancement of basal anteroseptal segments. CONCLUSION High resolution cardiac MRI applied in patients with acute infarction and new Q waves in leads V1-V4 demonstrates the presence of predominantly apical, but not isolated septal or anteroseptal infarction.