quarta-feira, 15 de junho de 2011

Terapia de Ressincronização Cardíaca - by Fábio Soares

Parafraseando o poeta: "Com certeza, existe algo mais entre o QRS e a Ressincronização cardíaca do que julga a nossa vão eletrocardiografia...".


 Nenhum método sozinho conseguiu selecionar melhor os pacientes paa a CRT que o ECG, porém, não parece ser uma questão dicotômica ECG x demais exames... A combinação dos mesmos deve ser o mais eficaz. A importância da demonstração de viabilidade x cicatriz x posição do eletrodo x anatomia venosa x identificação da área com maior atraso eletromecânico é inegável. Além disso, devemos tentar identificar o momento ideal para a indicação do tratamento, a fronteira entre o "bem demais" e o "ruim denais" para poder se beneficiar da intervenão.


A terapia apresenta alto custo e, a despeito da "adequada seleção" dos pacientes conforme os guidelines, cerca de 30-40% são considerados não respondedores, e uma percentagem destes ainda pioram o quadro clínico. Além disso, a demonstração ecocardiográfica de assincronia em pctes com QRS estreito pode sugerir que estes pacientes deixem de receber uma terapia possivelmente benéfica... Há muito ainda a ser discutido.

CRT: No clinical benefit seen in "moderately" prolonged QRS; many getting it needlessly

Cleveland, OH (updated) - Two-fifths of heart-failure patients who receive cardiac resynchronization therapy (CRT) aren't benefiting clinically from the device therapy because the guidelines-specified electrocardiographic criteria for eligibility are too broad, according to the authors of a new meta-analysis of the major CRT trials [1].
Based on those same trials, among others, current guidelines recommend [2] in the strongest terms that CRT be offered to patients with a QRS >120 ms (assuming they meet LVEF requirements and other criteria), observed the study's lead author, Dr Ilke Sipahi (University Hospitals and Case Medical Center, Cleveland, OH), for heartwire.
But his group's meta-analysis indicates that essentially the only patients who gained clinically in those trials—with better survival and lower risk of heart-failure hospitalization, for example—were those with a baseline QRS interval of at least 150 ms. And that was regardless of symptom status, according to Sipahi. "You see it all along the NYHA functional class spectrum."

Doubts about QRS criteria aren't new
A falloff in CRT effectiveness has long been observed in patients with only moderately prolonged QRS intervals, in individual trials and even in clinical practice, according to Sipahi. It's been talked about, but seldom if ever has the literature previously proposed that CRT may not work when the QRS is in the 120-150 range, he said.
His group's report, published online June 13, 2011 in the Archives of Internal Medicine, justifies a revisiting of QRS requirements for CRT, Sipahi said. "This is not a subgroup analysis of a single trial. Five different subgroup analyses [in five separate trials] have shown the exact same thing over the course of a decade."
"Among patients with a QRS greater than 120 ms, 40% of them have a QRS between 120 ms and 150 ms. So four out of 10 CRT devices are unnecessary." In such cases, he proposed, CRT may even be worse than no CRT: "Not only is there no benefit, but these patients are also exposed to unnecessary risks." Potential complications of CRT-device implantation include bleeding, infection, pneumothorax, and lead fracture or dislodgment, "and even death has been reported."
The major cardiology societies, both in North America and Europe, all have guidelines for CRT eligibility based on the QRS interval. "All of them say 120 ms, and all of them are wrong. The guidelines need to change," he said.

"The trials are remarkably congruent . . . "
"Despite the limitations of combining different trials, the results of this meta-analysis are robust enough to anchor a growing suspicion that the patients with QRS in the 120-to-150-millisecond range do not improve after CRT," agrees an accompanying commentary from Dr Lynne Warner Stevenson (Brigham and Women's Hospital, Boston, MA) [3]. "The trials are remarkably congruent, regardless of [heart-failure] clinical class or etiology."
The current analysis "challenges us to reevaluate our approach to CRT," writes Stevenson, who was on the writing committee for the ACC/AHA guidelines that cover CRT for heart failure. "It may now be unethical to recommend and reward this procedure in patients for whom we now have evidence of no benefit."
But another member of guidelines writing committee, Dr William T Abraham (Ohio State University, Columbus), sees the meta-analysis differently. "To say that patients with a QRS less than 150 shouldn't get CRT is the wrong conclusion from this paper," he told heartwire.
First of all, he said, the meta-analysis "is dominated by trials in NYHA class 1-2 heart failure" and so has less to say about the effects of QRS duration in class 3-4 disease.
Moreover, it focuses on clinical outcomes and ignores the positive effects of CRT on symptoms, functional status, exercise capacity, and quality of life, "all of which are important in the treatment of heart failure," he said. "Making patients feel better alone is a reason to use the therapy."
Finally, Abraham agreed that "there are some question marks" about CRT when the QRS interval is in the 120-ms-to-150-ms range but said a meta-analysis isn't the way to answer them.
"Meta-analyses are properly viewed as hypothesis-generating, and the hypothesis should be confirmed in a randomized controlled trial. I don't think they should inform policy making or guideline writing the way that randomized controlled trials do."

QRS intervals and CRT clinical outcomes
Sipahi and his colleagues searched for trials comparing CRT with no CRT on top of optimal medications that reported clinical outcomes across different QRS-interval ranges. They arrived at five that together had randomized 5813 patients, consisting of COMPANION (which enrolled patients in NYHA class 3-4), CARE-HF (NYHA class 3-4), REVERSE (NYHA class 1-2), MADIT-CRT (NYHA class 1-2), and RAFT (NYHA class 2-3). All required patients to have poor LV systolic function (usually LVEF <30% or <35%) and a QRS interval >120—except for MADIT-CRT, in which the threshold was >130 ms. Follow-ups ranged from about one year to more than three years.
Across all five trials, the relative risk reduction for their composite clinical end point—which always included mortality and either all-cause or heart-failure hospitalization—with CRT vs no CRT was 0.95 (95% CI 0.82-1.10) for moderately prolonged baseline QRS (up to about 150 ms) and 0.60 (95% CI 0.53-0.67) when it was severely prolonged (higher than about 150 ms). And, according to the group, "the magnitude of benefit became more prominent with further increases in QRS duration."
It makes mechanistic sense that the CRT benefit with longer QRS intervals should be independent of NYHA functional class, according to Sipahi. Functional class is highly subjective and can vary from day to day in individual patients, he observed. "QRS, on the other hand, is really about the level of dyssynchrony that can be corrected by CRT. And it appears that only patients with a QRS greater than 150 ms have a level of dyssynchrony that can be corrected by CRT."
There may be exceptions to the rule, however. "Nonrandomized studies suggest that echocardiographic parameters of dyssynchrony may help identify patients with moderately prolonged QRS who might respond to CRT," according to Sipahi. Those parameters—for example, radial strain—have been explored primarily in patients with narrow QRS intervals, that is, <120 ms.
"We now know that 120 ms to 149 ms also does not respond, but perhaps there is a subset of those patients [who will respond to CRT] who could be identified by echocardiography. But that's just a hypothesis that needs to be tested."

  1. Sipahi I, Carrigan TP, Rowland DY, et al. Impact of QRS duration on clinical event reduction with cardiac resynchronization therapy. Meta-analysis of randomized controlled trials. Arch Intern Med 2011; DOI:10.1001/archinternmed.2011.247.
  2. Hunt SA, Abraham WT, Chin MH, et al. 2009 Focused update incorporated into the ACC/AHA 2005 guidelines for the diagnosis and management of heart failure in adults. A report of the American College of Cardiology Foundation/American Heart Association task force on practice guidelines developed in collaboration with the International Society for Heart and Lung Transplantation. J Am Coll Cardiol 2009; 53: e1-e90.
  3. Stevenson LW. "A little learning is a dangerous thing." Arch Intern Med 2011; DOI:10.1001/archinternmed.2011.272.

2 comentários:

  1. Também concordo com você Fabio. É muito improvável, ou ilmplausivel que um método que visualiza o processo mecânico da contração em tempo real nao tenha utilidade nesta avaliaçao em especial. Creio que ainda nao se encontrou o ponto ou os pontos relevantes a serem observados. Por exemlo, falamos em movimento assincronicp do septo, mas na pratica você já viu quantos tipos diferentes deles existem? Nao da pra botar tudo no mesmo saco e achar que é uma coisa sô. Nem sempre tudo se resume a ter ou nao ter, mas há um como que pode fazer toda a diferença. Isto só pra começar... Depois tem o fato de que nem sempre vai dar pra avaliar uma parede que nao mexe...ela ta assincronica? Ou ela nao ta nada ?
    Entao realmente ha muito mais coisas nao só para alem do eco, como também dentro dele que precisa melhor investigada....
    Outro ponto muito importante na pratica é: quantos destes nao responsivos fizeram de fato uma otimização dos seus intervalos apos o implante?

    Esta questão exige uma sincronização entre dois grupos de profissionais sempre ultra mega atarefados : o ecografista e o arritmplogo. Alem da presença nem sempre disponível daqueles aparelhinhos ultra mega específicos que apenas os fabricantes de marca-passo tem para disponibilizar: os programadores.

    Nila Costa

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  2. Exatamente, Nila! AInda há muito a se aperfeiçoar. Após o São João virá um post com novidades em CRT! Obrigado pela presença.

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